Pros and cons of valve amps

[plastic penguin]

Have to be honest and say I haven't heard a valve amp for about 30 years. All my amps have been A/B Class, which has always suited the room acoustics and ease of speaker matching blah blah...

Some people say valve or tube amps sound warm, while others descibe them as neutral. I've also read reviews where the overriding theme has been speaker compatibility.

Discuss...

[Reffc]

A valve amp and SS amp, if both are competently designed and rated for the speakers being driven should sound pretty similar. This thing about valve amps sounding "warm" mainly applies to designs which are outputting high distortion either by design or by default! (ie poorly designed and specified).

Class A/B are the most common, in push-pull configuration. Advantages are that if well designed, distortion can be very low indeed and when overdriven some will clip more euphonically than a SS equivalent as distortion is often (but not always) even order. This can make a valve amp sound more meaty for it's rating than you might expect as it will drive into distortion sometimes without some people noticing.

Personally, I've always preferred a well designed valve amp over a SS amp because to my ears, mid range purity of tone just seems "right" but it is highly design dependant and most valve amps are only as good as the output transformers and power supplies that they use. Good output transformers cost £££££'s so you'll rarely get something for nothing where valve amps are concerned and good ones come at a cost.

SS amps can be made more cheaply, but generally, I think it's wise to over rate them to prevent ever running them into clipping which is bad for the health of the drive units, so if you have speakers that are say 87dB sensitive with a 6 Ohm load and the speaker manufacturer says "can be driven with amps of 50wpc or above" I'd double that and look for one that delivers 100wpc minimum.

As for valve amps being speaker sensitive, you rate them accordingly for power output but also check that their output impedance is appropriate. It is no good buying a 15wpc Single Ended valve amp using zero negative feedback with an output impedance of say 3 to 4 Ohms (realistic) if you want to drive a speaker load which has an impedance profile resembling the Alps as the frequency response will swing with impedance. You need a low output impedance from a valve amp to have sufficient damping factor to control bass, not to deliver it (a common misconception is the SE valve amps don't "do" bass...they do and can go very low, but controlling that response depends entirely on the damping factor).

There are good and bad examples of both. You pays your money etc etc...

[Haselsh1]

From my own experience I cannot say that valve amps sound warm and cuddly as folk say they do. I have found that they have a distinct liquid purity and lack of graininess compared to trannies though. Big tranny amps though do slam and guts in the bass by the bucketload which none of my valve amps have ever done. However, I have found that valves do loads of slam in the midrange. I love the purity of their treble though, valves that is.

[farflungstar]

I agree with that last post - my Cary's certainly aren't warm and fuzzy and dont lack bass slam. For me there there's a musicality and purity with SE that SS just can't match. But the cons... All the above is dependent on design and valves used. But the biggest headache is the cost of retubing the things which can be ludicrously expensive if going the ELROG et al route. As someone said, you pays your money....

Adey

In perpetual pursuit.

[Gazjam]

I agree with that last post - my Cary's certainly aren't warm and fuzzy and dont lack bass slam. For me there there's a musicality and purity with SE that SS just can't match. But the cons... All the above is dependent on design and valves used. But the biggest headache is the cost of retubing the things which can be ludicrously expensive if going the ELROG et al route. As someone said, you pays your money....

Adey

In perpetual pursuit.

Hear you on the Elrogs...hoping mine dont need replaced for a LONG time!
Its a SET power amp I have into a SS Pre and sounds good.

No lack of deep bass or slam here, but with the lower powered valve amps you need careful speaker matching to get it to work.

[Arkless Electronics]

The class of amp is completely independent of whether it is valve or SS... Valve amps are much more commonly class A than SS amps (SET's can only be class A) and especially when 50WPC ish or less. SS amps are rarely class A simply because it costs so much... when class A the £/W will be similar to that of a valve amp (as will the size, weight and heat produced!) and people kind of expect SS amps to be much cheaper, Watt for Watt, than a valve amp. This IMHO gives valve amps an "unfair" advantage and is what can sometimes hold back the performance of SS amps.
I could go on all night here and make this the longest post on record in comparing and contrasting the damping factor, frequency response and distortion performance etc etc of valves V SS and all the factors that define the parameters... don't worry I won't!
IMHO the best examples of valve and SS amps will sound pretty much the same in most areas but SS will always have an advantage in the bass due simply to the lack of an output transformer. I don't include SET's here as, whilst many people swear by them, they are intrinsically high distortion and poor damping factor (the latter due mainly to lack of feedback and the former partially) and this will give them the warm, lush sound they are known for and which many people love... but is ultimately a distortion and inaccuracy and so not as hi in fi as other types. The best SET I've personally heard BTW is Gazjams Long Dog Audio unit. See Lurcher (Nick) for one of these...

[walpurgis]

I like and use both. Valve Class A or transistor Class A and I'm equally happy with either in the right context, depends largely on what speakers I'm using though. I certainly don't notice any lack of bottom end punch or grip from what are relatively low powered amps. I would definitely not call my rather obscure EL34 valve monos 'lush' sounding, a touch more euphonic than the SS perhaps, but not much in it.

[Arkless Electronics]

I like and use both. Valve Class A or transistor Class A and I'm equally happy with either in the right context, depends largely on what speakers I'm using though. I certainly don't notice any lack of bottom end punch or grip from what are relatively low powered amps. I would definitely not call my rather obscure EL34 valve monos 'lush' sounding, a touch more euphonic than the SS perhaps, but not much in it.

Same here:) A valve amp certainly doesn't have to be lush sounding.. I've heard the odd one that sounds more "transistory" than most SS amps! In the case of SET's though they will intrinsically have around 5-10 times the distortion of a push pull amp and much of this even order (predominantly second in fact) and this will tend to give a "lush" "warm" effect to anything going through it. Also a valve amp can have superb bass but ultimately is held back here by the transformer. Not to say a valve amp with superb grip and punch cannot be as good as an average to good SS amp but ultimately the cards are all marked in favour of SS when it comes to bass;)

[09mike69]

i've never heard a valve amp, been tempted on occasion to buy one, but then backed off, partly because of price, but mostly due to lack of knowledge.
i was looking at rogers cadet 3 amps until the price went a bit silly.
they were going for about 150-200 quite regular on ebay,, getting a bit scarce now, and fetching nearly double.
snooze you lose i guess.
cheers
Mike.

[Ninanina]

In my experience yes valve amps can indeed sound warm

My 'warm' experiences with valve amps have been with an unmodified pair of Quad II's and with a Chinese Ming Da amp. Other than that the other valve amps I've had do not sound 'warm', just right to me

I will try to list the 'non warm' sounding valve amps I've owned, these are the ones that I can remember

Decware SE84
Rogers E40a
Chinese YAQIN MC-100B KT88 (not 'warm' sounding at all, quite 'sharp' and 'brittle' sounding to me)
Audio Note Conqueror 300b
Oto SE
Meishu

The above are in no particular order

Colin has NVA monoblocls and NVA pre and whenever I listen to his system it sounds great, much punchier sounding and the bass it better than my own system but I still prefer my current SET amps sound

I can't imagine that I will ever go back to ss as I have become so accustomed to the sound of my SET amps and find them the most pleasing sounding to me

When I do listen to ss amps they seem to miss the 'character' and 'feeling' of good valve amps however that might be because I haven't listened to the 'right' ss amps :)

Many many years ago I heard a very expensive system which included some huge Mark Levinson monoblocks and I was completely underwhelmed by the sound and this was probably the most expensive system I have ever heard

However that is just my opinion and my experiences ;)

[walpurgis]

i was looking at rogers cadet 3 amps until the price went a bit silly.
Mike.

Don't bother. They are overrated and as you say, overpriced these days. I had several of them (lost count) when they were dirt cheap. The sound is not unpleasant, but nothing special and they don't pack much punch. For the difference in price, paying extra for a Leak Stereo 20 would be a far smarter move. The Leak sounds lovely, has surprising grip and can hold its own against some pretty serious amps and it works well with a cheap passive pre-amp.

[southall-1998]

In my experience yes valve amps can indeed sound warm

My 'warm' experiences with valve amps have been with an unmodified pair of Quad II's and with a Chinese Ming Da amp. Other than that the other valve amps I've had do not sound 'warm', just right to me

I will try to list the 'non warm' sounding valve amps I've owned, these are the ones that I can remember

1st was a Decware SE84
2nd was the Rogers E40a
3rd was a Chinese YAQIN MC-100B KT88 (not 'warm' sounding at all, quite 'sharp' and 'brittle' sounding to me)
4th was an Audio Note Conqueror 300b
5th is the Oto SE
6th is the Meishu

Colin has NVA monoblocls and NVA pre and whenever I listen to his system it sounds great, much punchier sounding and the bass it better than my own system but I still prefer my current SET amps sound

I can't imagine that I will ever go back to ss as I have become so accustomed to the sound of my SET amps and find them the most pleasing sounding to me

When I do listen to ss amps they seem to miss the 'character' and 'feeling' of good valve amps however that might be because I haven't listened to the 'right' ss amps :)

Many many years ago I heard a very expensive system which included some huge Mark Levinson monoblocks and I was completely underwhelmed by the sound and this was probably the most expensive system I have ever heard

However that is just my opinion and my experiences ;)


The Meishu is a lovely sounding beast. So you rate it as warmer sounding than the Oto SE?

s.

[Ninanina]

Don't bother. They are overrated and as you say, overpriced these days. I had several of them (lost count) when they were dirt cheap. The sound is not unpleasant, but nothing special and they don't pack much punch. For the difference in price, paying extra for a Leak Stereo 20 would be a far smarter move. The Leak sounds lovely, has surprising grip and can hold its own against some pretty serious amps and it works well with a cheap passive pre-amp.

I heard a Leak Stereo 20 just the once and it was absolutely lovely...

[Ninanina]

The Meishu is a lovely sounding beast. So you rate it as warmer sounding than the Oto SE?

s.

I did not list the amps in order of 'warmness' but I guess yes the Meishu is slightly warmer than the Oto

[plastic penguin]

I agree with that last post - my Cary's certainly aren't warm and fuzzy and dont lack bass slam. For me there there's a musicality and purity with SE that SS just can't match. But the cons... All the above is dependent on design and valves used. But the biggest headache is the cost of retubing the things which can be ludicrously expensive if going the ELROG et al route. As someone said, you pays your money....

Adey

In perpetual pursuit.

How do you define "fuzzy"? Are you talking about harmonic distortion or something else? And does it have to be warm to be fuzzy? Perhaps I'm looking too deep into your phrasing....

I was half tempted, a few years ago, by Graaf valve amp but the fact the review said they got very warm after a relatively short playing time (and possible valve damage) put me off the notion.

[Ninanina]

How do you define "fuzzy"? Are you talking about harmonic distortion or something else? And does it have to be warm to be fuzzy? Perhaps I'm looking too deep into your phrasing....

I was half tempted, a few years ago, by Graaf valve amp but the fact the review said they got very warm after a relatively short playing time (and possible valve damage) put me off the notion.

Richard I think most valve amps get physically warm and certainly my SET amps get nice and toasty but it's nothing to worry about as that's the way they are...

[walpurgis]

How do you define "fuzzy"? Are you talking about harmonic distortion or something else? And does it have to be warm to be fuzzy? Perhaps I'm looking too deep into your phrasing.....

You need to hear a valve amp clipping to picture the type of sound.

Valve quitar amps are often designed to do it deliberately.

[farflungstar]

Read fuzzy as soft. But it really does depend on the amp and valves. An excellent example of either type can be incredibly musically engaging as well as sonically good in all departments. The Cary's were originally reviewed alongside the latest Krell class A monster amp - both were rated equally as state of the art with the reviewer unable to choose between them. I agree with arkless that SS suffers a disadvantage of not being pure class A. I've owned class A SS and the difference is obvious - more liquid and a load of other adjectives normally associated with valves.


In perpetual pursuit.

[walpurgis]

I agree with arkless that SS suffers a disadvantage of not being pure class A.

Yes it is.

http://i63.tinypic.com/30xbvw1.jpg

[southall-1998]

Yes it is.

http://i63.tinypic.com/30xbvw1.jpg


The amount of times I placed my naked foot on your fuzzy Monarchy ;)

S.

[farflungstar]

I meant the majority lol. Personally if I ever returned to SS it would have to be class A.

Adey

In perpetual pursuit.

[Gazjam]

The amount of times I placed my naked foot on your fuzzy Monarchy ;)

S.

Freudian Alert, quick nurse....the Screens!

[walpurgis]

Freudian Alert, quick nurse....the Screens!

I'm afraid Shane is beyond help. :D

[southall-1998]

I'm afraid Shane is beyond help. :D


Tiz true! Coz I did it, whilst you were in the kitchen making my tea :eek:

S.

[walpurgis]

Tiz true! Coz I did it, whilst you were in the kitchen making my tea :eek:

S.

I believe it. :)

[plastic penguin]

Looked on the Cary Audio site and the SI-300.2d looks interesting. Do like the notion of a hybrid (Class A and A/B). There aren't prices listed but I can imagine they don't come cheap.

That's the issue I have with valve amps. Unless you go s/hand, they tend to be out of a lot of peoples budget -- including mine. But s/hand has its pitfalls...

More than happy with my current bundles: They do everything I need from a music set-up and some...

By the same token, it's always good to see whether the grass really is greener.

[farflungstar]

I got my 805c's second hand (still not cheap). Personally I wouldn't buy from Cary I'd buy from the original designer/builder of the 805's Dennis Had who is retired. He hand builds some cracking little amps in his retirement and sells them (about 6 a year) on eBay. They come in at around £900 but are very highly regarded stateside. User radioman731 - he also creates some lovely preamps. Most of the time he has nothing for sale so you need to keep checking as gear goes very quickly when he lists one. He's also a pleasure to deal with, a gentleman.

You could also speak to Nick Gorham of Longdog audio, and a fellow member. He can create something especially for you, within your budget and is a genius with valves. If and when I decide to upgrade he would be on my list of possible pathways to Nirvana.


Adey

In perpetual pursuit.

[nthall]

I've switched back and forth between solid state, and tubes quite a few times. I've been happy with different models of both. Class A solid state amps can throw off heat just as well as any tube amp I've ever used.

Second hand amps that are likely to hold their re-sale value are the route I would take if you're looking to try them out. You'll be able to get your money back if you don't like them.

Tube amps are absolutely dependant on the transformers the circuit was designed around. I've built the circuits with off the shelf parts, and they never compare to the originals. They might sound good, but they never sound the same. Changing the tubes in them can drastically change the tone as well. Sometimes for the better.

Solid state amps don't seem to be as picky about the transformers, but if you go cheap you'll probably hear it.

I've heard warm and fuzzy, and I'm not convinced it's better. It's different. That could be enjoyable, or annoying depending on your tastes. Every amp is going to have it's own qualities. I haven't found the perfect one for all situations yet. Searching is part of the fun for me.


Sent from my Z981 using Tapatalk

[Reffc]

Same here:) A valve amp certainly doesn't have to be lush sounding.. I've heard the odd one that sounds more "transistory" than most SS amps! In the case of SET's though they will intrinsically have around 5-10 times the distortion of a push pull amp and much of this even order (predominantly second in fact) and this will tend to give a "lush" "warm" effect to anything going through it. Also a valve amp can have superb bass but ultimately is held back here by the transformer. Not to say a valve amp with superb grip and punch cannot be as good as an average to good SS amp but ultimately the cards are all marked in favour of SS when it comes to bass;)

A bit of a generalisation there Jez don't you think?

