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Joe
10-10-2009, 19:17
OK, so I know there's the above two types of valve power amps. What's distinctive about each in terms of sound, or does that have more to do with the competence of the designer than the configuration of the valves?

PS It's not just idle curiousity, I do have a reason for asking, but would prefer general comments and this am not mentioning specific models.

PPS Bear in mind I'm an arts graduate, so keep any explanations at the simplistic level.

Cheers

Ali Tait
10-10-2009, 19:35
What kind of sound are you looking for? In VERY general terms,the generally accepted characteristics are this-

SE-A good SE amp will beguile you with a magical mid and top,with great soundstaging,at a little expense of a deep and muscular bass.

PP-A good one will give a deeper and stronger perceived bass,but at the expense of a little of the great mid and top of an SE amp.

This question is a real can of worms,and what I have said can only be taken in very general terms.It would be best to hear both types for yourself before making your mind up.Just my 2d worth.

Marco
10-10-2009, 19:59
Hi Joe,

It's a difficult question to answer properly in a few sentences. I'd agree though with Ali's brief summary :)

What kind of sound are you after - are you in the market for a valve amp or is it just curiosity?


What's distinctive about each in terms of sound, or does that have more to do with the competence of the designer than the configuration of the valves?


That's 100% correct. The key word is *always* implementation!

Marco.

Cotlake
10-10-2009, 20:19
Hi Joe,

I endorse Ali's response but you will also want to consider the versatility you need. If you listen primarily to simplistic music such as folk, easy jazz or classical quartet type stuff, most SE amps will work very well for you. Most of them however will run out of steam with demanding stuff like heavy rock, big orchestral or dance music. In fact a couple of years ago I used a dance track on Will's SE system and it was a total mush of distortion. Please understand, that is not a critisism of Will's system which is fantastic. This is all about what you want to do and what you want to play. The further consideration is that with an SE amp you are also listening to the power supply section so you would need one where design has been optimised in that area. If you still want SE and want to play demanding music, you'll need to think in terms of amps with transmitter valves like GM70, 211, 845 etc which have a relativily high output but also soak up the current.......glowingly pretty though :smoking:

Speaker sensitivity is also an issue. Because of the limitations an SE amp has, giving it the easiest life possible is the way to go so high sensitive and easy to drive speakers are the order of the day.

I use a highly tweaked 300B PP fed into moderately (90dB) sensitive speakers. This can produce up to 36W per channel max but that level is hard on the 300B's. I have reduced this to about 31W dissipation which gives them an easier time and also gives me about 11W output in class A. I like to listen loudish and domestically I'm sure the amp remains in class A all the time. It works for me.

In contrast, Steve drives a pare of sensitive (I think around 105dB) open baffle speakers with just 2W of SE power and they work in a large room with some very challenging music, but there are compromises to be made in terms of equipment size especially speakers and what is domestically acceptable. If I had a dedicated listening room I'd not hesitate to go down the low output single ended route with appropriate speakers but that is a luxuary I can't achieve at present.

Personally, versatility is the requirement, so I'm happy to sacrifice a bit of mid-range magic for the flexibility my PP amp provides, and of course, by tweaking you do optimise the overall performance anyway.

Thereafter, it's simply a matter of listening taste. Most SE advocates continue with the design regardless of the limitations because they can't tolerate the PP sound. As Ali suggests, you probably need to suck it and see and a visit to an Owston type event would really help you on this. Be sure, however either type will sound better than any sand amp (ducks). Also remember that with sand amps, the class A option is often considered near the top sound wise, example being the Sugden 21. Expensive and hot to run just like a valve amp ;)

Hope that helps a little.

Regards,

Greg

Joe
10-10-2009, 20:24
Thanks Ali and Marco and Greg.

I'm not trying to be mysterious, really!

I have a single-ended valve power amp, which I'm happy with bar its somewhat temperamental nature. However I have the opportunity to buy a push-pull valve power amp at a favourable price that's from the same manufacturer as my pre and phono amps, and I'm just wondering about pros and cons. I doubt I'll be able to compare the two side by side before purchase, so it'd be a bit of a gamble.

In terms of sound, my current amp sounds fine as far as bass goes; it doesn't do pin-point imaging but then that's not high on my priorities list. It's good on whatever I've played on it (jazz, punk, chamber, orchestral, folk).

