Single-ended triode amps

[manisandher]

I suspect this post will ruffle a few feathers, but here goes anyway...

I bought a new (actually used, but new to me) pair of single-ended mono valve amps (a pair of Consonance 211S monos). They were virtually brand new and going for just a 1/3 of (not off!) their original retail price. And their reviews were very interesting. So I bought them, with no real idea of what I was going to do with them. (Not the first time this has happened...)

The seller suggested that I get hold of a pair of new Elrog 211 valves for them if possible and I managed to do this.

The amps are rated at around 15W into 8 Ohms. The speakers in my office are rated at 96dB/W@1m, although I suspect this is a little bit optimistic. In any event, I attached the amps and was literally blown away with the sound. And this only a few days after the Mach II was installed here. I could have lived with this sound forever. Really.

But then I thought... I wonder how they'd sound driving the 118dB/W@1m Orelo speakers. I knew they'd be too noisy for a permanent setup, but wanted to try temporarily anyway. So I connected them and switched them on. Immediately there was way more background noise than normal, to the point where I could actually hear the audio PC electrical noise coming through the horns - lots of clicking and swirling going on. And there was quite a bit of noise coming through the LF drivers too. At the listening position the noise remained easily audible and way more than would be ordinarily acceptable. I was going to simply disconnect the amps, but thought I'd try them anyway. I set XX to -30dB and pressed play, and...

... I was presented with simply the best sound I've ever had in my listening room. The sound easily bettered the speakers' built-in amps in every way imaginable. The only area that sounded pretty similar was the relatively lean and a bit dull/flat bass - totally different to when the amps were in my office. (But this isn't so surprising, as the bass amps in the speakers take the signal and amplify it to match the sensitivity of the mid/high horn. If they weren't there, I suspect the bass would have been a lot better.)

Reverting back to the regular all active set up, the sound is as flat as a pancake in comparison. All the magic has gone.

So, what to conclude? A few things:

1. Ambient noise makes no difference to the SQ. I know Peter will hate this statement. It's been my 'dogma' (and many others here too, I know) for many, many years. But this experience tells me otherwise. Maybe the type of ambient noise is more important than the amount. The relatively high noise coming through the Orelos from the SETs would not have been correlated with any signal. I wonder if this makes a difference?

2. The SET crowd really aren't mad. I suspect they've known all along that they have the best sound, and laugh at the rest of us. Unfortunately, most of the SET crowd use turntables (I certainly have nothing against that) and have never heard anything approaching the quality of the XX/MachII/NOS1a combination. For me, this digital chain and a SET driving a good high-efficiency horn is a match made in heaven.

3. I remember reading a paper by Nelson Pass, talking about the monotonicity of air, and how single-ended amplification is the only type that can ever truly sound 'natural' to the human ear. Maybe he's on to something?

4. I remember reading a paper by Thorsten Loesch talking about the harmonic distortion produced by a single-ended amp being benign to the human ear. Maybe he's onto something?

5. I remember reading a paper by Eduardo B. E. de Lima talking about how the distortion spectrum of a single-ended amp could actually be used to reduce the distortion inherent in speaker drivers. Maybe he's onto something?

5. With the SET in place, even with all that background noise, I could easily hear minute differences in SFS, etc. Actually, such differences were easier to hear with the SET in place. And the amount of inner detail coming from the music was nothing like I'd ever heard in my room before. The difference between the Mach II and my previous audio PC was much greater with the SET in place than with the active amps.

*********************
As a result of this little impulsive buy, I've had to reset my whole audio thinking. These amps are gems. But I suspect all decent SETs are, because of the physics of sound and the way the ear hears it...

Anyway, no going back for me! There will be a permanent SET setup in my office and in my main room by the end of the year. I cannot listen to anything else now.

Mani.

[fralippo]

SET DHT amps are the best. But good luck finding a really top quality one ;-)

[manisandher]

I know a guy who's got a massive Kondo collection. Maybe I can persuade him to sell me a pair of his cheaper monos. Would still be too expensive for me 

No, I know exactly where a pair of SETs for my main system are coming from. I've been in touch with the manufacturer and he's looking to get me a pair by the end of November. Of course I'll post all the details in due course.

Mani.