Many valve amps have no trouble dipping as low as sub 10 Hz (not that you want that when playing vinyl) and valve amps using sufficient global negative feedback to get the output impedance down don't suffer from any lack of bass grip. The only "issue" here is whether the designer, when using negative feedback has a) used enough of it and b) implemented appropriate and competent time compensation. Some actually don't! I suspect that's why you see so many using 5 or 10dB GNF without compensation....makes you wonder if a lot of the circuit copy-cat merchants know how to implement compensation properly or at all.

The Radford STA 15 and STA25 are a point in question. They manage to deliver sub 0.18 Ohms output impedance so damping factor is superb, and there's no lack of bass or bass control. I've heard one of Anthony's Copper amps and that had no lack of control either.

[plastic penguin]

The Class A amp I have compared to my Leema was Sugden. Given it was twice the retail price of my amp wasn't impressed.

It is true the Sugden had deeper bass but the Leema counters easily by giving tauter, better defined LFs. Mind you, I've yet to hear any amp below £2500 that betters the Leema in the bass dept. (and I've heard quite a few incl. Roksan Monoblocs, entry-level Bryston...)

If and when I upgrade I think it'll be a very short list of Leema Tucana, Accuphase, Luxman and probably a hybrid valve amp of some description.

[Reffc]

Same here:) A valve amp certainly doesn't have to be lush sounding.. I've heard the odd one that sounds more "transistory" than most SS amps! In the case of SET's though they will intrinsically have around 5-10 times the distortion of a push pull amp and much of this even order (predominantly second in fact) and this will tend to give a "lush" "warm" effect to anything going through it. Also a valve amp can have superb bass but ultimately is held back here by the transformer. Not to say a valve amp with superb grip and punch cannot be as good as an average to good SS amp but ultimately the cards are all marked in favour of SS when it comes to bass;)

A bit of a generalisation there Jez don't you think?

Many valve amps have no trouble dipping as low as sub 10 Hz (not that you want that when playing vinyl) and valve amps using sufficient global negative feedback to get the output impedance down don't suffer from any lack of bass grip. The only "issue" here is whether the designer, when using negative feedback has a) used enough of it and b) implemented appropriate and competent time compensation. Some actually don't! I suspect that's why you see so many using 5 or 10dB GNF without compensation....makes you wonder if a lot of the circuit copy-cat merchants know how to implement compensation properly or at all.

The Radford STA 15 and STA25 are a point in question. They manage to deliver sub 0.18 Ohms output impedance so damping factor is superb (ok it's not sub 0.05 Ohms but that's almost irrelevant given most passive crossover losses), and there's no lack of bass or bass control. I've heard one of Anthony's Copper amps and that had no lack of control either, nor did one of Nick's when I listened in on a room that he was exhibiting in.

Perhaps it's more accurate to say that poorly engineered valve amps have little bass grip, and even more accurate to suggest that this only applied to valve amps that aren't primarily intended to drive high efficiency horns, or indeed driving high efficiency horns where SE makes a lot of sense.

Some SE amps can have remarkably low distortion through much of their bandwidth as the signal level is reduced (so are low in distortion) typically having assymetric transfer characteristics, so that any distortion encountered when over driven tends to be even order. PP designs tend to cancel out much of the even order harmonic distortion as they run back to back, having symmetric transfer characteristics. If over-driven they can sound harsher than SE equivalents as a result. It's true to say that used WITHIN their efficient operating bands, a well engineered SE valve amp is LOW in distortion, which blows any myth about all SE's having high distortion out of the water. Horses for courses really. You don't pick an SE amp to drive inefficient 'speaker designs or those with high back EMF and large cone inertia/poor damping.

I've heard countless systems using AN amps to drive inefficient speakers and in every case, the sound has been obviously high in distortion and low in fidelity, a point in case.

A final thought is that few valve amp makers pay sufficient attention to S/N. TRON is one that does (in fact, it's one of their specialities, engineering very high S/N ratios so that when used with high efficiency speakers, the "inky blacks" remain "inky black"!). This is important where driving anything much more sensitive than 94 or 95 dB/1w/1m.

[Zoidburg]

I've not had loads and loads of amps but have spend the last few years with a consonance valve amp as my main amp. It's only recently I've developed itchy ears and started using a big SS amp. They do sound very different with the SS having more weight and heft about it. That's not to say I don't love what the consonance does because I do, it's hugely musical in its own right and I can listen to it for hours as it just sounds lovely.

[macvisual]

I'm presently going through a headache at the minute trying to decide on a power amplifier (or mono-blocks) for my current hi-fi system.
I recently picked up a Tube Technology Unisis and when it arrived it was faulty and sent it back, bad luck stuff, so looking around a lot now. There's a Job 225 (Goldmund) stereo power amplifier I've seen for sale recently but don't know much about this, although seems to receive good reviews etc....

So on the lookout for something now either valve or SS, too much choice out there in amplifier land!

Regards;
Peter
Central Scotland

[Joe]

For me the main 'con' of valve amps is the faff/expense of changing and re-biasing valves, with the associated audio nervosa that goes with wondering whether the valves need changing or not. I now have two SS systems and am happy with both, though I sometimes recall with fondness the Border Patrol power amp I had for 10 years or so.

[spendorman]

A bit of a generalisation there Jez don't you think?

Many valve amps have no trouble dipping as low as sub 10 Hz (not that you want that when playing vinyl) and valve amps using sufficient global negative feedback to get the output impedance down don't suffer from any lack of bass grip. The only "issue" here is whether the designer, when using negative feedback has a) used enough of it and b) implemented appropriate and competent time compensation. Some actually don't! I suspect that's why you see so many using 5 or 10dB GNF without compensation....makes you wonder if a lot of the circuit copy-cat merchants know how to implement compensation properly or at all.

The Radford STA 15 and STA25 are a point in question. They manage to deliver sub 0.18 Ohms output impedance so damping factor is superb, and there's no lack of bass or bass control. I've heard one of Anthony's Copper amps and that had no lack of control either.

Had a Radford STA25 III for over than 40 years (frightening, just worked it out), superb amp, Lots of other amps here too, but this is my favourite stereo amp. I am excluding a Rogers made Williamson as it's mono.

[hifi_dave]

You could get the best of both worlds with a Croft.

[plastic penguin]

You could get the best of both worlds with a Croft.

That's make I had in mind. I believe you get the best of both worlds (theorizing); the tautness and speed of a good quality SS and the texture of valves.

[Arkless Electronics]

I've switched back and forth between solid state, and tubes quite a few times. I've been happy with different models of both. Class A solid state amps can throw off heat just as well as any tube amp I've ever used.

Second hand amps that are likely to hold their re-sale value are the route I would take if you're looking to try them out. You'll be able to get your money back if you don't like them.

Tube amps are absolutely dependant on the transformers the circuit was designed around. I've built the circuits with off the shelf parts, and they never compare to the originals. They might sound good, but they never sound the same. Changing the tubes in them can drastically change the tone as well. Sometimes for the better.

Solid state amps don't seem to be as picky about the transformers, but if you go cheap you'll probably hear it.

I've heard warm and fuzzy, and I'm not convinced it's better. It's different. That could be enjoyable, or annoying depending on your tastes. Every amp is going to have it's own qualities. I haven't found the perfect one for all situations yet. Searching is part of the fun for me.


Sent from my Z981 using Tapatalk

Erm... what transformers? Other than a very few exceptions such as a Quad 50E SS amps don't have output transformers;)

[Haselsh1]

The only valve amp I have heard that could be described as lush was an Audion Sterling ETSE which used EL34's and had a midrange to die for. Only 12Wpc but the most beautiful midrange I have ever heard including my current Prima Luna combo. I used it with Audio Note AZ-2's.

[Jimbo]

That's make I had in mind. I believe you get the best of both worlds (theorizing); the tautness and speed of a good quality SS and the texture of valves.

I use the Croft 7 which is the best of both worlds being an OTL amp as well no problems with nasty transformer noise. The input valve and MOSFETS coupled with an OTL design work very well in my system. Not sure the MOSFETS sound like valves but I believe they perform in a similar way.
Very transparent sounding and marvellous with vocals and acoustic instruments.

[Firebottle]

Not sure the MOSFETS sound like valves but I believe they perform in a similar way.

The MOSFETS do indeed operate in a very similar way to a vacuum tube but the real benefit is that they are a low impedance device (as opposed to valves being quite high impedance devices), hence the ability to drive speakers directly.

When a MOSFET is used in a power 'buffer' mode, i. e. without providing any gain, it has virtually no sonic signature.
Use a valve for the gain stage(s) and you do have the best of both worlds, IMHO.

:)

[Arkless Electronics]

A bit of a generalisation there Jez don't you think?

Many valve amps have no trouble dipping as low as sub 10 Hz (not that you want that when playing vinyl) and valve amps using sufficient global negative feedback to get the output impedance down don't suffer from any lack of bass grip. The only "issue" here is whether the designer, when using negative feedback has a) used enough of it and b) implemented appropriate and competent time compensation. Some actually don't! I suspect that's why you see so many using 5 or 10dB GNF without compensation....makes you wonder if a lot of the circuit copy-cat merchants know how to implement compensation properly or at all.

The Radford STA 15 and STA25 are a point in question. They manage to deliver sub 0.18 Ohms output impedance so damping factor is superb (ok it's not sub 0.05 Ohms but that's almost irrelevant given most passive crossover losses), and there's no lack of bass or bass control. I've heard one of Anthony's Copper amps and that had no lack of control either, nor did one of Nick's when I listened in on a room that he was exhibiting in.

Perhaps it's more accurate to say that poorly engineered valve amps have little bass grip, and even more accurate to suggest that this only applied to valve amps that aren't primarily intended to drive high efficiency horns, or indeed driving high efficiency horns where SE makes a lot of sense.

Some SE amps can have remarkably low distortion through much of their bandwidth as the signal level is reduced (so are low in distortion) typically having assymetric transfer characteristics, so that any distortion encountered when over driven tends to be even order. PP designs tend to cancel out much of the even order harmonic distortion as they run back to back, having symmetric transfer characteristics. If over-driven they can sound harsher than SE equivalents as a result. It's true to say that used WITHIN their efficient operating bands, a well engineered SE valve amp is LOW in distortion, which blows any myth about all SE's having high distortion out of the water. Horses for courses really. You don't pick an SE amp to drive inefficient 'speaker designs or those with high back EMF and large cone inertia/poor damping.

I've heard countless systems using AN amps to drive inefficient speakers and in every case, the sound has been obviously high in distortion and low in fidelity, a point in case.

A final thought is that few valve amp makers pay sufficient attention to S/N. TRON is one that does (in fact, it's one of their specialities, engineering very high S/N ratios so that when used with high efficiency speakers, the "inky blacks" remain "inky black"!). This is important where driving anything much more sensitive than 94 or 95 dB/1w/1m.

Absolutely not!!!

SS amps have a huge advantage over valve amps in the bass and this is 100% measurable and repeatable. If you read my previous post again you will see that I said valve amps can have very good grip and punch in the bass... However it will never technically come any where near a good SS design. SS amps can be an order of magnitude better here!! And you are trying to "cheat" by using a Radford as the example :) Radford valve amps are technically pretty much the best ever made, yes even after all these years. They are hardly typical!

Power bandwidth (not small signal bandwidth) for a valve amp (in all discussion here I am referring to power amps BTW) is lousy. A typical 100W valve amp will deliver only around 10-20W at 20Hz! And that will usually be for several % distortion.

Direct coupled SS amps (most are) can easily be designed to give full power down to DC! Most are deliberately rolled of at a few Hz to avoid amplifying offset voltages from a preceding pre amp but typically a SS amp will deliver full output even at 5Hz and with no increase in distortion whatsoever. Crown DC300A is an example of a SS amp which is allowed to go down flat to DC.

Output impedance. For a typical valve amp using NFB (negative feedback) about 0.6R. For a typical SS amp about 0.05R or less.

It's completely game, set and match to SS at the bottom end! This doesn't mean of course that a valve amp can't be sufficiently good in the bass to subjectively seem impressive. They can. Really analyse it though, get the power up and the frequency going down, and it's no contest. SS wins and by a huge margin of x10 or more.

The reasons for all this and many other typical shortcomings with valves is not, per se, the valves themselves. It is firstly the presence of an output transformer and secondly (much less important and can be got round, sometimes, with difficulty) the fact that valve only come in "NPN". For the non technical what I mean here is that transistors are readily available in "mirror image" polarities NPN and PNP. Valves are not. Ask any audio electronic engineer what he would give his eye tooth for and most will say "PNP valves!"... including me!

Radford valve amps measure so good because that's what they were designed to do. No way in a million years were they in any way designed by ear.
Their superiority comes from the fact that everything about them was optimised to allow as much NFB as possible to be applied... exactly the opposite of what many audiophiles today want!:lol:
The huge (for a valve amp) 36dB of NFB used in some Radfords was enabled by two things:

1/ Truly superb output transformers designed by Arthur Radford.

2/ A wide bandwidth triode/pentode long tailed pair phase splitter designed by Arthur Bailey (who later became well known for "inventing" the transmission line speaker... yes , yes that's way it's in "")

Both of these things minimise phase shift and hence allow more NFB to be applied before instability.

Life's too short for me to attempt to explain Nyquist Stability Criteria to lay folks but take it as read that you can only apply so much NFB to an amp before it goes unstable. The phase compensation Paul mentions is part of maximising the NFB and allaying the point of instability. There is no such thing as time compensation in an amp BTW. Also applying only 5-10 dB of feedback would usually not need any compensation and is a very bad idea anyway as such small amounts of NFB can actually make things worse and result in much higher odd order distortion... all for reasons technically well beyond the scope of a post on AOS. For those with enough interest look up works by Scroggie, Baxandall, Atwood and Terman.

Single ended amps are intrinsically much higher in distortion than push pull amps due to the asymmetrical transfer characteristics they possess.
This applies to ALL amplifiers no matter whether valve, SS, whatever... Again life's too short for all the caveats so assume the push pull amp is class A to ensure we are comparing apples with apples. ALL single ended amps are class A. They wouldn't work otherwise! (as there will no doubt be a clever twat yes they can work in class C and E but this is only applicable to radio frequency amplifiers ie driving an aerial on the end of a transmitter:ner:)

If we take a small enough section of a curve it can be taken as being a straight line, even in the case of the asymmetrical curve of a SE amp. This is why small signal amplifiers (for this context pre amps phono stages etc) are very often SE and yet still manage very low distortion and work great.
Take an SET, let's say it is quite a powerful one at 20WPC. It's saving grace can be that its distortion V power will follow a monotonic function and so IF we are only using 1W with suitably 103dB/W type efficient speakers then the distortion at this low power level can be only 0.1% and so all tickety boo etc. This often of course exactly how they are used in practice and hence with the right speakers you can get away with it. Take the same amp and increase the output to 10W and distortion will no doubt be in the 5% region and completely unacceptable. Increase it to 18W, just a couple below its maximum rating, and you'll probably see something like 10%+ distortion. 10% is the maximum considered acceptable for "Tannoy systems" in railway stations etc as any more and the intelligibility of speech suffers!

Take the same big triodes and power supply and make them into a push pull amp, still using zero feedback, and not only will power go up but with good design it is possible to get no more than 1% distortion at 20W. A few commercial valve amps, some Audion,s come to mind but there are others, take this approach and it is vastly technically superior to using the same valves in an SET amp!!