I suppose the bottom line is, does system synergy trump other considerations?

anthonyTD
10-10-2009, 20:44
hi all,
i agree with a lot thats already been said on this subject so far, although there is also the fact that all comercial single ended designs are inherently class A by default, therefore the most wastefull on power and valve life, with eficiency being typicaly around 22%! where as push-pull designs can be biased from anything between class B and full on class A making it posible to gain up to around 60% eficiency. also concerning the diffrences and weakness of both technologies, it is posible to over-come most in both, ie, its posible to have a single ended amp with real solid bottom end as well as the rest of the qualities their well known for, equaly, it is posible to get the kind of midrange from a push-pull amp that is usualy only found in the best single ended designs, its all about the topology and implementation of the devices used and carefull circuit design.
regards,anthony,TD...

Steve Toy
10-10-2009, 21:36
It is a speaker/amp matching thing. Push pull on the end of super high sensitivity speakers can sound rather stodgy.

Single ended driving low sensitivity speakers sounds rather flat.

Joe
10-10-2009, 22:01
Thanks Anthony and Steven for the further responses.

Speaker sensitivity shouldn't be an issue; mine are 91db so neither inefficient or super-efficient. 'Stodgy' is a definite no-no for me though; I had enough of that when I used Castle Chester speakers. Nothing would wake those buggers up, and I tried plenty of things.

Thinks: If I dither long enough the amp will probably be sold to someone else: problem solved!

Steve Toy
10-10-2009, 23:58
I would say for 91dB a push pull would be better. You are going to need at least 25 wpc.

anthonyTD
11-10-2009, 09:47
hi joe,
91db is fine for either push-pull or single ended, what is more important with valve amps is a constant impedance through out the audio frequency range, ie; most manufacturers state a nominal impedance, this may be 4,6,8 or even 16 ohm, but what they dont always tell you is at what frequency this was measured, with some speakers [Extreme cases] the diffrence in impedance within a few hundred hz could be double or half the stated nominal figure, so, when partnering speakers to valve amps it is very usefull to study any graphs that may be available from the manufacturer, this will tell you lot about whether the speakers will present a good load for a valve amp.
hope this helps.
regards,anthony,TD...

Giant Haystacks
11-10-2009, 09:48
a very big part of good single ended sound is the acoustic bass which has a freedom not as big a bass as push pull , but you are limited to 5 watts there is a valve called a type 50 which there is still new old stock of still only 7 to 8 watts , a 211 amp or 845 amp will be expensive .i have a 5 watt amp and i have 10 diffarent makes of output valves for it and they sound diffarent

Joe
11-10-2009, 10:41
hi joe,
91db is fine for either push-pull or single ended, what is more important with valve amps is a constant impedance through out the audio frequency range, ie; most manufacturers state a nominal impedance, this may be 4,6,8 or even 16 ohm, but what they dont always tell you is at what frequency this was measured, with some speakers [Extreme cases] the diffrence in impedance within a few hundred hz could be double or half the stated nominal figure, so, when partnering speakers to valve amps it is very usefull to study any graphs that may be available from the manufacturer, this will tell you lot about whether the speakers will present a good load for a valve amp.
hope this helps.
regards,anthony,TD...

Thanks, Anthony. The speakers are a nominal 8 ohm, but beyond that, technical information is hard to come by. Certainly they sound loud enough at 'quarter to' on the pre-amp volume (I've never dared go beyond 'ten to'!) and the reviews I've read describe them as an easy load and thus suitable for low-powered valve amps. It doesn't help that they are made in Denmark and no longer have a UK distributor, but I'll contact the manufacturer and ask if they have the info you mention.

anthonyTD
11-10-2009, 11:06
hi joe,
your welcome, i will elaborate a bit further if i may as to why this is so important... either side of the optimum impedance, a valve amp will give less power, so for example if a speaker had a nominal impedance of 8 ohm at 1khz which was an ideal load for the valve amp being used, if it then raised to 12 ohm at say,,,3k, then you have a drop in power compared to the nominal , same thing the other way if the speaker impedance drops at say 500hz to 4 ohm. i must stress that speaker impedances can rise or fall at any paticular frequency depending on their design and the above is just an example and must be taken as that. on the other hand transistor or solid state amps will to a point give more power into a lower load than a higher one, thus why a speaker on a solid state amp can have a totaly diffrent presentation than on a valve amp, so with that,,,it can be seen that it is important on both types of technology to keep a speaker's impedance as constant as posible.
regards,anthony,TD...

Ali Tait
11-10-2009, 15:18
Good stuff said by all.I think a lot of the percieved weakness of SE in the bass is down to the nasty load presented to these types of amp by most commercial speakers,and not necessarily down to the design topology.

anthonyTD
11-10-2009, 18:13
Good stuff said by all.I think a lot of the percieved weakness of SE in the bass is down to the nasty load presented to these types of amp by most commercial speakers,and not necessarily down to the design topology.
agreed!:)
A...