SET the best?

I have a reasonably efficient speaker system  (99 db/w) which I run with a variety of low-powered tube amps.  Among such amps is an Audio Note Kageki, which is a 6.5 watt parallel single-ended amp running 2a3 output tubes.  It is a pretty good sounding example of a SET amp, yet, I would not say it is the best amp for my system and taste.  I generally prefer a pushpull 349a amp that I own that outputs 5.5 watts/channel.  Both the Kageki and my 349a amp deliver an expansive and enveloping soundfield, rich pallet of harmonics and a natural presentation without edginess or overly "etched" detail.  They differ a bit in the bass presentation.  The 349a amp is punchier and tighter in the bass, but, that bass presentation is a bit "mechanical" sounding (a sameness regardless of source material) while the Kageki sounds more varied and natural (albeit soft sounding) in the attack of bass notes.  Different strengths and weaknesses, and one is not "better" than the other.

Among the very best amps I've ever heard are a pushpull amp running the 252 tube and a one-of-a-kind output transformerless amp.  Both made my Kageki sound anemic in direct comparison.  While I really like several SET designs, I hardly think that, as a class, they outshine other tube designs.

Interesting thread, got resurrected after 10 years. If Ralph still follows it I would be interested on knowing which amps he was referring to in this comment

But the amps I use are designed to not generate any loudness cues to the human ear

Were you referring to your OTLs @at

@luisma31   Yes.

The loudness cues to which I was referring are the higher ordered harmonics- the 5th and above. The human ear uses these harmonics to sense sound pressure. But it also assigns a tonality to any distortion- the higher orders cause brightness and harshness even in tiny amounts, since the ear has to be keenly sensitive to them in order to gauge sound pressure over a 130dB range.

If you know these facts then that gives you a good idea of how to approach amplifier design. Since the ear is arguably more sensitive to the higher ordered harmonics than **anything** else, it follows that for electronics to sound natural that is the kind of distortion that should be minimized (BTW it is this type of distortion that characterizes most solid state designs). When this is done, you can run much higher power levels and yet the system will not sound loud as all those loudness cues aren't being generated by the stereo.


The result is to naturally turn the volume up to get a realistic sound pressure. IMO, this is at the heart of the shortcomings of SETs, since they don't make much power and these harmonics are audible at any power level over about 20% of full power (which is why so many SETs are described as 'far more dynamic than their low power would suggest- its simply distortion that the ear interprets as loudness, showing up on transients that have the most power). The result is that even at relatively low sound pressure levels they sound loud. IMO/IME it is the mark of a good system that it always sound relaxed and never sounds loud until it really is (+95dB). The only way to get around this limitation with SETs is to use really high efficiency loudspeakers, which from what I've seen over the years doesn't happen that often- so many people are not experiencing the best that SETs have to offer. 

Thanks Ralph, having your MA-1's OTL's I agree that listening to higher levels without distortion it is an exceptional experience, I figured you were talking about your OTL's

Hi @atmasphere ,

Yes it is true. There are a few SET friendly speakers on the market.

But the hard to drive tower speakers like Wilson and Dynaudio will always sound compressed, and too loud at 95dB+ volume even with 1K watt amplifier.

I think a  low sensitive speakers fashion is a huge delusion of Hi-End market .

Regards,
Alex.