300B or 2a3 SET Class A for Heretic Model A?

Due to the good impedance and DB of my new speakers, how would compare a proper SET 300B Class A to small EL84/34 based tube integrated such as Leben CS-300Xs, Luxman SQ-N150, Mastersound Dueundici, etc.

@superelmar That will depend on how well the designers understand how distortion affects what we perceive. You'll have to try them and see. But if the EL84 amp is properly designed and built then I would not expect a downside compared to an SET. The tricky bit is if you mix single-ended circuits with PP in an amplifier, you get some distortions (in particular the 5th harmonic) which I have no doubt is part of the reason SET advocates are so staunchly loyal to their SETs.

That can be avoided by insuring that the PP design is fully balanced from input to output. In this way the 5th harmonic enhancement is avoided so the amp sounds smoother and more involving. Fully balanced PP amps are rare FWIW as so many 'designers' simply use legacy circuits from 1950s textbooks or prior designs, so have the same flaws baked in.  To keep the playing field level the PP amp should also be class A. 

@yaluaka I am very focused on the sound; if its right then the music is processed by the limbic portions of the brain which increases body movement and emotional response. Increased engagement.

I run a recording studio as well as manufacture amps and preamps. When the system is accurate it is also musical and engaging. IOW 'accurate' and 'musical' are not two different things. They are the same thing.

If you think otherwise it is because you've only encountered equipment that was claimed to be 'accurate' but was not (and was amusical; far too much of that out there) similarly the 'musical' equipment you've heard apparently was not as musical as is possible because it could not also be true to the music (accurate) at the same time.

Now I get that you can use R2R tape to warm up a digital recording (because it adds a 3rd harmonic) or run it through a single-ended tube circuit to add a 2nd harmonic; I understand how distortion affects our perception of musical (keeping in mind that understanding that is important for the design side of my work).

What I'm saying here is the distortion signature of any amp is paramount to how it sounds- the distortion signature is its sonic signature. So obviously the distortion signature must be as benign as possible (lower ordered harmonics dominant as seen in an SET or our class D or our OTLs) but also as low as possible so the equipment can reproduce low level detail properly.

To me this is also a specious point, the idea of accuracy in recorded reproduction. I’m looking for something I like. I don’t want a stereo limited by only sounding good with any particular music or record label. It’s not about accuracy, to me accuracy is anti musical. I want the music I listen to- to be engaging. Accurate is irrelevant, in fact I don’t think it exists. Perhaps an extreme view point. You get into set amps because you want to experience the music not judge the recording.

@yaluaka It appears to me that you are conflating ’accurate’ with ’anti musical’ as emphasized above. That isn’t how its supposed to work; if the amp isn’t musical its also isn’t accurate. IOW if you want the most engaging presentation, the amp will be both musical and accurate. That exists. When the amp is musical but not accurate (as is the case with most SETs) then while it might be engaging, its not as engaging as it could be, because you’re really not hearing the music properly.

For some decades now the solid state community has beat up on tubes by saying that solid state is more accurate. But most of the time those amps were not musical because they made distortion to which the ear is keenly attuned. So those amps had ’low distortion’ but sounded harsh and bright- not at all engaging.

As a designer, once you understand how the ear perceives sound and how that relates to distortion amps make, you can design an amplifier that is both accurate and musically engaging. If you really understand how this works, it doesn’t even have to be a tube amp; the ’sonic signature’ of any amplifier is also its distortion signature. So if you can get a solid state amp to have the same sort of distortion as a tube amp, it will sound like a tube amp. That’s only one of the implications of understanding how this all works.

Put yet another way, there are tube amps that are more engaging than the best SETs, with wider bandwidth (read: more and deeper bass impact) and greater power at the same time.

Its not about judging the recording so much as it is enjoying the music. We’re on the same page with that. It sounds to me as if you’ve been exposed to too many amusical amps that were purported as ’accurate’ when they were not. Harsh and bright to me a far more egregious coloration than the ever-lovin’ 2nd harmonic of tube amps. But if you can get that 2nd harmonic down, you can get more detail, since distortion obscures detail. And you can do this without it being bright.