I just wish I understood fuses and lengths of 3 core mains flex as well.... :ner:

[farflungstar]

My Cary's have NFB that can be switched off completely or applied gradually. The sound is so much better without NFB it's a no brainer. Bass gains a little better 'clarify' but highs are f*cked, strangled, mangled compared to zero applied. This may be poor design (Dennis Had reputedly said he only included the function so people could hear how bad feedback was so maybe didn't use best practice lol).

Adey

In perpetual pursuit.

[Arkless Electronics]

You could get the best of both worlds with a Croft.

I vehemently disagree but for political (with a small p) reasons all I'll say is, to misquote Crocodile Dundee "call that a hybrid power amp? THIS is a hybrid power amp" http://theartofsound.net/forum/showthread.php?41370-New-products-in-the-pipeline

The main boards were also completed and tested (I didn't add photos) and in fact so much was completed that I could actually finish this in a day or so if I put my mind to it.... "why did you abandon it after spending about 5 weeks working on virtually nothing else Jez?" I hear you say... Because it would be very expensive, probably £4K + even bought from me, and so no dealer margin, and I suddenly thought to myself "Jez, You're only really doing this as technical tour de force.. to show off really... you've got more chance of shagging Rachel Riley then ever selling one so get the fuck back to doing stuff to pay the rent" :D:eek::eyebrows:

It was completed and tested to the point where I know it will work ie one channel going (both are built) with the housekeeping circuitry on a breadboard and a bench power supply in temporary use for testing...

Edit. I never listened to it even in mono form as it was, in this test form, too big, unwieldy and fragile to move from the work bench...

[Arkless Electronics]

I use the Croft 7 which is the best of both worlds being an OTL amp as well no problems with nasty transformer noise. The input valve and MOSFETS coupled with an OTL design work very well in my system. Not sure the MOSFETS sound like valves but I believe they perform in a similar way.
Very transparent sounding and marvellous with vocals and acoustic instruments.

To follow on from what Alan said it should be borne in mind that they are far more like pentode valves than triodes ;) Comparisons with valves though only hold good to a certain extent... many aspects are most un valve like and in many ways more similar to a bipolar transistor (that's a "normal" transistor to you lot;))

Mosfets are my usual weapon of choice for power amps though.... but not always ;)

[Arkless Electronics]

My Cary's have NFB that can be switched off completely or applied gradually. The sound is so much better without NFB it's a no brainer. Bass gains a little better 'clarify' but highs are f*cked, strangled, mangled compared to zero applied. This may be poor design (Dennis Had reputedly said he only included the function so people could hear how bad feedback was so maybe didn't use best practice lol).

Adey

In perpetual pursuit.

See my remarks above about small amounts of NFB. For the technically minded I commend this excellent paper by Bruno Putzeys http://www.edn.com/design/consumer/4418798/Negative-feedback-in-audio-amplifiers--Why-there-is-no-such-thing-as-too-much

There are superb amps with loads of feedback out there just as there are with little or non BTW. So many ifs, buts and caveats come into it that it is not possible to say that NFB is a bad thing. See also "do all apples have pips" by Reeves and Mortimer :D

[Arkless Electronics]

Bet that lots killed the thread :D Unlike if it was on mumbo jumbo about magic beans in which case it would go on for 30 pages...:sofa:

[farflungstar]

I don't think it will have killed the thread - FB is an important topic. Though I take your point about 30 page topics on magic beans.. but magic does exist... It's just unprovable hence its called magic.
Adey

In perpetual pursuit.

[Macca]

Vic says:

'I can tell you if an orange has got pips just by looking at it. I discovered this at the age of five and thought I’d got it made. Unfortunately, it’s not a marketable skill as such. These days they mark up oranges as seeded or seedless, so any fool can do it. '

[walpurgis]

Bet that lots killed the thread :D Unlike if it was on mumbo jumbo about magic beans in which case it would go on for 30 pages...:sofa:

Just start a thread on cable directionality Jez. That'll keep 'em going for a week or two. :D

[Haselsh1]

I use the Croft 7 which is the best of both worlds being an OTL amp as well no problems with nasty transformer noise. The input valve and MOSFETS coupled with an OTL design work very well in my system. Not sure the MOSFETS sound like valves but I believe they perform in a similar way.
Very transparent sounding and marvellous with vocals and acoustic instruments.

The only thing I have against Croft is the cheap, nasty tin box brigade that it is tied to. Compared to most production units Croft units will be really nice when they're finished. For me though, it looks like a badly built kit. Sound quality wise, stunning. The level of detail is truly amazing.

[Ninanina]

Do like the notion of a hybrid

Richard I have owned 2 very well respected hybrid amps, the Unison Research Unico and a Copland CSA28 but found both of them lacking in their sound quality... they are neither as punchy and bass heavy as a ss amp and not as involving, or have the character, of a good valve amp so I would not recommend a hybrid...

However, again, it might be that there are hybrid amps that sound better than the ones I owned

[Arkless Electronics]

The only thing I have against Croft is the cheap, nasty tin box brigade that it is tied to. Compared to most production units Croft units will be really nice when they're finished. For me though, it looks like a badly built kit. Sound quality wise, stunning. The level of detail is truly amazing.

If it was in a fab looking box and had better controls with better "feel" to them it would cost literally twice as much... but sound the same... Just saying :)

[Arkless Electronics]

Richard I have owned 2 very well respected hybrid amps, the Unison Research Unico and a Copland CSA28 but found both of them lacking in their sound quality... they are neither as punchy and bass heavy as a ss amp and not as involving, or have the character, of a good valve amp so I would not recommend a hybrid...

However, again, it might be that there are hybrid amps that sound better than the ones I owned

The precise way it's implemented is infinitely more important than whether it's valve, SS or hybrid ;)

All presently commercially available hybrid power amps I am aware of are far too crudely designed and to the extent that they offer "the worst of both worlds" to quite an extent. Just the power supply for the one I designed, and linked to earlier, is about 4 x as complicated as a whole Croft hybrid power amp for example... and to make it commercially viable the protection circuitry alone would be around 10 x as complicated. I didn't get round to the protection circuitry as, for my own use and to verify the idea, I would trust the freshly made and adjusted unit, checked daily for issues, to work safely and reliably enough. The protection circuitry would have no effect on the sound BYW so could be left for the time being... that was the plan. Obviously it would have to be incorporated before a potential customer was even loaned a demo unit for a couple of days!!

Did you once own a Hi Fi shop Bev? Bishop Stortford (or something sounding similar) being the location comes to mind but may be false memory!

[Jimbo]

If it was in a fab looking box and had better controls with better "feel" to them it would cost literally twice as much... but sound the same... Just saying :)

Absolutely right Jez and that's the point of Croft. Great sound and not bling boxes . However I like the utilitarian look Croft uses for his amps. I am sure there is stuff out there where the box is the most expensive part of the kit and the only bit work paying for :lol:

[Jimbo]

The MOSFETS do indeed operate in a very similar way to a vacuum tube but the real benefit is that they are a low impedance device (as opposed to valves being quite high impedance devices), hence the ability to drive speakers directly.

When a MOSFET is used in a power 'buffer' mode, i. e. without providing any gain, it has virtually no sonic signature.
Use a valve for the gain stage(s) and you do have the best of both worlds, IMHO.

:)

Cheers for the technical appreciation Alan.:thumbsup:

[Ninanina]

they offer "the worst of both worlds"

Did you once own a Hi Fi shop Bev? Bishop Stortford (or something sounding similar) being the location comes to mind but may be false memory!

Jez "the worst of both worlds" is exactly how I would describe the two hybrid's I owned

Err no I have never owned a hifi shop, although I have probably owned enough hifi over the years to fill one :doh:

[Gazjam]

Theres nowt much wrong with a hybrid valve amp... ;)
Like amps of any type I guess, all in the design and implementation.

[plastic penguin]

Richard I have owned 2 very well respected hybrid amps, the Unison Research Unico and a Copland CSA28 but found both of them lacking in their sound quality... they are neither as punchy and bass heavy as a ss amp and not as involving, or have the character, of a good valve amp so I would not recommend a hybrid...

However, again, it might be that there are hybrid amps that sound better than the ones I owned

I like the priciple of a hybrid amps. I've not heard any, but as a SS owner, they are hard to fault, especially in isolation.

[plastic penguin]

Theres nowt much wrong with a hybrid valve amp... ;)
Like amps of any type I guess, all in the design and implementation.
Concur. We also need to keep it perspective and understand that valves and SS have their own distinct sonic flavour.

[Haselsh1]

Currently I have both on tap as I kept my big output SS amp even though I upgraded to the Prima Luna pre/power combo. There are times when I just want the sheer grip that a good SS amp has, especially one with a shedload of Watts that offers such effortless bass. OK, it is nowhere near the valves in terms of clarity and fluidity but it has its own place in the grand scheme of things.

[jandl100]

A valve amp and SS amp, if both are competently designed and rated for the speakers being driven should sound pretty similar.

That's certainly my experience.

There is not a valve sound or a solid state sound. You can get a huge variety of presentations from both camps, and they substantially overlap.

Given the extra expense of valve amps (e.g. large output transformers if you want serious grip on difficult speaker loads) I honestly don't think they justify the cost in terms of sonic achievement.
They can look seriously nice, though! :)

Well designed (not necessarily expensive) solid state amplification is all anyone really needs in terms of sound quality, imho.

I do love my valve pre-amp, though. It just looks so cool with its exposed valves glowing. :eek:

[Yomanze]

Pros of using valve amps: easier to get a subjectively natural and liquid midrange / top end & good micro-dynamics.
Cons of using valve amps: harder to beat the bass of solid state, and the maintenance of tubes.

Pros of using solid state amps: easier to maintain, fit & forget, better bass and macro-dynamics.
Cons of using solid state amps: extremely difficult to get the 'grain' i.e. that 'solid state sound' down to a level that tubes achieve. Some people may prefer the balance of SET amps & who am I to argue.

[Haselsh1]

My own personal experience is that there is a huge gulf of difference between solid state and valves. Which one the OP may prefer is down to him/her to find out by auditioning.

Even with guitar amplifiers there is a massive difference between the two types.

[Reffc]

I think we'll agree to disagree on valve amps Jez. It's not game set and match at all, as that comment is completely out of context! It depends entirely on the loudspeakers being driven, the crossover design and the listening requirements/music, but a good valve amp can and will have an output impedance below 0.6 Ohms. I'll repeat that the Radfords measure just 0.18 ohms, and given many loudspeaker passive crossover losses, there's little advantage in much lower output impedances if you're losing 0.6 to 0.8 Ohms Ohms through the cable loop resistance and filter anyway. The main consumer advantage of SS amps is the power output, lower cost and efficiency. You can make a much more powerful amplifier in a much smaller case, for less and for a lot of inefficient speaker designs, yes, SS has a huge advantage. That has to be balanced though with the fact that many loudspeaker systems are only using a handful of watts for much of the program material, and its only hard to drive or very inefficient designs that need more driving at low to normal listening volumes, hence for most purposes, a good valve amp doesn't really lose out. It all depends on the loudspeaker load. Game, set and match? No, absolutely not unless you're using purely cost as a measure.

[anthonyTD]

Well, this is another of those threads that will either unite, or devide us!:)
Excelent resusts can be atained by either technology, you just have to know how to implement each topology, to get the best out of it.
My own choice for Single ended was a Hybrid design, although I chose to use the solid state devices to drive' and control the valves, rather than doing away with the output valves and transformers etc.
Anyone who has heard the Soul amps will I am sure, agree that they do not sound like typical valve amps, let alone single ended ones!
The argument of which technology is best will' I am sure rage on, until well after many of us here have shuffled off into the sunset, However, I stand by what I have said here, and many times in the past, when you partner a decently well designed Valve amp to the right speaker, you will imediately realise what it is about the technolgy that keeps them in the limelight, and why I am sure they will still be around in many systems for the foreseeable future.:)

[Spectral Morn]

Pretty much always used valve amps, tried a few hybrids and would concur with Bev re Unison Research Unico, but the Pathos Classic One mk2(must be the mk2, as mk1 isn't as good, and the mk3 has lost some of the mk2's magic) is a stunner, add another and you can have a mono integrated and 175watts, over the single amps 75 watts. There is a switch inside to turn it from stereo to mono. Loved the Pathos Twin Towers amp but the Pathos Logos was veiled and stodgy in the bass.

I would definitely put Pathos on your to hear list.

I also own a Balanced Audio Technology VK300 Se integrated hybrid, which I like a lot.

Pure valve amplifiers have a finesse and delicacy, air and sound-staging ability that few solid state amplifiers can manage, outside of lower powered Class A designs. Only solid state I have ever desired to own are of that type.

Matching of speakers to amplifiers is required for all situations, yes valve amplifiers often need closer matching, but assuming more solid state power guarantees an easy option isn't the case in my experience. To assume that could land you in trouble regarding bass control, extension and tonality. All parts of an audio system need to be matched, and listening and trying are the only ways to find a synergistic match.

[Arkless Electronics]

I think we'll agree to disagree on valve amps Jez. It's not game set and match at all, as that comment is completely out of context! It depends entirely on the loudspeakers being driven, the crossover design and the listening requirements/music, but a good valve amp can and will have an output impedance below 0.6 Ohms. I'll repeat that the Radfords measure just 0.18 ohms, and given many loudspeaker passive crossover losses, there's little advantage in much lower output impedances if you're losing 0.6 to 0.8 Ohms Ohms through the cable loop resistance and filter anyway. The main consumer advantage of SS amps is the power output, lower cost and efficiency. You can make a much more powerful amplifier in a much smaller case, for less and for a lot of inefficient speaker designs, yes, SS has a huge advantage. That has to be balanced though with the fact that many loudspeaker systems are only using a handful of watts for much of the program material, and its only hard to drive or very inefficient designs that need more driving at low to normal listening volumes, hence for most purposes, a good valve amp doesn't really lose out. It all depends on the loudspeaker load. Game, set and match? No, absolutely not unless you're using purely cost as a measure.

Did you read all of my reply? Including the bits about how the Radford is far ahead of most valve amps and not typical etc? I fully agree that a Radford can be as low as 0.18R output impedance and I repeat that 0.6R would be typical of a modern valve amp. It would not be difficult to find ones down to 0.3 or up to 1 or higher either, hence 0.6 as a reasonable typical figure. I'm afraid you are simply technically wrong on this. At the bass end it is very definitely game set and match and no contest to SS amps as I will prove in measurements to anyone who wishes to bring both types to my workbench. It is very basic established fact. That is technical and not subjective of course.

To clarify, I am not for one second saying that valve amps can not do bass or always lack grip or anything of the sort subjectively.

Non of what I say has anything to do with speakers which you are bringing in to it. For all the reasons you mention it is indeed debatable as to whether it's necessary to have output impedance below say 0.2 - 0.4R. However the fact is that SS amps routinely better this by a factor of ten and that valve amps struggle to even manage it.

[Arkless Electronics]

Jez "the worst of both worlds" is exactly how I would describe the two hybrid's I owned

Err no I have never owned a hifi shop, although I have probably owned enough hifi over the years to fill one :doh:

Ah well there was a hi fi shop of some renown owned and run by a women called Bev in the '80's.... was putting 2 and 2 together;)

[dimkasta]

I' ve had/have various high-endish amps both SS and tube.

Saying that valves are better than ss or the other way around is like saying that blondes are better than brunettes. Everyone will have an opinion, but it all depends on many other things as well.