[PeterSt]

1. Ambient noise makes no difference to the SQ. I know Peter will hate this statement.

Haha, first is correct, latter is wrong.
I don't care a hoot about ambient noise and thinking twice you'll know about my kitchen endeavours.
Point is : what you call ambient noise was electrical noise first.

So what you're saying is that this noise at 60dB down (or maybe a bit more down) and which eats half of your digital bits, sounds better to you. Well, this is fine of course.
But best would be really when we could figure out that those eaten bits better be chopped off in the first place; only then it is really justified (read : at this moment they are harmful so they better not be there).
Of course it is allowed to claim that the amp still sounds better, despite that noise (so it is overly good). No problems with that one.

Regards,
Peter

PS: Just saying () : flat as a pancake is 10586.0. I (re)tried it yesterday and couldn't listen to it for exactly that reason. I can also tell you that some like 10586.0 explicitly for that so YMMV; it could give a kind of accuracy because of undecompressed depth (same as too wide and then getting inaccurate).

[manisandher]

So what you're saying is that this noise at 60dB down (or maybe a bit more down) and which eats half of your digital bits, sounds better to you.

Yes! And that even with this noise, I can hear minute differences in SFS. I didn't realise these SFS differences sat between the MSB and LSB 

Mani.

[PeterSt]

I didn't realise these SFS differences sat between the MSB and LSB 

Is there more outside of this universe ?
(I really don't understand)

[Nick]

Mani hi,

Interesting, I do like the sound of SETs so I can understand what your describing Mani.

Just a thought. Looking on line the Consonance 211 it has an input impedance of 100k, a typically high for valve input stage.

Peter is getting great sound with the NOS1 => B'ASS line buffer. => Orelos. Might some of the magic you are hearing be down to the Consonance presenting a relatively easily driven load to the NOS1 output stage ?

I don't know the input impedance of the Orelos and how they compare in this respect to the 100k input of the Consonance amps but could be using a B'ASS might make the Orelos amps closer to the Consonance, that is if NOS1 to amp matching is a factor.

I know I really need a B'ASS to help drive the eight gainclone inputs in my amp. Maybe I should get out the audio note 300b SETs that have been under the my stairs for the last 6 years, just to see how they sound compared to the gainclone setup ...... :-)

Nick.

[Scroobius]

Interesting  -  Mani you will remember my Audio Note AN speakers you heard them here and very much liked the sound of them IIRC. When you heard them they were being driven by the Gainclone amp that I built and that is featured elsewhere on this forum.

What you did not hear was the system that used to drive the AN's prior to the GC's. It featured AN DAC an AN pre amp driving two AN mono block SET valve amps.  I had made many (very expensive) changes to the DAC, pre amp and the SET's. The mono block SET's had high spec AN output transformers, matched high spec triodes and WKZ blackgate ps caps. along with other tweaks.

I only built the Gainclone amp because I saw them discussed on this forum and did not know anything about them. When I put the completed GC amp into service I was astonished with what I heard - they were much better than the SET's (in this room). The mid range was surprisingly similar to the SET's but the top end, bass and control over the speaker was in a different class to the SET's. However I do remember the SET's having a very beguiling sound.

It was then that I invested in the NOS to drive the GC amp and never looked back.

Of course life is not that simple and it would have been interesting to hear the SET's driven by the NOS1 but that was not possible as I had to sell the SET's not least because they were freaking big and I had no where to put them. Certainly my SET's just did not have the umph to deliver sensible power and dynamics in this large room even though they were driving efficient speakers. The mid range was excellent but I have to say the GC's matched them in that respect. I have heard many SET based systems but I have to say I could not be tempted back from my experience anyway.  I would love to hear your SET amps though maybe you can change my mind!!

Cheers

Paul

[manisandher]

Hey Nick, good to hear from you after such a long time!

Might some of the magic you are hearing be down to the Consonance presenting a relatively easily driven load to the NOS1 output stage ?

Certainly a possibility. However, as I said earlier:

The only area that sounded pretty similar was the relatively lean and a bit dull/flat bass - totally different to when the amps were in my office. (But this isn't so surprising, as the bass amps in the speakers take the signal and amplify it to match the sensitivity of the mid/high horn. If they weren't there, I suspect the bass would have been a lot better.)

