300B / 845 SET amplifier

[Filterlab]

As my love for valves and Class-A continues, I find myself drawn to trying an SET power amp, or ideally monoblocks. I would never get rid of my current buffer and amp of course, but it's nice to chop components around for fun. My speakers are very sensitive so low power is not a problem.

I read great things about the 300B and 845 based power amplifiers, so tell me about your experiences.

[Opti-cal]

SET's are, for me, as intimate a musical experience that I've found so far. With efficient (usually horn loaded) speakers they convey music like no other configuration. I started, like many, with some cheap offerings from China (EL34 based amp) but I have to say even they were impressive. I got lucky and paired them with some Loth X BS1 speakers (which I own to this day) and the combination was instantly spellbinding.

I was given some very good advice regarding tube upgrades which made things even better. Also having a fully tube rectified power supply made a big difference for me. Transformer quality also plays a vital role (as ever) and if you can stretch hand wired point to point retains the purity of signal which is their trump card.

Some, especially the cheaper ones, can fall apart with more complicated passages of music and they do tend to flatter acoustic/jazz/vocals but I've managed to get them to sound lively with all genres partnering them with subs for a full range performance.

I've actually got a very high spec 300b being customised at the moment (300b for me is where it's at but 2A3 is awesome too, just a different "flavour", not tried an 845) I literally cannot wait to get it back.

I think at some point everyone should try a SET. I can see how they might not be to everyone's taste but if you favour engrossing musicality over sheer dynamics and scale it's a glorious experience when partnered correctly.

Go for it!

[Pigmy Pony]

My Audion Silver Night 300b Stereo power amp is currently enjoying a holiday from my system - pity you don't live nearer, you'd be welcome to borrow it.

It does a lot of things well - I like the sense of 'air' around the vocals, and on simpler material it is wonderful. Just seems to get a bit flustered with anything loud or busy. I'm currently using my Musical Fidelity A5 integrated, and my speakers, though sensitive, are liking the extra clout. I'll keep using it through the summer then swap back, and maybe decide what to stick with. Though really I'm so cloth eared I'd be happy with either :)

[Clive]

I've used 300B SE, EL34 PP, EL84 PP & SE, KT88,2A3, class D, solidstate class A/B solidstate class A SE. In my view the quality of results come down the power amp/speaker pairing. My 100db sensitivity OBs which are supported by active bass below 100Hz are ideal for low-powered amps. I always end up returning to my 300B amps with these speakers. In another system with easy to drive speakers but with 86db sensitivity - I use class D clarity to "wake them up". Most amps can shine but often only with speakers which gel with them. I echo the earlier comment about 2A3.

[Filterlab]

So, some positive things there! I have seen the ANK Legend monoblocks which I quite fancy building, but for the cash I'd rather get something ready-built. What sort of thing around the used £4K mark would be worth pursuing?

[Ali Tait]

300b are difficult to drive properly, it's not until you hear an amp that does so that you realise what's missing from most others. If I was looking for a 300b amp I'd be asking Nick Gorham to build me one.

[Opti-cal]

Ali is right, no point in messing about with inferior incarnations. C3M driver tubes seem to be a very good match with them, although I'd like to hear what a C3G could do (superior version of C3M).

You shouldn't struggle for that budget at all though. If you do go a tube rectified power supply route I can thoroughly recommend getting either a NOS RCA 5U4G or Svetlana Winged 'C' rectifier, they just sound better with the right amount of 'sag' for some very special tube moments. Also could shoot for a GZ34/5AR4 rectifier taking into account that the 5U4G is directly heated (no cathode) and the GZ34 is indirectly heated (cathode). (Something for your builder should you go that route). NOS Mullard/Philips would see you right in this department.

Output tubes would always be Gold Lion PX300B for me. They are about the best of the "less than a house deposit" 300B's. Although I like the EH 300B's too. (I think they are from the same factory and the Gold Lion's are 'selected'). Of course if you're feeling flush there are options to drop over half that budget on just a pair of output tubes, but I really cannot give any advice on doing so as I've never heard them, (probably a good thing).

[Macca]

300b are difficult to drive properly, it's not until you hear an amp that does so that you realise what's missing from most others. If I was looking for a 300b amp I'd be asking Nick Gorham to build me one.