Where tubes have a distinct advantage is when we are talking for triodes. Mainstream SS devices simply cannot offer that kind of linearity. Maybe perhaps some power Jfets or older Vfets but I do not know manufacturers using those on current amps (perhaps only First Watt?). And again, we have to take into consideration the design. PP? SET? Everything will sound different.

When we are talking pentode/mosfet/transistor, things are rather on similar fields, with component selection and design playing a very big role.
Tubes will require good transformers, but SS will require good capacitors and/or good servo design.

Oh and the most important, with tubes you will need new ones every once in a while along with a good rebiasing, which will not be cheap for a high-endish amp.

What I personally prefer? I would have to say SS because I do not have to worry about ~1K in maintenance every few years. I will probably sell my 211 monoblocks soon to avoid that expense.
Will I regret it? I will have some remorse but I will not regret it :)
Will I still enjoy nice music? Absolutely.

[Arkless Electronics]

A point which IMO is almost always ignored is that if we consider a mythical perfect amplifier it will have no sound of its own and just amplify the source and drive the speakers. Everything you hear will be down to the source and the speakers. The closer real amplifiers come to perfection the more alike they will sound whether valved, SS or whatever!
By the same logic if two amplifiers sound very different to each other then at least one of them sounds wrong... maybe both!

[Marco]

At the bass end it is very definitely game set and match and no contest to SS amps as I will prove in measurements to anyone who wishes to bring both types to my workbench. It is very basic established fact. That is technical and not subjective of course.


What about a listening test instead, using any loudspeaker you care to mention that is 'valve amp-friendly', using a piece of music designed to 'catch out' the bass performance of the valve amp? The SS amp, forming part of the test, shouldn't care too much what speakers are used. Then the persons present can comment on what they're hearing :)

Technically, I'm not saying you're wrong [as I'm not qualified to do so], and I do understand and accept where you're coming from, but what you're claiming as 'indisputable fact' simply hasn't translated to my (extensive) listening experience, assessing all manner of quality SS and valve amps, providing that the speakers used were suitable and up to the task.

For example, using my Tannoy DCs as an example 'test speaker', the 50W Class A TD Copper amp I own now (using KT150 output valves), has as much tightness, grip and 'speed' in the bass as the ECS EA1 200W monoblocks I owned before it (see the stereo one here and some technical details for its design: http://www.tnt-audio.com/ampli/ea2_e.html), with EACH monoblock featuring the use of a 1500VA transformer!

Trust me, those were MASSIVE beasts, capable of driving the most difficult of loads, and very expensive, yet the Copper amp (with the Tannoys in the equation) reproduces just as convincing a rendition of a live recording of, say, a drum kit, or any kind of rock music you care to mention, as the EA2s did, otherwise I wouldn't have sold them and bought the Copper amp ;)

And the exact same has happened in my system, using the Tannoys, with a pair of Naim NAP135 monoblocks and modified Quad 405s... Furthermore, all of this was equally as evident using a pair of Spendor SP100 (very large standmounts), which I owned before the Tannoys: the Copper amp routinely showed that it was just as capable in the bass as any of the SS amps. As an aside, the Copper amp has a virtually flat frequency response from 20Hz to 100KHz.

Now I'm not saying for one second that, measurably, the claimed superiority in the bass of SS amps wouldn't be immediately obvious... *But*, for me, that means hee-haw/nowt unless it translates sonically, in a very obvious way into the listening experience, when using music, rather than measurement apparatus as the arbiter. And in my experience to date, out with of when mediocre valve amps are used in such tests, that simply hasn't happened.

Marco.

[RothwellAudio]

Even with guitar amplifiers there is a massive difference between the two types.
I wouldn't say "even with guitar amps...", I'd say that the gulf between the two types is enormous with guitar amps. Ok, guitar amps aren't even trying to be "hi-fi", but valve guitar amps are so far ahead of tranny guitar amps that it's extremely rare to see a tranny guitar amp except for budget models. The notable exception is the Roland Jazz Chorus.
Sorry for the digression - there's probably nothing about guitar amps that applies to hi-fi.

[dimkasta]

A point which IMO is almost always ignored is that if we consider a mythical perfect amplifier it will have no sound of its own and just amplify the source and drive the speakers. Everything you hear will be down to the source and the speakers. The closer real amplifiers come to perfection the more alike they will sound whether valved, SS or whatever!
By the same logic if two amplifiers sound very different to each other then at least one of them sounds wrong... maybe both!

It is ignored because every single element (including our room and our ears) imposes its own "wrongness".

And unfortunately there is no way to measure absolute "correctness" or claim that it will be perceived equally by everyone on every room.

We can only measure a few areas where one might be less wrong. But less wrong areas does not necessarily mean good.
We only have a few spotlights that are very often abused by marketing.

[dimkasta]

I wouldn't say "even with guitar amps...", I'd say that the gulf between the two types is enormous with guitar amps. Ok, guitar amps aren't even trying to be "hi-fi", but valve guitar amps are so far ahead of tranny guitar amps that it's extremely rare to see a tranny guitar amp except for budget models. The notable exception is the Roland Jazz Chorus.
Sorry for the digression - there's probably nothing about guitar amps that applies to hi-fi.

True. Guitar amps aim for tone. Not fidelity.

[Arkless Electronics]

What about a listening test instead, using any loudspeaker you care to mention that is 'valve amp-friendly', using a piece of music designed to 'catch out' the bass performance of the valve amp? The SS amp, forming part of the test, shouldn't care what speakers are used. Then the persons present can comment on what they're hearing :)

Technically, I'm not saying you're wrong [as I'm not qualified to do so], and I do understand where you're coming from, but what you're claiming as 'indisputable fact' simply hasn't translated to my (extensive) listening experience, assessing all manner of quality SS and valve amps.

For example, using my Tannoy DCs as an example 'test speaker', the 50W Class A TD Copper amp I own now (using KT150s), has as much tightness, grip and 'speed' in the bass as the ECS EA1 200W monoblocks I owned before it (see the stereo one here and some technical details of its design: http://www.tnt-audio.com/ampli/ea2_e.html), with EACH monoblock featuring the use of a 1500VA transformer!

Trust me, those were MASSIVE beasts, capable of driving the most difficult of loads, and very expensive, yet the Copper amp reproduces just as convincing a rendition of a live recording of, say, a drum kit, or any kind of rock music you care to mention, as the EA2s did, otherwise I wouldn't have sold them and bought the Copper amp ;)

And the exact same has happened in my system, using the Tannoys, with a pair of Naim NAP135 monoblocks and modified Quad 405s... Furthermore, all of this was equally as evident using a pair of Spendor SP100 (very large standmounts), which I owned before the Tannoys: the Copper amp routinely showed that it was just as capable in the bass as any of the SS amps.

Now I'm not saying for one second that, measurably, the claimed superiority in the bass of SS amps wouldn't be immediately obvious... *But*, for me, that means hee-haw unless it translates sonically, in a very obvious way into a listening experience, when using music, rather than measurement apparatus, as the arbiter. And in my experience to date, out with of when mediocre valve amps are used in such tests, that simply hasn't happened.

Marco.

As I was careful to point out in the things I said earlier in the thread, a really good valve amp can be good enough technically in the bass end that its limitations will not spoil the sound subjectively. No argument there. However, get the volume going up on material with very low bass and speakers that can reproduce it, and especially if the speakers are an awkward load, and a good SS amp will soon show its superiority here.

As I said near the beginning of the long technical post I made it is quite typical for even a good valve amp of 100WPC to be capable of only 10-20W or so down at 20 Hz and probably with 5%+ distortion. A few exceptional valve amps of 100WPC may manage 30-40W at 20Hz but that would be very unusual and takes humongous output transformers to manage it. They usually get away with it subjectively because there is not much below 40 Hz or so going on in most music and our ears are not particularly sensitive to distortion at very low frequencies.

My Jez modified Leak Stereo 20 is still only about 11WPC and yet manages to drive my KEF Reference 105.3's to impressive volumes with bass you can feel and grip/tightness that most would find more than adequate ;)

Outside of power amplifiers, with their output transformers getting in the way, there is no technical reason for valves to have any less grip or precision than SS, so, in phono stages, pre amps etc SS has no theoretical advantage over valves.

[Arkless Electronics]

I wouldn't say "even with guitar amps...", I'd say that the gulf between the two types is enormous with guitar amps. Ok, guitar amps aren't even trying to be "hi-fi", but valve guitar amps are so far ahead of tranny guitar amps that it's extremely rare to see a tranny guitar amp except for budget models. The notable exception is the Roland Jazz Chorus.
Sorry for the digression - there's probably nothing about guitar amps that applies to hi-fi.

+1 They are specifically intended to produce loads of distortion and colouration

[Spectral Morn]

Tim De P built two amps one with valve, one solid state to prove the point and I think managed to do so re them being similar. Never heard them but that only goes for those solutions so can't apply to all solid state or valve designs.

Each brings something to the party, but the power limitations on most single ended designs meant I never went down that road, though 845 single ended amps sound very nice and give reasonable power output, so speaker choice is broader.

My valve amp of choice is the Music Reference RM200 mk1

[Gazjam]

Had both types of amplification in my own system over the years, heard other amps in others systems both cheap and eye wateringly expensive, and its fair to say theres contradictions in both technologies?

SS amps that have liquid midrange, valve amps with prodigious grip and bass...
All depending on design, implementation, design and (unfortunately sometimes) cost.
I think its easier to find "good enough for a pub discussion" levels of clear distinction at the mainstream level, but gets a bit more cloudy with higher end kit?
Great examples of both types of amps, but I think "signature sounds" of the two amp technologies are less apparent at the higher end.

Eventually, we hear enough kit and discover the sound that works for us and drift towards that?

For myself I'll not go back to SS amps.
Had a couple of valve amps now, KT88 push pull and now a hybrid 300B SET.

With good valve amps, I think the price of admission can be a bit sorer than SS as your basically listening to the power supply and regulation, never mind the output transformers and valves...and these things can mount up.
Not to mention the increased need for getting the speakers right, especially for SET.

All that said, I've really enjoyed the SS budget amps I've had in the past...just a different way of presenting the music which really is what it's all about..

All part of the journey. :)

[Marco]

As I was careful to point out in the things I said earlier in the thread, a really good valve amp can be good enough technically in the bass end that its limitations will not spoil the sound subjectively. No argument there. However, get the volume going up on material with very low bass and speakers that can reproduce it, and especially if the speakers are an awkward load, and a good SS amp will soon show its superiority here.


Well, all I can say is that, awkward load aside, despite trying many times over the course of the last 10 years or so since I've got into valve amps, I've *yet* to hear that, and trust me I've had some serious SPLs going on in my listening room, and others I've tried it in, with both high-quality SS and valve amps...

Maybe one day I'll pop up to your place with the Copper amp and you can demonstrate where you're coming from, in the form of a listening test, with some appropriate music? As ever, as they say, I'm 'all ears' and keen to learn! :)

Marco.

[Marco]

A few exceptional valve amps of 100WPC may manage 30-40W at 20Hz but that would be very unusual and takes humongous output transformers to manage it.

Interesting... Anthony, what are the relevant specs here, in relation to the Copper amp? I may be wrong (as we were chatting away at the time and I wasn't paying full attention), but I'm sure the last time I was down, when you were measuring my amp, it was producing something close to the bit in bold above, as quoted by Jez :)

Marco.

[Gazjam]

"Brown note" depth of bass here, tight tuneful and thudding you in the chest.
Volume control between 8 and 9 o'clock depending on the music, any louder and the acoustic guitar on the back wall starts vibrating along...which is offputting!

Pushed it to 12 o'clock once on some chamber music and the thing just kept accellerating, no loss of control at the low end.

All from only 8watts a side triode valve amp in a medium sized room.
Contradictions in every amp type...

[Marco]

Yup, same here, mate. However, we do own exceptional examples of valve amps, designed by folk who *really* know what they're doing and how to get the absolute most from that topology! :)

What you're describing is, IMO, also to do with why folk often claim that 'valve watts' are seemingly more 'powerful' than SS watts, which is often why a well-designed, low-powered valve amp can sound subjectively bigger and 'gutsier' than a (significantly) more powerful, in terms of watts, SS amp.

For me, there's definitely something in that [no proper idea why, though] as I've heard the effect MANY times. Certainly, the Copper amp goes subjectively just as loud (whilst staying in control of the music), as did my old 200W ECS monoblocks - and I'm sure your 8W SET amp does the same in comparison with, say, any 30W SS amp you've heard.

I think Anthony had a theory about it, along the lines of valves being high-voltage devices, so the power is 'always there' and available instantaneously, whereas with SS amps the delivery isn't as immediate, or something like that... Perhaps he will elucidate?

Marco.

[Haselsh1]

With regard to sheer slam and transient speed, my current valve power amp way outstrips any of my old SS amps. It does not however have that easy, effortless low frequency that some of my SS amps have had. Of course this could just be a damn fine synergy with my current loudspeakers.

[Arkless Electronics]

Well, all I can say is that, awkward load aside, despite trying many times, over the course of the last 10 years or so since I've got into valve amps, I've *yet* to hear that, and trust me I've had some serious SPLs going on in my listening room, and others I've tried it in, with both high-quality SS and valve amps...

Maybe one day I'll pop up to your place with the Copper amp and you can demonstrate where you're coming from, in the form of a listening test, with some appropriate music? As ever, as they say, I'm 'all ears' and keen to learn! :)










Marco.

I'd rather prove it with measurements. They would make it very obvious. My speakers are nearly as efficient as your Tannoys and I have a small listening room in a flat.... We'd be rendered half deaf and dealing with all the police vehicles in attendance if trying to prove it subjectively!

It is certainly technically possible to build a 100WPC valve amp that still gives full output @ 20Hz but it is hardly ever seen in practice due to the size, weight and expense of output transformers (OPT's) required. Obviously as power goes down it becomes easier and cheaper to use OPT's that can handle it. My Stereo 20 for example has OPT's that look big enough for a 40WPC amp and yet it is only rated at 10WPC. Due to this I wouldn't be surprised if it could give full output at 20Hz.

Conversely if one looks at the OPT's in a guitar amp then in some cases the ones in a 100W amp look only adequate for about 30W if used in a hi fi amp. They aren't being called upon to amplify anything much below about 100Hz and any distortion is considered part of the signature tone of that guitar amp anyway!

As an aside there would once have been valve amps made for driving "shaker tables" which are used for testing the resistance to vibration and maximum allowable G force of whatever object/product is being tested. Some of these would have produced a KW or more at 10Hz so it can certainly be done!! The OPT though would probably have been the size of a fridge and weighed 1/2 Ton or so...

[Reffc]

Well, this is another of those threads that will either unite, or devide us!:)
Excelent resusts can be atained by either technology, you just have to know how to implement each topology, to get the best out of it.
My own choice for Single ended was a Hybrid design, although I chose to use the solid state devices to drive' and control the valves, rather than doing away with the output valves and transformers etc.
Anyone who has heard the Soul amps will I am sure, agree that they do not sound like typical valve amps, let alone single ended ones!
The argument of which technology is best will' I am sure rage on, until well after many of us here have shuffled off into the sunset, However, I stand by what I have said here, and many times in the past, when you partner a decently well designed Valve amp to the right speaker, you will imediately realise what it is about the technolgy that keeps them in the limelight, and why I am sure they will still be around in many systems for the foreseeable future.:)


:)

I agree Anthony. It's about the end result, irrespective of the technology employed, but I'm with you on your conclusions.

