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

Very good points yaluaka.  Every component choice involves some kind of tradeoff, and if low-powered SET is your thing, you either live with some compromise on ultimate volume capability or a MUCH more limited range of speaker choices.  The right sonic choice depends on a wide range of variables and one should not limit the candidates by the type of tube, or for that matter the topology--single ended triode is NOT inherently better sounding than pushpull or output transformereless, etc.  I own a parallel single ended 2a3 amp, a pushpull 45 amp, and a pushpull 349 amp.  The parallel single ended 2a3 is, by far, the most expensive and it is terrific sounding, but, to my taste and in my particular system, the pushpull  349 is the best overall.  If I had to pick the best amp I've ever heard, it would be a custom built OTL amp or the Western Electric 59B amp (pushpull 252 tube that is an ultra rare and expensive tube similar to a 300b).

After hearing many amps employing these tube types, I do come away with some very general observations about tendencies, although there are many exceptions.  The 2A3 tends to be leaner sounding (not as much warmth and upper bass) than the 300b, which also means it has a clearer sound and it has very good dynamics and has tighter bass as compared to a 300b.  The 45 is very nicely balanced and has tight bass, and sort of lies between the 2a3 and 300b in terms of midrange warmth.  There is something "beautiful" about the midrange for the 300b.  It has a very warm, comforting sound, but, it does not have quite the dynamics and lively sound as the other two types.  I've heard pushpull amps that are very similar, by the same builder, employing all three types, and these rough characterizations come through.  No particular sound is "better" and much depends on the speakers being use, the room acoustics, etc.  

+1 for Aric Audio

Give Aric Kimball a call, he's a great call even if you don't buy his equipment. He offers 2 different 300B amps, a 2A3 amp, an EL34 "Push Pull" amp, a KT88 "Single Ended", and a pair of KT monoblocks. I own his Motherlode XL preamp, and the EL34 "Push Pull", and they are ridiculously good with high end components.

Ralphs (Atmasphere) tube amps get great reviews (though I've not heard them), and would be a great option for OTL amps. He even suggested that you look at the below Raven monoblocks.....tells me a lot about his honesty.

The Don Sachs/Lynn Olson Raven monoblocks that Ralph suggested, are Don and Lynn's end game amps.....though end game costs $10,000 for each monoblock

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.

Hey Atam,

you’re entirely right, I have push pull amps too and love them. But that’s not my point. The 300b/2A3/45/50 tube world is a culture unto itself. And I find that huge fun to be a part of. Not only do they (or I should say, they can) sound great, but it’s a very interesting esoteric part of this hobby that’s great fun to learn about, historically both from hifis inception and more recently with Japanese and other Asian cultural approach’s to this era of equipment design. 

It has been a while, but, I have heard the Atmasphere M 60 and M 30 amps.  I liked the sound a lot--very alive and vivid without being harsh.  If you are looking for extra warmth, they might not be ideal, but, they are still very fun to listen to.  More recently (about three months ago) I got to hear their MA 2 (I believe) amp which is much bigger and it sounded great.  Some SET amps are also very lively and dynamic sounding within their restricted output, but, OTLs do the extreme dynamics too and should certainly be under consideration for a tube-based system.