Yes. That one he built for Gaz was the only 300B I've heard that lived up to the hype.

[Ali Tait]

Yes agreed, best 300b I've heard yet.

[JohnJo]

And it looked awesome!

[AJSki2fly]

As my love for valves and Class-A continues, I find myself drawn to trying an SET power amp, or ideally monoblocks. I would never get rid of my current buffer and amp of course, but it's nice to chop components around for fun. My speakers are very sensitive so low power is not a problem.

I read great things about the 300B and 845 based power amplifiers, so tell me about your experiences.

I previously had a pair of Renaissance RA01 300Bs, an interesting design based on SET design but as I understand it with an element of Push/Pull, they produced about 18w and were extremely good, very natural sounding, with a purity of voice(if you get my meaning). RA01s are highly respected amps and cost new around £8.5K, and are very well engineered, I understand they can still be built to order. I changed them for an Allnic T1500 mkII 300B SETabout 2 years ago, mainly to go to fewer boxes, as it is a stereo integrated, but I suspect that really there is minimal in terms of pre-amp. I would say the difference between them is minimal and hardly worth mentioning. The RA01's maybe had more bottom end but that is being very critical, the Allnic has a lovely presentation, maybe very slightly sweeter in the top end but again very subjective. I do know of an available VG pair of RA01s if you fancy a try.

By the way I love the Allnic T1500, truly a hidden gem of an amp, its not cheap as 300Bs go but it will easily stand up next to some gear costing 3 or 4 times the price, it has great bottom end control and grunt, a friend of mine drives a pair of Tannoy Kensington GR's with one and it sings as do my WB Vector's. Allnic's T2000 is supposed to be awesome and their AllNIC M2500 PX25 20w / 300B 30w / KT150 100w, MONO AMPLIFIER(3 configurations available) are reported as the last amps you are likely to ever buy (I would have a big problem justifying these to her indoors).

[Filterlab]

Thanks chaps for all the input. I'm teetering on a pair of Allnic A5000 Neo monoblocks - but requires a budget rise. I also like what I read about the various Audion 300b incarnations. Choices choices! :lol:

[Pigmy Pony]

Thanks chaps for all the input. I'm teetering on a pair of Allnic A5000 Neo monoblocks - but requires a budget rise. I also like what I read about the various Audion 300b incarnations. Choices choices! :lol:

Well I do like my Audion Silver Night 300b, but before deciding either way, have a word with Alan Firebottle as he has been inside mine (ooh-err) and can probably tell you more about their construction. Audion do a higher spec 300b, called a "Golden Night" I think. Don't know anything about it.

[AJSki2fly]

Thanks chaps for all the input. I'm teetering on a pair of Allnic A5000 Neo monoblocks - but requires a budget rise. I also like what I read about the various Audion 300b incarnations. Choices choices! :lol:

I think you will find them a sonic game changer, if only I could afford a pair:scratch:

[Pigmy Pony]

Allnic gear will be in another league entirely, but quality like that don't come cheap :)

[Filterlab]

No, the pair I've seen are nigh on seven grand, quality gear though.

I saw the Audion Golden Night - very nice, in the same league as the Allnic A5000 Neo I'd imagine.

[Marco]

Why did you not post this originally in Blank Canvas, daftee?:D

It's only discussions about valves themselves that go into The Artist's Palette. If it involves an amp, and it's currently available, then BC is its home. If it's vintage gear, then it goes into Past Masters.

Shimples, innit?;)

Marco.

[Filterlab]

Cos it's got valves, so it goes in the valves discussion.

Shimples times Infinity (no come backs). :D

[Marco]

Lolz... Ok, just this time then dahling, since yoor sho shexy:eyebrows:

Marco.

[Filterlab]

Mwah!