There are good examples of various types of technology, but I know which I prefer when using sensible high efficiency loudspeakers that don't present awkward loads. The pros & cons of one tech to another barely even come into it when comparing even the bass performance, (that's more a factor with awkward loudspeaker loads) because a competently designed valve amp will manage 20Hz-20KHz +/- a sensibly low variance and without high distortion. Problem is, we've been flooded with loads of poor quality valve amps on the market since their resurgence (including plenty of expensive ones), so folks do have to search the competent designs out which demands seeking supplementary information that often some manufacturers don't provide (nor are really willing to). Having heard your Copper amp, I'm sure that comes into the "competently designed" camp :)

[Arkless Electronics]

Yup, same here, mate. However, we do own exceptional examples of valve amps, designed by folk who *really* know what they're doing and how to get the absolute most from said topology! :)

What you're describing is, IMO, also to do with why folk often claim that 'valve watts' are seemingly more 'powerful' than SS watts, which is often why a well-designed, low-powered valve amp can sound subjectively bigger and 'gutsier' than a (significantly) more powerful, in terms of watts, SS amp.

For me, there's definitely something in that [no proper idea why, though] as I've heard the effect MANY times. Certainly, the Copper amp goes subjectively just as loud (whilst staying in control of the music), as did my old 200W ECS monoblocks - and I'm sure your 8W SET amp does the same in comparison with, say, any 30W SS amp you've heard.

I think Anthony had a theory about it, along the lines of valves being high-current devices, so the power is 'always there' and available instantaneously, whereas SS amps have to 'search' for it, or something like that... Perhaps he will elucidate?

Marco.

Sorry but complete gobbledygook and wrong in every way... Valves are LOW current devices for a start and some bits are so "out there" I ain't even going to address them!
As to valve Watts seeming louder this is manly due to softer clipping and less offensive distortion when they do clip. The higher the NFB used in a valve amp then the better the measured performance (as in the Radford) but the more similar it will be to a SS amp in terms of clipping performance and subjective max loudness.

[Arkless Electronics]

:)

I agree Anthony. It's about the end result, irrespective of the technology employed, but I'm with you on your conclusions.

There are good examples of various types of technology, but I know which I prefer when using sensible high efficiency loudspeakers that don't present awkward loads. The pros & cons of one tech to another barely even come into it when comparing even the bass performance, (that's more a factor with awkward loudspeaker loads) because a competently designed valve amp will manage 20Hz-20KHz +/- a sensibly low variance and without high distortion. Problem is, we've been flooded with loads of poor quality valve amps on the market since their resurgence (including plenty of expensive ones), so folks do have to search the competent designs out which demands seeking supplementary information that often some manufacturers don't provide (nor are really willing to). Having heard your Copper amp, I'm sure that comes into the "competently designed" camp :)

Many will do 5Hz to 100KHz +/- 1dB.... if you only want half a Watt from a 100WPC amp!!! The rest I can't argue with:)

[Marco]

Sorry but complete gobbledygook and wrong in every way... Valves are LOW current devices for a start...


Yes, sorry I meant voltage, not current. I shall amend my post accordingly.


As to valve Watts seeming louder this is manly due to softer clipping and less offensive distortion when they do clip. The higher the NFB used in a valve amp then the better the measured performance (as in the Radford) but the more similar it will be to a SS amp in terms of clipping performance and subjective max loudness.

Can't dispute that, but I suspect there's also a little more to it than that. In that respect, I'll wait for Anthony to return to the discussion and put the point I raised earlier into a proper context.

Marco.

[plastic penguin]

Personally I think Valve amps, in the main, look too industrial. There are some makes like Graaf or hybrids that look decent -- and not designed by Isambard Kingdom Brunel.

I know it's very subjective, and wouldn't knock anyone for owning or looking to buy a valve amp. At this moment, I can't imagine owning a traditional valve amp. Perhaps in 10-years or so... not now.

The thread was only started because I wanted to get a wide range of views on the subject.

[Marco]

I'd rather prove it with measurements. They would make it very obvious.


I'd rather do it by listening to (appropriate) music because a) in the real world, for a music lover and hi-fi enthusiast (not an electronics engineer), that's *ALL* that matters, and b) no matter how "obvious" it would be, measurements don't always tell the FULL story!! ;)


My speakers are nearly as efficient as your Tannoys and I have a small listening room in a flat.... We'd be rendered half deaf and dealing with all the police vehicles in attendance if trying to prove it subjectively!


Lol... Ok, we'll do it at mine then sometime, or perhaps even better, at the forthcoming NEBO? You bring your amp(s) and I'll bring the Copper amp, and we'll use a suitable set of speakers. Sounds like a great idea for a demo! :)

Marco.

[Spectral Morn]

Personally I think Valve amps, in the main, look too industrial. There are some makes like Graaf or hybrids that look decent -- and not designed by Isambard Kingdom Brunel.

I know it's very subjective, and wouldn't knock anyone for owning or looking to buy a valve amp. At this moment, I can't imagine owning a traditional valve amp. Perhaps in 10-years or so... not now.

The thread was only started because I wanted to get a wide range of views on the subject.

Its glowing glass that is the draw for me too, not just the sound. Love the look of valves.

[Gazjam]

Hear you on the industrial look of some valve amps Richard, but there's some exquisite looking ones out there.

This:
https://s-media-cache-ak0.pinimg.com/736x/22/eb/7e/22eb7ee9db6098eb653b516ad7b4e555.jpg

As compared to this:
https://s-media-cache-ak0.pinimg.com/736x/80/68/14/80681479364a3c654b03242e213c99ab.jpg

[anthonyTD]

Hi Marco,
From memory, your copper amp is pretty flat from around 20hz, to 100khz at around 70% of its power output, but I would have to re-measure it again, and take some Scope screen shots as proof the next time its in for service, in the meantime, when I get chance, I will put my own copper amp on the bench, and do some measurements on that one, I know its a more powerful version, but it will have similar spec as far as power versus frequency etc.
The elephant in the room as far as bench tests are concerned is the load which is used, most tests are conducted with Dummy loads, ie; big resistors, and not a true speaker load, so again, not an accurate representation of a real world load, as in a speaker, but due to the way impedances change with frequency ie; with a speaker' it is a more consistent one as far as testing for power and frequency, accross a broad frequency range.
Interesting... Anthony, what are the relevant specs here, in relation to the Copper amp? I may be wrong (as we were chatting away at the time and I wasn't paying full attention), but I'm sure the last time I was down, when you were measuring my amp, it was producing something close to the bit in bold above, as quoted by Jez :)

Marco.

[Arkless Electronics]

Hi Marco,
From memory, your copper amp is pretty flat from around 20hz, to 100khz at around 70% of its power output, but I would have to re-measure it again, and take some Scope screen shots as proof the next time its in for service, in the meantime, when I get chance, I will put my own copper amp on the bench, and do some measurements on that one, I know its a more powerful version, but it will have similar spec as far as power versus frequency etc.
The elephant in the room as far as bench tests are concerned is the load which is used, most tests are conducted with Dummy loads, ie; big resistors, and not a true speaker load, so again, not an accurate representation of a real world load, as in a speaker, but due to the way impedances change with frequency ie; with a speaker' it is a more consistent one as far as testing for power and frequency, accross a broad frequency range.

I believe The Copper Amp is 50WPC? Even so that spec is way above average for a valve power amp:) Nice work.

At the other extreme I seem to remember a review back in the day on a Beard valve amp which was either 80 or 100WPC and on the measurement bench it could only do 8W at 20Hz!!

[anthonyTD]

:)Of course, the other aspect that is being forgotten here is the sensitivity, and maximum sound pressure level [SPL] of a given speaker.
I believe The Copper Amp is 50WPC? Even so that spec is way above average for a valve power amp:) Nice work.

At the other extreme I seem to remember a review back in the day on a Beard valve amp which was either 80 or 100WPC and on the measurement bench it could only do 8W at 20Hz!!

[Marco]

Cheers, Anthony. That's most interesting! Looking forward to seeing how your own (bigger) Copper amp measures :)

Could you have a go at this below, please? I know you mentioned something about it once to me when we were chatting, and why you thought valves appear to sound 'bigger'/more immediate than their measured power output suggests:


I think Anthony had a theory about it, along the lines of valves being high-voltage devices, so the power is 'always there' and available instantaneously, whereas with SS amps the delivery isn't as immediate, or something like that... Perhaps he will elucidate?

Experience tells me that a 30W valve amp will sound subjectively 'bigger' and more powerful than your average 30W SS amp [and it's nowt to do with soft clipping], and I'm sure you said it was something to do with valves being high-voltage devices...

Marco.

P.S Did you get my email about those NOS 6SL7s?

[anthonyTD]

Hi Marco,
I did get your email concerning the 6SL7's, and I replied.
As for why Valve amplifiers sound more powerful, watt for watt, compared to Solid State designs, there are sevral theories, and ideas that have been put forward over the years, one is as Jez comented on, the softer clipping nature of valves compared to bipolar devices etc, however; IMHO there is more to it than that, one aspect to consider when comparing the two topologies, is to do with how the gain is controled and set around solid state devices compared to the open loop, linear nature of valves. And yes, again, IMHO, the fact that valves usualy run on much higher voltage rails than SS devices definately plays a part, of course, all of this is subjective, and I would welcome all other input and thoughts on this,I think it would make for a very interesting subject, but only if the OP doesent object. :)
Cheers, Anthony. That's most interesting! :)
i
Could you have a go at this below, please? I know you mentioned something about it once to me when we were chatting, and why you thought valves appear to sound more 'powerful' than their measured power output suggests:



Experience tells me that a 30W valve amp will sound subjectively 'bigger' and more powerful than your average 30W SS amp [and it's nowt to do with soft clipping], and I'm sure you said it was something to do with valves being high-voltage devices...

Marco.

P.S Did you get my email about those NOS 6SL7s?

[Arkless Electronics]

Hi Marco,
I did get your email concerning the 6SL7's, and I replied.
As for why Valve amplifiers sound more powerful, watt for watt, compared to Solid State designs, there are sevral theories, and ideas that have been put forward over the years, one is as Jez comented on, the softer clipping nature of valves compared to bipolar devices etc, however; IMHO there is more to it than that, one aspect to consider when comparing the two topologies, is to do with how the gain is controled and set around solid state devices compared to the open loop, linear nature of valves. And yes, again, IMHO, the fact that valves usualy run on much higher voltage rails than SS devices definately plays a part, of course, all of this is subjective, and I would welcome all other input and thoughts on this,I think it would make for a very interesting subject, but only if the OP doesent object. :)

I'm afraid our agreement parts company there Anthony:) I will say q=1/2cv^2 though ;) A big enough PSU on a SS amp nullifies it though...

[Marco]

however; IMHO there is more to it than that, one aspect to consider when comparing the two topologies, is to do with how the gain is controlled and set around solid state devices compared to the open loop, linear nature of valves. And yes, again, IMHO, the fact that valves usually run on much higher voltage rails than SS devices definitely plays a part, of course...

Higher voltage rails... Yes, that was the one! I can't comment on the technical points you've made, save to say that, like you, I'm convinced that there's more going on, in that respect, than soft clipping, which is confirmed by my extensive listening experiences, using a multitude of valve and SS amps over the years :)

It would be interesting to hear Paul, Nick, Alan and/or Andrew's opinions on this matter, or indeed any of the other registered 'techies' on the forum :cool:

Marco.

[anthonyTD]

And I respect that. :)

I'm afraid our agreement parts company there Anthony:) I will say q=1/2cv^2 though ;) A big enough PSU on a SS amp nullifies it though...

[Arkless Electronics]

Higher voltage rails... Yes, that was the one! I can't comment on the technical points you've made, save to say that, like you, I'm convinced that there's more going on, in that respect, than soft clipping, which is confirmed by my extensive listening experience in that area, and using a multitude of valve and SS amps over the years :)

It would be interesting to hear Paul, Nick, Alan and/or Andrew's opinions on this matter, or indeed any of the other registered 'techies' on the forum :cool:

Marco.

It would be great to have some more input yes. So long as we stay technical and away from subjectivism. Technical fact can be tested, measured and proven. As soon as it gets purely subjective all bets are off.... anyone can claim anything, no matter how ridiculous and without any basis in fact and "anything goes".

1A X 1000V = 1000W just as 1V x 1000A = 1000W so on the face of it high voltage cannot be it. However, the way in which valve amps use the voltage could have a link. High output impedance and poor damping etc means that valve amps are much less of a true Voltage source than SS amps. Hence they can't do the 50W into 8R, 100W into 4R, 200W into 2R that a really meaty SS amp can do. BUT, the SS amps output will not rise at all into a higher impedance neither. It can to some extent though with some valve amps and hence if a speaker is rated 8R but rises up to 20R at some frequencies (not unknown at all) and especially if this is in the mid range where our ears are most sensitive, the valve amp could produce over its rated power at some frequencies in a speaker dependent way. When operating under these conditions the distortion is likely to be really high as well, probably 10%+, and the distortion could help make it sound louder.

The waters are muddied on this by the fact that the valve amps most likely to soft clip in a big way, and sound subjectively louder due to this, are the same ones as are most likely to exhibit the effect I mentioned and the ones generally with the worst overall measured performance!

On the other hand a Radford with its high NFB and excellent measured performance can be expected to be most SS like in all this.

Another thing needs mentioning here. Most valve amps are class A and have huge power supplies relative to their output power. If we are comparing a 25W valve amp with a 25W SS one then the 25W SS amp needs to be something like a Mark Levinson 25WPC class A SS amp to give an even playing field.

Anthony, is the above where you're coming from on the high Voltage bit?

[montesquieu]

The Meishu is a lovely sounding beast. So you rate it as warmer sounding than the Oto SE?

s.

With the right speakers the Meishu can sound nice. With my Tannoy 15in Monitor Golds it sounded absolutely dreadful. (No damping factor worth speaking of, high output impedance - all that you don't want with a speaker that needs to be controlled like a big Tannoy).

[Marco]

It would be great to have some more input yes. So long as we stay technical and away from subjectivism. Technical fact can be tested, measured and proven. As soon as it gets purely subjective all bets are off.... anyone can claim anything, no matter how ridiculous and without any basis in fact and "anything goes".


So we've all just to shut up while you guys sit and talk in a 'foreign language'? ;)

It's ok, I know what you mean. It would definitely be interesting if we had more input from the 'techies' here, but if I read something that I can relate to through listening experience, and happen to agree or disagree with it, then I'll comment accordingly! :ner:

Marco.

[Marco]

With the right speakers the Meishu can sound nice.

Who the fuck wants "nice"? Get yer slippers on then and light your pipe. Certainly NOT me... I *demand* REAL!! ;)

Marco.

[anthonyTD]

Damping factor is another reason that is often put forward as the trump card, in favour of sold state amps over valves.
And yes, I agree, if we were feeding a perfect speaker load, the higher damping factor of SS amps would indeed be a major advantage, as far as bass and controling unwanted cone movement.
But think about this for a moment; most real world speakers have something in the way of the drivers that the amplifier will see first, in the case of the Woofer, or bass unit, you will have an inductor, and in the high frequency unit, or Tweeter, you will have at least a capacitor, and almost always a resistor.
Therefore; it can be seen that the huge diffrence in damping factor figures between valve amps and Solid state, becomes much less of a concern when considering the final load, ie; the Loud speaker!
As far as other reasons why valve amps tend to sound' watt for watt more powerful, and imediate than solid state amps of similar power output, consider this; A valve amp does not require negative feedback to enable it to function. The primary purpose of Negative feedback is to quieten the amp and provide some damping to the speaker. And infact' In comparison to SS amps, the amount of negative feedback that can be applied to a conventional valve amp circuit is quite small, any more than is necessary will push the circuit into oscillations and instability.