If the improved sound was down to the SETs providing an easier load for the NOS1a, I'd expect the LF to be massively improved too. And it just wasn't. In my office, driving the 96dB/W@1m Impulse H2 speakers, the bass is simply tremendous with the SETs. Driving the Orelos, it hardly changed at all, and certainly didn't match the improvements in the rest of the sound.

Whenever I've heard Paul's Orelino speakers, I've always said there is something wrong with the LF in my speakers. The DSP adjustments sounded impressive when I first did them, but reverting back to the original filters showed me how much better they (the originals) actually were.

Right now, I'm still inclined to think the improvement in SQ is down to the phenomenal performance of these 211 SET amps. Oh, and the >$1.5k (for a pair) Elrog 211 valves - simply stunning, compared to the Psvane 211 valves that came with the amps when I bought them.

Mani.

[manisandher]

When I put the completed GC amp into service I was astonished with what I heard - they were much better than the SET's (in this room). The mid range was surprisingly similar to the SET's but the top end, bass and control over the speaker was in a different class to the SET's. However I do remember the SET's having a very beguiling sound.

My 211 SETs actually have a very mediocre sound with the cheap Chinese valves that come standard with the amps. Most customers upgrade to the very good Chinese Psvane 211 valves, which really improve the sound of the amps. I didn't try these valves when the SETs were connected to the Orelos, but suspect there wouldn't have been such a massive improvement in SQ. There really is a quantum leap in SQ going from the Psvanes to the German Elrog 211 valves. I suspect most of the magic is happening within these valves.

Certainly my SET's just did not have the umph to deliver sensible power and dynamics in this large room even though they were driving efficient speakers. The mid range was excellent but I have to say the GC's matched them in that respect. I have heard many SET based systems but I have to say I could not be tempted back from my experience anyway.  I would love to hear your SET amps though maybe you can change my mind!!

The dynamics that I'm getting with these amps, driving either of my speakers, is simply stunning. I'm sure they'd run out of steam with the Impulses at some point, but in my main room with the Orelos, I never dared taking them louder than -21dB.

Of course, you're welcome to come and listen for yourself whenever you like!

Mani.

[CoenP]

Hoorah for the SET resurrection!

The GC amp I build long ago sounded tonally fine and precise, but could not match the sheer musicality of my ultra low power pedestrian SET amps (that is a SESPPaT: a Single Ended Small Power Pentode as Triode). As a matter of fact the SET sounded more dynamic and live (compression?).

I heard noises in the Altecs too, but most of it was in retrospect the result of an insufficiently shielded interconnect.

PS: Just saying () : flat as a pancake is 10586.0. I (re)tried it yesterday and couldn't listen to it for exactly that reason. I can also tell you that some like 10586.0 explicitly for that so YMMV; it could give a kind of accuracy because of undecompressed depth (same as too wide and then getting inaccurate).

Aha, I think I encountered this flatness the past days, I already wondered if something was wrong with my ears or setup. Dynamics and balance are ok though a bit dry. It plays tunes too.

regards, Coen

[acg]

Hi Mani,

I can confirm that it is possible for SET amps to have zero noise on high efficiency horns.  I am talking put your head in the horns and hear not  whisper.

The beauty of SET's is that their level of distortion decreases as their output decreases, so with 118dB sensitivity horns such as the Orelos will be using a tiny fraction of a watt for sane listening levels and their distortion profile may be absolutely minimal.  On the other hand SS amps can really have some problems at under 0.1W output (not saying that this is the case with Peters gainclones but making a crude generalisation).

You will probably find that a lower voltage tube than the 211 will give you even better results...in my limited experience the lower voltage tubes have more balance and nuance and are able to shift dynamically with more composure.  Tubes like the 6C33C have a low plate resistance (and 200V B+) and can consequently be made with a much lower output impedance (around 0.1R-0.2R depending on loading) and in this situation where you may end up trying to directly amplify the BD15 drivers in Peters speakers the low output impedance will certainly help.

For the horn you may even be able to run a single stage SET which is as simple an amplifier as you can build.    

Cheers,

Anthony

[manisandher]

Hoorah for the SET resurrection!