 I also agree with the poster who said running low powered SETs gets you entrance to a cult, and it’s one where you can land on some magical combinations of speakers and amps. 
It’s all fun, so long as you don’t mind losing your eyebrows every once in a while.

Its really about SETs being a musical instrument rather than a music reproducer. Fun, but its not at all accurate to the recording. That profound ever-lovin' 2nd harmonic gets a richness that isn't part of the original recording; that is why I say 'musical instrument'.

It always bothers me when some asks about a lower power tube amp and someone chimes in with, get a higher powered amp. To me if you want a 300b, 2A3 or 45 amp get one. I have all three. I listen to music all day and at good volume and one room is 1400 square feet. These amps are the best, and at the same time there is a culture around them. The people who espouse the more power mantra are not part of that culture and are irrelevant if you really want a low powered tube amp that’s about sweetness and musicality and tactile-ness.

@yaluaka I've tried plenty of SETs over the last 30 years as well as designed and built my own using the 45, 2A3 and 300bs. SETs do not rule the roost in any of the areas you mention above. But there are plenty of PP tube amps that fall short; if you've not been exposed to the right PP amps I can easily see how you came to your conclusion.

Here are some things to consider: The mark of the best systems is they never sound loud even when they are. You may have noticed that your SETs seem to get plenty loud but what is happening is the distortion they make causes them to seem louder than they are (there are sound pressure apps for smartphones that can easily show what is happening). When you have an amplifier with less distortion it will be very natural to use more power and enjoy it.

The distortion of SETs increases linearly as you increase the power level. Above about 20-25% of full power, the higher ordered harmonics start to show up. They appear on transients (where the power is) and because the ear uses higher ordered harmonics to tell how loud a sound is, this causes the transients to sound louder, giving the amp a very 'dynamic' quality.

IOW the dynamics of SETs is really distortion and nothing more- real dynamics come from the music.

Bandwidth is another problem; with greater power its progressively harder to make an output transformer that really has hifi bandwidth. So usually the highs are made right and the bass suffers, since the kind of speaker you need to really take advantage of an SET (likely horns) often don't have deep bass response. So if you really want to experience the music properly you'll need subs and driven by the preamp rather than the amps.

OTOH, there are PP amps that are every bit as involving that don't have  these problems. Consider though that if you really want to compare apples to apples, the PP amp might have to use the same kind of output tubes, perhaps it should also be class A and zero feedback as well, to level the playing field? Usually these things aren't considered when making comparisons. You might also consider what happens if the PP amp makes the same power as the SET; for example if compared to a 2A3, perhaps the PP amps only makes 5 Watts? Again, to level the playing field.

If you work to eliminate these variables you find that SETs really don't have an sonic advantage over a well designed and built PP amp.

Well are 100db if that doesn’t work for 45…

@superelmar exactly! You need about 6-7 dB more; type 45 amps are better suited for headphones.

@superelmar A lot depends on your room size. When you are using SETs, if you run them past about 20-25% of full power they tend to make more higher ordered harmonics, which, since the power is usually on transients, tends to make the amp sound more 'dynamic'. This is because the ear uses higher ordered harmonics to tell how loud sounds are.

So a typical 300b amp might make about 7 Watts, but it really has a bit less then 2 Watts that are really usable (if you want to hear what the amp can really do).

So my recommendation is to consider an amp with more power. My speakers are 98dB; 2 dB less than yours and my room is not particularly large. I run amps with about 50 Watts; they are loafing most of the time which makes for much lower distortion so greater transparency and smoother sound.

If you are really stuck on using 300bs or 2A3 class A amps, consider something push-pull as they have much higher amounts of usable power, 90% instead of only 20%, owing to far less distortion.

Here's an example of what you might consider:

Raven monoblock

Something else to consider is there are now class D amps that are just as smooth, revealing and involving as the best tube amps.