A pushpull Tetrode configured valve amp, [similar to Marco's amp] with no negative feedback, will attempt to provide a constant current at the secondary of the output transformer. As the Impedance of the speaker increases so does the Voltage from the output transformer. therefore; The output Voltage from the valve amp will rise in an attempt to maintain constant current to the speaker. If an imaginary speaker had no internal Reactance and behaved as a perfect 8ohm resistor, across a desired frequency spectrum, there would be IMHO little auditory difference between a valve and solid-state amp. All cone speakers are highly Reactive and their Impedance varies over the frequency spectrum, Therefore, because Valve and solid-state amps operate in opposite ways to how power is delivered into a changing Impedance, the resultant audible difference is very noticeable. Therefore With most cone speakers, many solid-state amps appear to sound flat and lifeless in comparison to a valve amp of similar power output etc.


Valve amp; power is directly proportional to speaker Impedance, therefore' power increases as the speaker Impedance rises.


Solid-state ; power is inversely proportional to speaker Impedance, therefore' power decreases as the speaker Impedance rises.

[montesquieu]

Who the fuck wants "nice"? Get yer slippers on then and light your pipe. Certainly NOT me... I *demand* REAL!! ;)

Marco.

The point I was making Marco is that the Meishu can sound 'nice' ie unobjectionable in an undemanding setting, but sounded absolutely shit with the Tannoys. A design like that is kneecapped by its limitations for the majority of real-world situations - something utterly predicted, as it happens by how it measures.

My experience has been that if something measures well, it generally sounds prety good at least within its design parameters. If something measures badly it will usually show up at the ears in short order.

Neither your Copper Amp nor my Radford was, as Jez put it, designed by 'ear' but instead are the product of solid design, measurement, and high quality bits where there are required.

Where I take issue is some of the kit around the place (especially the stuff coming out of China recycling proably ill-understood old circuits) that is designed on voodo principles rather than solid engineering. Got to be single-ended, got to have no NFB, got to be triode, and so on and so on. Yes, it's possible to make a good amp this way, with with expensive enough transformers and power supplies. But most of the amps following this fashion are, frankly, a bit shit and unless used with 100db horns or other kit of that ilk, this becomes apparent very quickly.

Valve vs SS, I've settled on valve but I'm open to SS as an approach, I'm particuarly interested in how Class D is evolving ... I started another thread asking 'is it there yet', I'm not sure it is but perhaps it's not that far away.

[Arkless Electronics]

So we've all just to shut up while you guys sit and talk in a 'foreign language'? ;)

It's ok, I know what you mean. It would definitely be interesting if we had more input from the 'techies' here, but if I read something that I can relate to through listening experience, and happen to agree or disagree with it, then I'll comment accordingly! :ner:

Marco.

Marco, My subjectivism, and as I keep on saying I am a subjectivist when it's justified, is in just this sort of thing. We KNOW something is going on we CAN measure it BUT we can't entirely equate what we measure with what we hear. This is what I would call "normal" subjectivism and it is essential if we are to correlate what we hear with measurements and thereby move the whole game forwards. It's the subjectivism of "voicing" an amp, the subjectivism of hearing a cart you know to be superb but after re-installation it's sounding off and you know the VTA, tracking force whatever is off.

Where we're from different planets is in things like fuses where we can easily scientifically prove that it does diddly squat, even if we measure to 6 decimal places of accuracy, and where all theory and common sense also says it could not possibly have any effect :)

[Arkless Electronics]

The point I was making Marco is that the Meishu can sound 'nice' ie unobjectionable in an undemanding setting, but sounded absolutely shit with the Tannoys. A design like that is kneecapped by its limitations for the majority of real-world situations - something utterly predicted, as it happens by how it measures.

My experience has been that if something measures well, it generally sounds prety good at least within its design parameters. If something measures badly it will usually show up at the ears in short order.

Neither your Copper Amp nor my Radford was, as Jez put it, designed by 'ear' but instead are the product of solid design, measurement, and high quality bits where there are required.

Where I take issue is some of the kit around the place (especially the stuff coming out of China recycling proably ill-understood old circuits) that is designed on voodo principles rather than solid engineering. Got to be single-ended, got to have no NFB, got to be triode, and so on and so on. Yes, it's possible to make a good amp this way, with with expensive enough transformers and power supplies. But most of the amps following this fashion are, frankly, a bit shit and unless used with 100db horns or other kit of that ilk, this becomes apparent very quickly.

Valve vs SS, I've settled on valve but I'm open to SS as an approach, I'm particuarly interested in how Class D is evolving ... I started another thread asking 'is it there yet', I'm not sure it is but perhaps it's not that far away.

Good post:) Completely agree with that.

[Marco]

Marco, My subjectivism, and as I keep on saying I am a subjectivist when it's justified, is in just this sort of thing. We KNOW something is going on we CAN measure it BUT we can't entirely equate what we measure with what we hear. This is what I would call "normal" subjectivism and it is essential if we are to correlate what we hear with measurements and thereby move the whole game forwards. It's the subjectivism of "voicing" an amp, the subjectivism of hearing a cart you know to be superb but after re-installation it's sounding off and you know the VTA, tracking force whatever is off.


Completely agree, and out with of designing equipment, I use precisely the same form of subjectivism, when assembling sonically (and musically) rewarding hi-fi systems. Virtually none of my current system has been evaluated or chosen on measurements. I simply used my experience, gut instincts and ears, and that approach has been successful and served me very well for the last 30-odd years :)


Where we're from different planets is in things like fuses where we can easily scientifically prove that it does diddly squat, even if we measure to 6 decimal places of accuracy, and where all theory and common sense also says it could not possibly have any effect...

Well... Only if it's 100% certain that you're measuring for the RIGHT thing, using the RIGHT apparatus, which is actually capable of providing the results needed! ;)

In my view, that's not always the case with what's often ignorantly dismissed as "foo"... We need to be cleverer, and look into things much deeper than only that which is immediately obvious [confirmed by currently accepted wisdom], or simply what appeases our 'belief system'/sensibilities (scientific or otherwise)!

Anyway, we're veering wildly off-topic, so let's leave that subject for another day :cool:

Marco.

[Arkless Electronics]

Damping factor is another reason that is often put forward as the trump card, in favour of sold state amps over valves.
And yes, I agree, if we were feeding a perfect speaker load, the higher damping factor of SS amps would indeed be a major advantage, as far as bass and controling unwanted cone movement.
But think about this for a moment; most real world speakers have something in the way of the drivers that the amplifier will see first, in the case of the Woofer, or bass unit, you will have an inductor, and in the high frequency unit, or Tweeter, you will have at least a capacitor, and almost always a resistor.
Therefore; it can be seen that the huge diffrence in damping factor figures between valve amps and Solid state, becomes much less of a concern when considering the final load, ie; the Loud speaker!
As far as other reasons why valve amps tend to sound' watt for watt more powerful, and imediate than solid state amps of similar power output, consider this; A valve amp does not require negative feedback to enable it to function. The primary purpose of Negative feedback is to quieten the amp and provide some damping to the speaker. And infact' In comparison to SS amps, the amount of negative feedback that can be applied to a conventional valve amp circuit is quite small, any more than is necessary will push the circuit into oscillations and instability.

A pushpull Tetrode configured valve amp, [similar to Marco's amp] with no negative feedback, will attempt to provide a constant current at the secondary of the output transformer. As the Impedance of the speaker increases so does the Voltage from the output transformer. therefore; The output Voltage from the valve amp will rise in an attempt to maintain constant current to the speaker. If an imaginary speaker had no internal Reactance and behaved as a perfect 8ohm resistor, across a desired frequency spectrum, there would be IMHO little auditory difference between a valve and solid-state amp. All cone speakers are highly Reactive and their Impedance varies over the frequency spectrum, Therefore, because Valve and solid-state amps operate in opposite ways to how power is delivered into a changing Impedance, the resultant audible difference is very noticeable. Therefore With most cone speakers, many solid-state amps appear to sound flat and lifeless in comparison to a valve amp of similar power output etc.


Valve amp; power is directly proportional to speaker Impedance, therefore' power increases as the speaker Impedance rises.


Solid-state ; power is inversely proportional to speaker Impedance, therefore' power decreases as the speaker Impedance rises.

On the damping factor bit, this is why I said in an earlier post that it is debatable whether output impedances below about 0.3R are necessary. Much depends on the speaker load though. If a speaker dips to 2R then lower still would definitely be desirable.

On your next point. SS amps can also be made to work fine with no feedback at all...

Your last paragraph is precisely what I said earlier in #102 but rephrased. Where I would disagree is in the "Valve amp; power is directly proportional to speaker Impedance, therefore' power increases as the speaker Impedance rises". One would never use a tetrode or pentode amp without negative feedback as it would then be a current source and have no damping factor at all. With low-ish feedback this effect will come into play to an extent of course, which is what I was getting at. Even with triodes and zero feedback it will happen to an extent. The degree to which power rises with increased load impedance is far less though than the amount it will increase with falling load impedance with a SS amp. Unless you deliberately make the valve amp a current source as in your example but this is completely undesirable in any amplifier and would never be done in practice.

[Arkless Electronics]

Completely agree, and out with of designing equipment, I use precisely the same form of subjectivism, when building sonically (and musically) rewarding hi-fi systems. Virtually none of my current system has been evaluated or chosen on measurements. I simply used my experience, gut instincts and ears, and that approach has been successful and served me very well for the last 30-odd years :)



Well... Only if it's 100% certain that you're measuring for the RIGHT thing, using the RIGHT apparatus, which is actually capable of providing the results needed! In my view, that's not always the case with what's often ignorantly dismissed as "foo"...

Anyway, we're veering wildly off-topic, so let's leave that subject for another day :cool:

Marco.

Amen to that:)

[pgarrish]

I must either be extremely lucky with my amps, have a crap system, or crap ears cos I can hear virtually no difference between my 180wpc PA style SS amp and a pair of very old, hand built 18wpc Mullard 5-20 monoblocks. My Tannoys are a fairly benign load which probably helps. My main problem is the valves don't go loud enough from my TT - 180wpc definitely beats 18 in that situation :)

[montesquieu]

I must either be extremely lucky with my amps, have a crap system, or crap ears cos I can hear virtually no difference between my 180wpc PA style SS amp and a pair of very old, hand built 18wpc Mullard 5-20 monoblocks. My Tannoys are a fairly benign load which probably helps. My main problem is the valves don't go loud enough from my TT - 180wpc definitely beats 18 in that situation :)

Very likely an input sensitivity question rather than anything to do with power rating.

[pgarrish]

Very likely an input sensitivity question rather than anything to do with power rating.

My tt seems to have a very low output. And I use a passive pre with the valves which doesn't help much. The valves are very sensitive compared to the big amp, the tt is just very quiet...

[struth]

I must either be extremely lucky with my amps, have a crap system, or crap ears cos I can hear virtually no difference between my 180wpc PA style SS amp and a pair of very old, hand built 18wpc Mullard 5-20 monoblocks. My Tannoys are a fairly benign load which probably helps. My main problem is the valves don't go loud enough from my TT - 180wpc definitely beats 18 in that situation :)

a little more gain on phono stage would cure that :). I must be similarly lucky as I seem to get decent systems most times, that just require a bit of fettling. Ive a rule nowadays.. get speakers you like and then get an amp to suit. Try to spend as little as possible yet get decent stuff... spend the rest of fine whisky and records...now just records

[montesquieu]

My tt seems to have a very low output. And I use a passive pre with the valves which doesn't help much. The valves are very sensitive compared to the big amp, the tt is just very quiet...

May not be the best place for a passive in that case ...

[Arkless Electronics]

The Mullard 5-20 was (like the Radford STA25) very conservatively rated on power output and should in practice manage about 30WPC. Into big Tannoys this should give all the loud any sane person can handle!!

[anthonyTD]

Sorry, I didnt get chance to read your earlier post Jez,:)
The point I was trying to make with the Tetrode ouput stage was; even with the permisable amount of feedback aplied, [which as we know would be small] the amp would still try and maintain a relatively constant power output into the varying speaker load!
The copper amps also have ultra-linear output configuration [43%] I will try and explain in as simple a way as posible, for those here who are interested, but not necesarily technicaly minded, Ultra-linear is where The Screen grid, of a tetrode, or pentode valve [instead of being connected to a fixed positive supply] is connected to an Aditional tapping on the output transformer, which inturn acts as a second Grid modulating the gain of the valve in opposite phase to the Anode. This return path acts as an automatic Negative feedback, that removes most' if not all residual distortion created by the output valves and output transformer, Also' this local feedback from the 43% primary taps to the Screen, results in the speaker connected to the secondary being included in the UL feedback structure. The output Impedance from the secondary winding tends to reflect the speaker Impedance. The result being; the reflected Impedance tends to naturally maintain constant power to the speaker, over the frequency spectrum, and providing aditional damping, which is obviously another positive for the valve amp.

On the damping factor bit, this is why I said in an earlier post that it is debatable whether output impedances below about 0.3R are necessary. Much depends on the speaker load though. If a speaker dips to 2R then lower still would definitely be desirable.

On your next point. SS amps can also be made to work fine with no feedback at all...

Your last paragraph is precisely what I said earlier in #102 but rephrased. Where I would disagree is in the "Valve amp; power is directly proportional to speaker Impedance, therefore' power increases as the speaker Impedance rises". One would never use a tetrode or pentode amp without negative feedback as it would then be a current source and have no damping factor at all. With low-ish feedback this effect will come into play to an extent of course, which is what I was getting at. Even with triodes and zero feedback it will happen to an extent. The degree to which power rises with increased load impedance is far less though than the amount it will increase with falling load impedance with a SS amp. Unless you deliberately make the valve amp a current source as in your example but this is completely undesirable in any amplifier and would never be done in practice.

[Marco]

The point I was making Marco is that the Meishu can sound 'nice' ie unobjectionable in an undemanding setting, but sounded absolutely shit with the Tannoys. A design like that is kneecapped by its limitations for the majority of real-world situations - something utterly predicted, as it happens by how it measures.


Oh I know, mate. My reply was a little tongue-in-cheek, but at the same time outlining that I'd never want any amp (valve or SS) that simply sounded "nice"...

"Nice", to me, means pleasant or inoffensive, and ultimately coloured and boring sounding - and nothing like real music. I don't 'do' sound-effects devices, posing as audio amplifiers! :nono:

That said, we're in entire agreement with the rest of what you wrote :)

Marco.

[Arkless Electronics]

Sorry, I didnt get chance to read your earlier post Jez,:)
The point I was trying to make with the Tetrode ouput stage was; even with the permisable amount of feedback aplied, [which as we know would be small] the amp would still try and maintain a relatively constant power output into the varying speaker load!
The copper amps also have ultra-linear output configuration [43%] I will try and explain in as simple a way as posible, for those here who are interested, but not necesarily technicaly minded, Ultra-linear is where The Screen grid, of a tetrode, or pentode valve [instead of being connected to a fixed positive supply] is connected to an Aditional tapping on the output transformer, which inturn acts as a second Grid modulating the gain of the valve in opposite phase to the Anode. This return path acts as an automatic Negative feedback, that removes most' if not all residual distortion created by the output valves and output transformer, which is obviously another positive for the valve amp.