Happy where it is. :)

[AD Audio]

Hi Rob,
SE rocks indeed (and does every other form of music very well too!) As you might imagine I've had all sorts of exotic 300b SE amps through my workshop from Shindo D'Yquems, to other Japanese, UK, and US exotica. Yet the SE amps I've chosen for my home use are not 300b driven but use 845 and 805 output tubes. Why? Because these amps have decent outputs of circa 50 watts and bash out the frequency extremes with much more realism than a 300b can manage without losing anything in the mid range. In the lounge I've got Mastersound 845 PSE monoblocks, while in my studio I've got modded Ming Da 3008 Cavatinas with 805 tubes. If I were you, as indeed I did, I'd score myself a pair of Ming Da Cavatinas new around £4k or secondhand around £2k and even without a few judicious mods you've got a great performing amp. To my ears, the 805 tube is the great unspoken find, giving around 50 watts per single output tube and more inner music insight than an 845 or 300b. There's enough grunt and drive for any sensible speakers and believe me either of these amps provides massive scale and dynamics that no 300b or 2A3 could ever match. The 805 Cavatina uses 300bs as driver tubes so in fact you do get that 300b magic along with all the benefits of the 805.

You're not going to get valve rectification for these output tubes but as I've proven the difference between properly designed solid state rectification and tube rectification cannot be identified in A/B testing when voltage is matched. Changing to solid state rectification is quite a common mod now the real classy rectifiers such as GZ34 are getting so expensive. You're very welcome to a listen of down this way
David

[Filterlab]

Wow, thanks David for the advice and the offer. I'd not even heard of 805 valves so I'll have a scan around and see what I can find and listen to. :)

[dowser]

Don’t discount 211 or GM75 designs either, deliver a reliable 20-25W and match ESLs perfectly.

[bumpy]

As my love for valves and Class-A continues, I find myself drawn to trying an SET power amp, or ideally monoblocks.

I have difficulty in seeing why monoblocks have an advantage. Sure, you separate left and right channels, but at a cost of two lots of casework etc. For the same money you could by a stereo amp with much higher quality components and perhaps even better sound than the monoblocks.

Just throwing it out there.:)

[Filterlab]

Shorter speaker cables is the primary reason, then flexibility in positioning on racks etc., then easy adjustability for level control (if by some chance there's an imbalance), then complete lack of crosstalk and potential interference.

But there is a price to pay for that of course.

My current power amp is a dual mono in one chassis and I probably wouldn't notice a difference if it was the monoblocks version. :)

[Barry]

I'm a great believer in monoblock amps for the same reasons Rob has listed.

I have mine located directly behind each speaker, so the speaker cables are less than 1m in length (and could, with some rearrangement of amplifier position, be only 15cm long). The monoblocks are connected to the preamplifier (a true dual-differential balanced design), via blalanced line cables which run under the floor back to the preamp and sources.

[Macca]

But how long would the speaker cables need to be before the resistance got high enough to actually gave audible degradation? 100 metres? 200 metres?

I use 3 metre lengths, I can guarantee if I reduced that to 1 metre lengths it wouldn't make any difference to the sound.

[Opti-cal]

Not necessarily doing it just for the change in impedance/resistance of a long run, but if you are a 'cable guy' (and I am to a certain extent) you then only need 1m per side instead of 5 . . . . which for some cables will cover the increased cost of going the mono-block route.

Regardless of SQ it can make economic sense (although possibly not for the vast majority).

[Filterlab]

Not necessarily doing it just for the change in impedance/resistance of a long run, but if you are a 'cable guy' (and I am to a certain extent) you then only need 1m per side instead of 5 . . . . which for some cables will cover the increased cost of going the mono-block route.

Or allow one to get a cable which is 5x the price for the same cash. Whether it would be five times better is questionable, but that's the law of diminishing returns for you. :lol:

[bumpy]

You still need to get (longer) interconnects from the pre amp to the power mono blocks. So is the premise here that speaker cables have more influence on both cost and sound quality?

[Opti-cal]

You still need to get (longer) interconnects from the pre amp to the power mono blocks. So is the premise here that speaker cables have more influence on both cost and sound quality?

If the longer runs of interconnects are balanced I would guess yes. Like all things hifi, it probably depends. The differences between cheap (relative) and expensive balanced interconnects are less easily discernible to me than differences between unbalanced interconnects and indeed speaker cable. Different types/materials will work better in some systems than others.

Back to the sub-plot somewhat, I think Barry has concluded that by using balanced interconnects for the long run of cable needed to physically reach the amplifiers, it makes more sense to have this (low level) signal balanced than having the same long run of 'signal' carried over the same distance at speaker level power. Maybe.