 

You will probably find that a lower voltage tube than the 211 will give you even better results...in my limited experience the lower voltage tubes have more balance and nuance and are able to shift dynamically with more composure.  Tubes like the 6C33C have a low plate resistance (and 200V B+) and can consequently be made with a much lower output impedance (around 0.1R-0.2R depending on loading) and in this situation where you may end up trying to directly amplify the BD15 drivers in Peters speakers the low output impedance will certainly help.

Thanks Anthony. I'll be exploring different options going forward, and this is really helpful. Lamm uses the 6C33C, right?

Mani.

[CoenP]

You will probably find that a lower voltage tube than the 211 will give you even better results...in my limited experience the lower voltage tubes have more balance and nuance and are able to shift dynamically with more composure.  Tubes like the 6C33C have a low plate resistance (and 200V B+) and can consequently be made with a much lower output impedance (around 0.1R-0.2R depending on loading) and in this situation where you may end up trying to directly amplify the BD15 drivers in Peters speakers the low output impedance will certainly help.

Well, kind off. I do not think the low plate impedance (= usually lower plate voltages) is key here per sé, but that this provides for a better starting point for winding the output transformer. The winding ratio for a 6c33c can be much lower than ie a 211, hence better coupling and thus a wider frequency range (more high and more low). Of cource there is more to good sound than this.

Regards, Coen

[acg]

Well, kind off. I do not think the low plate impedance (= usually lower plate voltages) is key here per sé, but that this provides for a better starting point for winding the output transformer. The winding ratio for a 6c33c can be much lower than ie a 211, hence better coupling and thus a wider frequency range (more high and more low). Of cource there is more to good sound than this.

Regards, Coen

I suggested that tube and its very low plate resistance because Mani is talking about integrating it into an existing speaker system.  I suggested bi-amping, with the 6C33C specifically for the bass channel if he did wish to go that way.  The Orelo's have been designed with a very low output impedance amplifier in mind (the gainclones), and although the DSP for the low end does muddy the waters a little in suggesting the best way forward, changing amps to a high output impedance DHT or IDHT is unlikely to get a good result in the bass in this situation because those high plate resistance tubes simply cannot be have an OPT wound for low output impedance.  Higher amplifier output impedance = more SPL output at woofer resonance which is probably going to be counter-productive in this situation.

As an example, I am about to take delivery of a custom OPT for a bass SET amplifier to drive the woofer towers that I am building.  These towers have 8 x 10" drivers per side, are wired in parallel and present a load to the amplifier of 1R.  The OPT for this channel will load the 6C33C tube to 1000R which will give me about 10watts and an amplifier output impedance of about 0.2R which results in a speaker damping factor of 5 or so, which is quite high considering this is a zero feedback single ended triode.  The Bass OPT is flat (at full power) from about 4Hz to 5kHz.

In Mani's situation I predict that the important thing metric will be the speaker damping factor and the number of watts he has to play with.  Is 10 watts enough?  I don't know...it depends on a lot of things...but if it is then a low output impedance is likely to be an important factor in SQ especially if no feedback is involved.

Regarding the low voltage tubes vs high voltage tubes...this is simply my opinion and personal preference...and is influenced by what I have heard with 211's and 845's and the like.  SET amps are so difficult to integrate perfectly into a speaker system...you need high sensitivity speakers, loads of dynamic headroom and a willingness to call the results for what they are regardless of expenditure or expectations.  Because of the well documented technical limitations in SET amps they need to be carefully paired to the speakers...most hifi systems (read low sensitivity with varying impedance loads) perhaps will sound better in some areas with a SET amp, but overall the result will probably be worse than a good SS amp.  There is a LOT more to it than being able to get enough SPL.  Find that symbiotic pairing and wow, SS does not get close (in my opinion of course).

So Mani, regarding amplifying the woofers in your speakers, whether you can go SET will depend on many things, but most importantly the power response of those BD15 drivers.  Do you know how much DSP boost is required to get that system flat to 20Hz?  That number right there will be the most important thing to consider which way forward.

Cheers,

Anthony

PS: Mani, yes I have heard the early LAMM's with the 6C33C and they did sound very pleasing in that system.  The best 6C33C that I have heard though is diy.  I am copying them myself.