:) I nearly edited my post to add "provided the tetrode/pentode amp is not ultralinear and doesn't use partial cathode coupling the no feedback = unusabley high output impedance applies"! Ultralinear gives most of the low distortion of triodes with most of the power of tetrodes/pentodes.

[Arkless Electronics]

Just had a look at my original copy of "Circuits for audio amplifiers" by Mullard and yes the 5-20 should give 30-32W in practice. It also claims 0.05% THD @ 20W and the output impedance as 0.3R. A fairly high 30dB of NFB is used.

[anthonyTD]

:)
:) I nearly edited my post to add "provided the tetrode/pentode amp is not ultralinear and doesn't use partial cathode coupling the no feedback = unusabley high output impedance applies"! Ultralinear gives most of the low distortion of triodes with most of the power of tetrodes/pentodes.

[anthonyTD]

A good discusion so far, and one that I have enjoyed reading, and contributing to :)
Now its past my bedtime folks, so I will bid you goodnight, and hopefuly' catch up with things tomorow.
A...

[pgarrish]

Just had a look at my original copy of "Circuits for audio amplifiers" by Mullard and yes the 5-20 should give 30-32W in practice. It also claims 0.05% THD @ 20W and the output impedance as 0.3R. A fairly high 30dB of NFB is used.

Apparently mine run at low voltage so they are down on power but should last longer.. (so said Haden Boardman when he restored them). The valves are all original for 58/60 when built including a rather swish mil-spec gz34(?) rectifier :)

They are loud enough 'most' of the time.... but sometimes you want a little extra oomph!

[spendorman]

The Mullard 5-20 was (like the Radford STA25) very conservatively rated on power output and should in practice manage about 30WPC. Into big Tannoys this should give all the loud any sane person can handle!!

Absolutely, about 1970 my uncle had an amplifier of similar power, Rogers Master with EL34's into Tannoy 12" Silver Dual Concentrics, in quite a large room. I remember turning the volume up on that, thought "this sounds good, more than sufficient power".

[Reffc]

The Mullard 5-20 circuit is still doing the rounds on a lot of amplifiers today in various guises, and for good reason. I've been following with interest, and some points made RE damping factor, I did in fact made some posts back (lost in the debate). I'm following the feedback V's no feedback arguments for design, and am of the opinion that both can work equally well, but one of the primary reasons to use it for valve amplifiers is to get the output impedance low. Again, I made the point that few use it because some can't be had with the design needed to handle the instability if time compensation isn't properly applied. Designs such as Toms and my own STA25 do use a lot of it, 26dB compared with the 5-20's 30dB, and remain perfectly stable due to a well designed compensation circuit and indeed the STA design shares some similarity with the 5-20. I remember Will providing the specifications and far from dropping as low as Jez suggests, the design has plenty power reserve at 20Hz because it has been thought about and is designed well, and has low THD throughout the operating bandwidth. The specs are (-1dB)25 Watts from 20Hz to 40KHz; 36watts from 25Hz - 25KHz with just 0.1% THD at 25W output. That's nothing like as low powered into 20W as was suggested earlier, so with a decent damping factor, will compare very favourably to any equivalent SS amp into something as sensitive as the Tannoys, which have a minimum impedance of just 7.2 Ohms. (average of measurements taken from MGs and HPDs)

It is also worth remembering that some passive 'speaker designs don't have the losses quoted earlier of a typical 0.6R. For a typical 3 to 4m speaker cable run using a 16AWG cable has a cable loop resistance of about 0.11 Ohms. My own RFC Reference crossovers have losses in the bass circuit of just 0.13 Ohms at DC (compared with the 0.6 quoted earlier) giving a total load of 0.24. Ohms. If we round that up to 0.25 and add to say a Radford output impedance of 0.18 ohms, we have a total of .43 Ohms. Minimum speaker load is 7.2 ohms which gives a damping factor of 16.7 which is more than enough for vice like bass grip. Compare with a SS device of say 0.05 ohms output impedance. Total impedance will be .3 ohms and damping factor 24. The reality is that once past a DF of 12 to 15 or so, any more is not adding a great deal to the grip. Even of an amp had zero output impedance (the ideal), maximum DF would still only be 29 or so, not the 200 or 300 that some manufacturers claim because they neglect to include cable and crossover losses. So the summary is a healthy DF and plenty of power into 25Hz with speakers having around a 92dB/1w sensitivity. In such cases, it is not game, set or match, but more what you prefer to listen with.

Like Tom, I'm open to any design, be it SS or valve, and have heard a lot of really quite decent SS amps with the Tannoys. Most though have been in the same price ball-park as the valve amps, save one or two, and there's something which just seems to give more life to the music with a really good valve amp, so for the time being, that's where my preference lays. As with Tom, I'm watching with interest where Class D is going, but consider it still somewhat in it's infancy with regard to availability of some really worthy designs for now.

[anthonyTD]

Its all gone a bit quiet here now :D
Ohh well, I hope that what has been discussed here so far' has given the original poster of the thread some food for thought, on the posible merits, and pitfalls of both technologies. :)
A...

[JohnJo]

Its all gone a bit quiet here now :D
Ohh well, I hope that what has been discussed here so far' has given the original poster of the thread some food for thought, on the posible merits, and pitfalls of both technologies. :)
A...

Any chance of a photo or two of *your* copper amp Anthony?

Seen Marco's and Joe's :)

Edit: Is that it in your avatar? 8 x KT88?

[Gazjam]

Any chance of a photo or two of *your* copper amp Anthony?

Seen Marco's and Joe's :)

Edit: Is that it in your avatar? 8 x KT88?

Another Copper valve amp John?...top plate's copper?

http://i434.photobucket.com/albums/qq61/gazjamster/Kit%20pics/Nick%20Amp/20160930_184822_zpsv82ulzpl.jpg

[anthonyTD]

Hi John,
Yes, its the one in the avatar, Its not a very good pick, I will try and put up a better one.:)
A...
Any chance of a photo or two of *your* copper amp Anthony?

Seen Marco's and Joe's :)

Edit: Is that it in your avatar? 8 x KT88?

[Arkless Electronics]

The Mullard 5-20 circuit is still doing the rounds on a lot of amplifiers today in various guises, and for good reason. I've been following with interest, and some points made RE damping factor, I did in fact made some posts back (lost in the debate). I'm following the feedback V's no feedback arguments for design, and am of the opinion that both can work equally well, but one of the primary reasons to use it for valve amplifiers is to get the output impedance low. Again, I made the point that few use it because some can't be had with the design needed to handle the instability if time compensation isn't properly applied. Designs such as Toms and my own STA25 do use a lot of it, 26dB compared with the 5-20's 30dB, and remain perfectly stable due to a well designed compensation circuit and indeed the STA design shares some similarity with the 5-20. I remember Will providing the specifications and far from dropping as low as Jez suggests, the design has plenty power reserve at 20Hz because it has been thought about and is designed well, and has low THD throughout the operating bandwidth. The specs are (-1dB)25 Watts from 20Hz to 40KHz; 36watts from 25Hz - 25KHz with just 0.1% THD at 25W output. That's nothing like as low powered into 20W as was suggested earlier, so with a decent damping factor, will compare very favourably to any equivalent SS amp into something as sensitive as the Tannoys, which have a minimum impedance of just 7.2 Ohms. (average of measurements taken from MGs and HPDs)

It is also worth remembering that some passive 'speaker designs don't have the losses quoted earlier of a typical 0.6R. For a typical 3 to 4m speaker cable run using a 16AWG cable has a cable loop resistance of about 0.11 Ohms. My own RFC Reference crossovers have losses in the bass circuit of just 0.13 Ohms at DC (compared with the 0.6 quoted earlier) giving a total load of 0.24. Ohms. If we round that up to 0.25 and add to say a Radford output impedance of 0.18 ohms, we have a total of .43 Ohms. Minimum speaker load is 7.2 ohms which gives a damping factor of 16.7 which is more than enough for vice like bass grip. Compare with a SS device of say 0.05 ohms output impedance. Total impedance will be .3 ohms and damping factor 24. The reality is that once past a DF of 12 to 15 or so, any more is not adding a great deal to the grip. Even of an amp had zero output impedance (the ideal), maximum DF would still only be 29 or so, not the 200 or 300 that some manufacturers claim because they neglect to include cable and crossover losses. So the summary is a healthy DF and plenty of power into 25Hz with speakers having around a 92dB/1w sensitivity. In such cases, it is not game, set or match, but more what you prefer to listen with.

Like Tom, I'm open to any design, be it SS or valve, and have heard a lot of really quite decent SS amps with the Tannoys. Most though have been in the same price ball-park as the valve amps, save one or two, and there's something which just seems to give more life to the music with a really good valve amp, so for the time being, that's where my preference lays. As with Tom, I'm watching with interest where Class D is going, but consider it still somewhat in it's infancy with regard to availability of some really worthy designs for now.

I repeat for the third time that Radfords are not normal valve amplifiers and so picking probably the best valve amp ever made and using it as representative of valve amplifiers is hardly erm... representative! Also IIRC it has 36dB of NFB. Also I repeat that there is no such thing as time compensation.
Oh and most valve amps do use feedback!
The only factor that matters in maintaining the output power down to 20Hz is the physical size of the output transformer...
I stick by what I said on game set and match to SS on bass performance 100%. and stress again that although, on average, SS amps will be 10 X or more better than valve ones at the bottom end, valve amps can easily be good enough for it to not be particularly noticeable subjectively. Whilst it can be amazing what the human ear is capable of in some areas it is also surprising how tolerant of gross errors it is in others!

[RothwellAudio]

I'll just chip in here with some general comments which (I think) address the OP's question.
Firstly, I think it's a mistake to assume that there's a "valve sound" and all valve amps have it, or that there's a "transistor sound" and all transistor amps have it. The cliches about "warm and lush" for valves and "hard and aggressive" for transistors are just gross generalisations.

The benefits of valves are that you can have something which looks cool (ironically, since it's actually hot) and sets you apart from your non-audiophile mates, keeps your house warm in winter and can sound extremely good - if it's a good amp.
The cons are that some maintenance will be required, the amp will cost a lot more than an SS amp of similar power (probably) and your electricity bills will go up.
I wouldn't want to generalise beyond that.

[anthonyTD]

:)
I'll just chip in here with some general comments which (I think) address the OP's question.
Firstly, I think it's a mistake to assume that there's a "valve sound" and all valve amps have it, or that there's a "transistor sound" and all transistor amps have it. The cliches about "warm and lush" for valves and "hard and aggressive" for transistors are just gross generalisations.

The benefits of valves are that you can have something which looks cool (ironically, since it's actually hot) and sets you apart from your non-audiophile mates, keeps your house warm in winter and can sound extremely good - if it's a good amp.
The cons are that some maintenance will be required, the amp will cost a lot more than an SS amp of similar power (probably) and your electricity bills will go up.
I wouldn't want to generalise beyond that.

[JohnJo]

Another Copper valve amp John?...top plate's copper?

http://i434.photobucket.com/albums/qq61/gazjamster/Kit%20pics/Nick%20Amp/20160930_184822_zpsv82ulzpl.jpg

Very nice, that looks proper!

[Marco]

I repeat for the third time that Radfords are not normal valve amplifiers and so picking probably the best valve amp ever made and using it as representative of valve amplifiers is hardly erm... representative!

Yes, but surely all that matters is that the *actual topology* in question (i.e. valve-based electronics) is capable of said performance, regardless of whether Radfords are representative of your average valve amp?

If the topology itself wasn't capable of producing the measured performance in the first place, as cited by Paul, then he wouldn't have used it as an example to back up his argument. Furthermore, if the majority of other valve amps fail to measure up to the Radford, then that's not its fault (or the designer's) - it's up to other manufacturers to up their game accordingly!

It's a bit like quoting and marvelling over the technical specs of a Bugatti Veyron, and citing how it's a shining example of automotive technology, and then a dissenter saying: 'Ah yes, but it's hardly representative of your average car...!' ;)

Marco.

[Macca]

Can't add to the technical stuff but will say

1) worst expensive systems I have ever heard all used valve amps. May not have always been the amps fault but there is deffo some really expensive rubbish in the valve world. Not so much with SS, you seem to get what you pay for there.

2) Did not know about the technical superiority of Radfords until recently, but I had already concluded several years ago that it is one of the best amps of any topology I have ever heard. An STA 25 sold here not long ago for £1200 so not much money for something so good, if you can get away with 25 watts of course.

3) At the top levels there is little to choose between them. Although single ended valve amps have their own flavour that no other topology seems to be able to mimic. Seriously low power is the drawback.

4) For me personally valves are too much faff. But I am pretty lazy. I also don't like that they slowly degrade, so slowly you can't hear it. That would get my audiophilia nervosa going a treat.

[Reffc]

I repeat for the third time that Radfords are not normal valve amplifiers and so picking probably the best valve amp ever made and using it as representative of valve amplifiers is hardly erm... representative! Also IIRC it has 36dB of NFB. Also I repeat that there is no such thing as time compensation.
Oh and most valve amps do use feedback!
The only factor that matters in maintaining the output power down to 20Hz is the physical size of the output transformer...
I stick by what I said on game set and match to SS on bass performance 100%. and stress again that although, on average, SS amps will be 10 X or more better than valve ones at the bottom end, valve amps can easily be good enough for it to not be particularly noticeable subjectively. Whilst it can be amazing what the human ear is capable of in some areas it is also surprising how tolerant of gross errors it is in others!

Radfords are an example of a competently designed valve amplifier Jez, and they are not alone in that, though I agree, there is a plethora of poorly designed ones doing the rounds (and not all at bargain basement prices!).

The feedback figure is correct and is taken from Radford's own literature which states in section 2.5 (below) that "...A low inherent output stage resistance is achieved by using anode/screen feedback.....and then applying 26dB overall amplifier feedback..."

http://www.radfordrevival.co.uk/wordpress/wp-content/uploads/2011/11/Series-3-Leaflet-P3.jpg

As for most valve amps using feedback, many do, but many do not. I have owned a few myself which used zero negative feedback (driving very efficient loudspeakers). OK, lets re-phrase the time compensation. As distortion reduction can be proportional to amount of feedback used, then in theory, the more that is used the better. However, as stated within the Radford design literature, the amount used is a function of the phase shift at low and high frequencies. As oscillation can occur at the frequency extremes, then it becomes necessary to reduce gain at these extremes to zero, where the phase shift becomes 180 degrees. That is all that I meant by "time" compensation, ie, that it is derived because at specific frequencies where phase shift becomes 180 degrees, oscillation and instability would occur otherwise.

I have seen examples of valve amps using negative feedback without any compensation, and they are probably not very stable as a result.

As for the ONLY aspect of power output being the size of the transformer, that's not entirely correct either! That may have been the case 40 years ago, but don't forget that, for example, the advent of modern grain oriented Silicon steel cores has allowed more compact output transformers to be used so they don't have to be the size of a small bus to get the power gains at modest sizes....mind you, the Emille I had did use output transformers that probably were the size of a small bus!

[Arkless Electronics]

Radfords are an example of a competently designed valve amplifier Jez, and they are not alone in that, though I agree, there is a plethora of poorly designed ones doing the rounds (and not all at bargain basement prices!).