[Filterlab]

I'd agree. My system is fully balanced and changing the balanced cables has made less difference than changing the speaker cable. I've also found that a higher price doesn't necessarily mean higher quality with balanced cables. I've set upon Chord Clearways throughout. I've tried a few much more expensive and they were noticeably worse in my system.

It's a strange old game!

[Opti-cal]

Another aspect to consider is that a lot of tube power amps are not true balanced inputs. They may have balanced inputs but often they are just wired to accept XLR input for convenience. Making the circuit fully balanced is pretty complex as the components are inverted/non inverted I can't quite remember. I don't have much knowledge on the subject but a quick search did suggest:

The only confirmed manufacturers of new tube amps which are balanced are Mcintosh, Rogue Audio, Cary Audio, Atma-Sphere, ARC and VTL.

There's probably a few more but if you're getting a custom built it could certainly be factored in.

[Opti-cal]

I'd agree. My system is fully balanced and changing the balanced cables has made less difference than changing the speaker cable. I've also found that a higher price doesn't necessarily mean higher quality with balanced cables. I've set upon Chord Clearways throughout. I've tried a few much more expensive and they were noticeably worse in my system.

It's a strange old game!

Sorry for thread derailment (but as it's your thread!) I've just ordered a pair of these.

https://www.aliexpress.com/item/4000993616933.html?spm=a2g0s.9042311.0.0.22ac4c4dd S2eYv

They tick a lot of boxes for me. 6N OCC copper cable with copper XLR plugs. Should be the business for the price. I really like the Chord Clearway range too actually, decent value. There are a lot of chord haters but their mid range stuff always does a good job for me.

[Barry]

Back to the sub-plot somewhat, I think Barry has concluded that by using balanced interconnects for the long run of cable needed to physically reach the amplifiers, it makes more sense to have this (low level) signal balanced than having the same long run of 'signal' carried over the same distance at speaker level power. Maybe.

Yes, that is exactly my thinking. Before the current set up, I had to use two different length speaker leads, roughly 6m and 16m in length. These had a loop resistance of 0.104 Ohm and 0.202 Ohm respectively, meaning the damping factor into an 8 Ohm load was 77 and 40. The output impedance of the amp was only 0.02 Ohm. The loop resistance and inductance of any speaker cable, regardless of length, ideally ought to be no more than 0.1 Ohm + 3uH.

The general rule of thumb is for the loop restistance to be no more than 5% of the nominal speaker impedance, which if assumed to be 10 Ohm, is 0.5Ohm, giving a damping factor of no more than 20. However, depending on the variation of the speaker's impedance with frequency, a series 0.5 Ohm esistance can exacerbate the variation in frequency response by up to 1dB, which may be audible.


Audible differences between different balanced interconnects are far, far less than those between different unbalanced cables, for the simple reason there is no duplication of the shield (screen) to act as signal return and safety earth. That is one of the reasons why balanced lines are used in professional broadcast and recording studios. One further advantage IMO, is the avoidance of the awful RCA phono connector through the use of XLR connectors.

[Filterlab]

There are a lot of chord haters but their mid range stuff always does a good job for me.

Same here. I have Chameleons in my second system (unbalanced) and they're excellent bits of wire which are a bargain price.

Both those and the Clearways just seem to be completely even, favouring no particular frequency range. Well thought out wiry bits.

[Filterlab]

Audible differences between different balanced interconnects are far, far less than those between different unbalanced cables, for the simple reason there is no duplication of the shield (screen) to act as signal return and safety earth. That is one of the reasons why balanced lines are used in professional broadcast and recording studios. One further advantage IMO, is the avoidance of the awful RCA phono connector through the use of XLR connectors.

When I did pro audio everything was balanced. One could have a tangle of cables running all over the place, past power points and power amps, with nary a hum. Just so easy to get a good signal.

[dowser]

I have difficulty in seeing why monoblocks have an advantage. Sure, you separate left and right channels, but at a cost of two lots of casework etc. For the same money you could by a stereo amp with much higher quality components and perhaps even better sound than the monoblocks.

Just throwing it out there.:)

Simple for me - I wouldn’t be able to move it by myself if it was integrated, and it would be huge!