The feedback figure is correct and is taken from Radford's own literature which states in section 2.5 (below) that "...A low inherent output stage resistance is achieved by using anode/screen feedback.....and then applying 26dB overall amplifier feedback..."

http://www.radfordrevival.co.uk/wordpress/wp-content/uploads/2011/11/Series-3-Leaflet-P3.jpg

As for most valve amps using feedback, many do, but many do not. I have owned a few myself which used zero negative feedback (driving very efficient loudspeakers). OK, lets re-phrase the time compensation. As distortion reduction can be proportional to amount of feedback used, then in theory, the more that is used the better. However, as stated within the Radford design literature, the amount used is a function of the phase shift at low and high frequencies. As oscillation can occur at the frequency extremes, then it becomes necessary to reduce gain at these extremes to zero, where the phase shift becomes 180 degrees. That is all that I meant by "time" compensation, ie, that it is derived because at specific frequencies where phase shift becomes 180 degrees, oscillation and instability would occur otherwise.

I have seen examples of valve amps using negative feedback without any compensation, and they are probably not very stable as a result.

As for the ONLY aspect of power output being the size of the transformer, that's not entirely correct either! That may have been the case 40 years ago, but don't forget that, for example, the advent of modern grain oriented Silicon steel cores has allowed more compact output transformers to be used so they don't have to be the size of a small bus to get the power gains at modest sizes....mind you, the Emille I had did use output transformers that probably were the size of a small bus!

Other than my falsely remembering the NFB as 36dB when it is in fact 26dB I stand by every word I said. Oh and having this time read up the specs it seems the output impedance is actually 0.45R and so right in the middle of the range I gave as typical.... I've still got something in the old grey cells saying 36dB so maybe that is for the STA100.. I can't find a figure for this after a quick search though. Certainly 36dB is very high for a valve amp if so....

The vast majority of valve amps for hi fi use have NFB. It would also be very unusual to find one without NFB that doesn't feature big triodes, usually directly heated, as output valves as triodes have inherently low output impedance for a valve and so if you don't mind an output impedance from the amp as a whole of as high as 3R or more (I do!) they can be used without feedback. I'll say as a guesstimate that of all hi fi valve amps ever built at least 90% use feedback.

Grain orientated silicon steel laminations have been around for donkeys years! Also size is indeed everything here so yep, I am entirely correct.

No point in re-phrasing time compensation as there is no such thing. I gathered you meant phase compensation but for the sake of accuracy....

I also disagree with both you and Marco over the choice of the Radford as an example. Bizarrely Marco gives the same ish example I was going to myself so yes lets stick to the automotive analogy. To me it would seem very silly to name a Bugatti Veyron as a typical example of a motor car and to then say that Mondeo's, Uno's, Xantia's, BMW 3 series etc were all absolutely shite cars cos they fall so far short of the performance of the Veyron!! :mental:

[Radford Revival]

(Posting just to take my mind off unfortunate events in our personal lives right now)


Other than my falsely remembering the NFB as 36dB when it is in fact 26dB I stand by every word I said. Oh and having this time read up the specs it seems the output impedance is actually 0.45R and so right in the middle of the range I gave as typical....


Hi Jez

For once for a specsheet, the Radfords actually better what is quoted. On the 8 ohm tap with good valves it is as low as 0.18 ohm in the midband (measured), on the 16 ohm tap it's around about 0.3ish from memory, and around 0.10 on the 4ohm setting. It does rise slightly at either frequency extreme as per circuitry limitations. Pretty good though!

[montesquieu]

Hi John,
Yes, its the one in the avatar, Its not a very good pick, I will try and put up a better one.:)
A...

8 x KT88?

Don't forget a pic of the crane required to lift it ...

[Marco]

I also disagree with both you and Marco over the choice of the Radford as an example. Bizarrely Marco gives the same ish example I was going to myself so yes lets stick to the automotive analogy. To me it would seem very silly to name a Bugatti Veyron as a typical example of a motor car and to then say that Mondeo's, Uno's, Xantia's, BMW 3 series etc were all absolutely shite cars cos they fall so far short of the performance of the Veyron!! :mental:

Yes, Jez, but that's not what I'm saying.

The point is, in order to showcase the *pinnacle* of what something (anything) is capable of, you cite the best possible example of such you can think of, which is why I believe Paul opted for the Radford, in order to convey his point about what valve amps are capable of at their best, which for some reason in your last post you thought was daft (at least that's how it came across to me).

Personally, although I love the Radford and acknowledge its technical excellence, the best P/P valve amp I've heard so far is Anthony's Copper amp design, further modified with some of the best components currently available, and so I'd nominate that, ahead of the Radford, as a shining example of what valve technology is capable of at its best. Just my own personal opinion. And I'd also put Nick Gorham's designs into the same category.

Incidentally, as an aside, in reference to my own Copper amp and its claimed power output... About 4 years ago, at the same time as some 'boutique components' were installed, as mentioned above, the original mains transformer was also upgraded with a much bigger (higher specified and taller-stacked) one from Sowter. Anthony can correct me here if necessary, but I think that and how the (then KT120s) were subsequently biased, increased the amp's output from 30W Class A, to 50W.

Also, the output transformers on the Copper amp are very large, hand-wound affairs, built by a guy (I believe) called Peter Chappell, who used to work for GEC. This guy is top-notch and really knows his stuff, which may help explain the excellent wide-bandwidth and flat frequency response that the amp is capable of delivering.

Again, Anthony can (and I'm sure will) correct me on any of the above if necessary :cool:

Marco.

[JohnJo]

(Posting just to take my mind off unfortunate events in our personal lives right now)

:thumbsup:

[TheMooN]

Radfords are an example of a competently designed valve amplifier Jez,!

Having owned close to every amplifier manufactured during this period IMHO I prefered the additional organic texture of the Pye HF25 over the Radford http://www.audiomods.co.uk/pye1.html

[Arkless Electronics]

(Posting just to take my mind off unfortunate events in our personal lives right now)




Hi Jez

For once for a specsheet, the Radfords actually better what is quoted. On the 8 ohm tap with good valves it is as low as 0.18 ohm in the midband (measured), on the 16 ohm tap it's around about 0.3ish from memory, and around 0.10 on the 4ohm setting. It does rise slightly at either frequency extreme as per circuitry limitations. Pretty good though!

That is excellent for a valve amp yes! I was actually rather surprised to see 0.45R on the spec as I thought Paul's figure was about right on this and recalled seeing a similar figure quoted elsewhere myself. Also although the Mullard 5-20 is very good at 0.3R I was surprised that according to the spec it beat the Radford...

The distortion seemed too low for the amount of feedback needed to give that distortion figure to not also result in less than 0.45R also...

[montesquieu]

Radfords eh? Not wanting to do any willy-waving, but ...

http://www.radfordrevival.co.uk/wordpress/wp-content/uploads/2011/11/STA100-Leaflet-P2.jpg

Mine is slightly different, Will having wound me dedicated 8 ohm transformers (6 ohm actually I think) specially for the Tannoys, so it no longer has the 100v line or 16 ohm options.

IRC after Valvebloke did his magic on it, bringing it back from the dead, it measured even better than this ...

[Gazjam]

Having owned close to every amplifier manufactured during this period IMHO I prefered the additional organic texture of the Pye HF25 over the Radford http://www.audiomods.co.uk/pye1.html

Heard em both.
This is the Truth...

[Gazjam]

That is excellent for a valve amp yes! I was actually rather surprised to see 0.45R on the spec as I thought Paul's figure was about right on this and recalled seeing a similar figure quoted elsewhere myself. Also although the Mullard 5-20 is very good at 0.3R I was surprised that according to the spec it beat the Radford...

The distortion seemed too low for the amount of feedback needed to give that distortion figure to not also result in less than 0.45R also...

Jez,
bit of an aside (I guess?) but lovin the new mellow flava :)

[Gazjam]

[QUOTE=Radford Revival;827586](Posting just to take my mind off unfortunate events in our personal lives right now)

This. :thumbsup:
Hope all ok.

[spendorman]

(Posting just to take my mind off unfortunate events in our personal lives right now)

Sorry to hear this, I wish you more fortunate times.

I have sometimes posted to take my mind off unfortunate happenings in the last few years, and there have been several.

[anthonyTD]

Something I meant to comment on at the time but forgot.
If you check out the original GEC 100 Watt Circuit,http://www.oestex.com/tubes/Circuits/GEC100w.gif using a pair of KT88's you will notice that it uses no over-all feedback at all, however; its ouput stage is ultra-linear configured.:)
I have actualy heard a completed stereo version of this amp [I supplied the chassis]and it works very well considering.

One would never use a tetrode or pentode amp without negative feedback as it would then be a current source and have no damping factor at all. With low-ish feedback this effect will come into play to an extent of course, which is what I was getting at. Even with triodes and zero feedback it will happen to an extent. The degree to which power rises with increased load impedance is far less though than the amount it will increase with falling load impedance with a SS amp. Unless you deliberately make the valve amp a current source as in your example but this is completely undesirable in any amplifier and would never be done in practice.

[Arkless Electronics]

Something I meant to comment on at the time but forgot.
If you check out the original GEC 100 Watt Circuit,http://www.oestex.com/tubes/Circuits/GEC100w.gif using a pair of KT88's you will notice that it uses no over-all feedback at all, however; its ouput stage is ultra-linear configured.:)
I have actualy heard a completed stereo version of this amp [I supplied the chassis]and it works very well considering.

We were already in agreement over UL of course.... :)
I have an original copy of the GEC amplifiers pamphlet that I ordered from the factory when I was about 13!

[spendorman]

This looks interesting:

https://youtu.be/BnR_DLd1PDI

[montesquieu]

Some oddball designs by Time de Paravicini fall in this category as well .. EAR 861, push pull EL519s, no global negative feedback, supposedly pure Class A (presumably up to the distortion specs at least), uses 'Enhanced Triode Mode' (whatever that is - maybe some variant of ultralinear?) and a custom 'quadrafillar' output transformer. I have to say its performance with my current-hungry Tannoys was pretty outstanding even with a meagre 32 watts, pretty close to what my PP KT88-specced (KT90-equipped) Radford STA100 manages.

[walpurgis]

I have a friend who uses an EAR 861 to drive Tannoys. It's a very nice sounding amp.

Although he does like his Monarchy Audio SM-70 Pro just as much.

[Arkless Electronics]

Some oddball designs by Time de Paravicini fall in this category as well .. EAR 861, push pull EL519s, no global negative feedback, supposedly pure Class A (presumably up to the distortion specs at least), uses 'Enhanced Triode Mode' (whatever that is - maybe some variant of ultralinear?) and a custom 'quadrafillar' output transformer. I have to say its performance with my current-hungry Tannoys was pretty outstanding even with a meagre 32 watts, pretty close to what my PP KT88-specced (KT90-equipped) Radford STA100 manages.

If it's anything like the EAR 509, 519 and lots of other TdP designs then it's pretty much the opposite of your description! They are certainly unusual though yes. There are several feedback loops but non from the secondary of the OPT. It has UL taps from OPT to screen grids, cathode windings a la Quad II and Mcintosh and then the anodes of one phase are cross-coupled to the cathodes of the other by electrolytic caps.. other taps bootstrap the driver stage and another winding is used just to provide balanced feedback to the cathodes of the driver stage and globally(ish) to the input stage.

It's pretty clever stuff and they usually both sound and measure very good. I got to know Tim a bit when working for MF and then Alchemist.. an interesting bloke.

I'll bet not many remember the Michaelson Audio Chronos pre and power? A few may with the incredibly unreliable Odysseus:eek:

[montesquieu]

If it's anything like the EAR 509, 519 and lots of other TdP designs then it's pretty much the opposite of your description! They are certainly unusual though yes. There are several feedback loops but non from the secondary of the OPT. It has UL taps from OPT to screen grids, cathode windings a la Quad II and Mcintosh and then the anodes of one phase are cross-coupled to the cathodes of the other by electrolytic caps.. other taps bootstrap the driver stage and another winding is used just to provide balanced feedback to the cathodes of the driver stage and globally(ish) to the input stage.

It's pretty clever stuff and they usually both sound and measure very good. I got to know Tim a bit when working for MF and then Alchemist.. an interesting bloke.

I'll bet not many remember the Michaelson Audio Chronos pre and power? A few may with the incredibly unreliable Odysseus:eek:

Interesting to hear a professional's opinion ... I've generally liked his stuff a lot and have I've owned a bit of his gear - 509 monoblocks (the only one of his I found a bit 'meh' TBH), V20 (loved that especially after having some decent componets swapped out for the basic stuff it had in), 899 (also the Actue CD and MC3 SUT), also heard a fair few as well, the best of which was the 534 ... to my ears the 861 was the best of the lot. Also had an Odysseus yonks ago ... mechanical hum drove me potty but it was actually a nice performer. Didn't have it long enough for it to break down though ...

[Arkless Electronics]

Interesting to hear a professional's opinion ... I've generally liked his stuff a lot and have I've owned a bit of his gear - 509 monoblocks (the only one of his I found a bit 'meh' TBH), V20 (loved that especially after having some decent componets swapped out for the basic stuff it had in), 899 (also the Actue CD and MC3 SUT), also heard a fair few as well, the best of which was the 534 ... to my ears the 861 was the best of the lot. Also had an Odysseus yonks ago ... mechanical hum drove me potty but it was actually a nice performer. Didn't have it long enough for it to break down though ...

Odysseus sounded great but Anthony Michaelson wouldn't listen to me about the issues with cheap under-rated parts in it and rejected my internal report on the matter... After he'd asked me to write it... virtually all of them blew up within a few months of being sold! Tim re-released the design under his EAR brand and with all the issues sorted ;)

[anthonyTD]

:)
We were already in agreement over UL of course.... :)
I have an original copy of the GEC amplifiers pamphlet that I ordered from the factory when I was about 13!

[anthonyTD]

From what I remembered at the time, the original control grid was strapped to the Cathode, and the Screen grid was then used as the control grid!
'Enhanced Triode Mode' (whatever that is - maybe some variant of ultralinear?) and a custom 'quadrafillar' output transformer. I have to say its performance with my current-hungry Tannoys was pretty outstanding even with a meagre 32 watts, pretty close to what my PP KT88-specced (KT90-equipped) Radford STA100 manages.

[Reffc]

Some oddball designs by Time de Paravicini fall in this category as well .. EAR 861, push pull EL519s, no global negative feedback, supposedly pure Class A (presumably up to the distortion specs at least), uses 'Enhanced Triode Mode' (whatever that is - maybe some variant of ultralinear?) and a custom 'quadrafillar' output transformer. I have to say its performance with my current-hungry Tannoys was pretty outstanding even with a meagre 32 watts, pretty close to what my PP KT88-specced (KT90-equipped) Radford STA100 manages.


You'll find Tom that your RFC Canterburys aren't actually that power hungry and won't draw a lot of current at all, even at modest to loud listening. Minimum impedance is 7.4 Ohms at low frequency and they're nominally a true 8 Ohm load with a sensitivity approaching 92dB/1w/1m at 1KHz, and slightly more, about 93dB/1w/1m at cab tuning (low frequency). The worst case phase angle is around -42 degrees at 60Hz but as impedance is close on 12 Ohm at that frequency, it's not that demanding a swing in terms of current. A good 25 Watt PP valve amp, or a 20w to 30w SE amp using a little global negative feedback will drive them no problem at all. 35 to 40 Watts PP is better. Even a 10wpc SE amp will drive them to pretty loud levels but just wont provide the control or dynamic swings of something with more power and lower output impedance. A modest valve amp like that wont provide the concert-hall dynamics you get with your monster Radford though!

I will be treated to a TRON Atlantic SE amp in the system just for a bake-off of various components with Graham in the not too distant future, so it will be interesting to hear just what 10 Watts of pure class A loveliness can do with them!