5% THD to .000 THD SOUND

That makes the point as well.

Bwaslo 8-1-2016 1:36 am edt
The percent distortion spec, as usually given, should be read for the POWER level that produces it (i.e., to indicate what the manufacturer assumes is the maximum power the amp might do).

This is an excellent point, among other excellent points in Bwaslo's post.  In looking further at the descriptions of various Kondo amplifiers I see that **all** of the SET and parallel SET models listed at their site (Kagura, Ongaku, Souga), and also the Gakuon II which is not listed as a current model, are indicated as having 5% THD at their specified maximum power ratings.  Presumably if their max power ratings had been specified less aggressively (i.e., somewhat lower), the specified THD would have been significantly lower.

Interestingly, though, their Overture integrated amp, which is a push-pull EL34 design, has its max power spec based on 1% THD.  Just guessing, but perhaps their thinking is that differences in how THD is distributed among the various harmonics when the two kinds of designs (DHT SET vs. push-pull pentode) are operated near their limits would result in say 2% THD in the push-pull EL34 design being subjectively more objectionable than 5% in the DHT SET designs.

On the other hand, though, as Atmasphere has pointed out on numerous occasions, for best sonics a SET should not be called upon to provide more than a small fraction of its rated power, as in contrast to push-pull designs the distortion produced by a SET becomes vanishingly small at low power levels.

All things considered, for an application requiring just a small fraction of the Kagura's rated power I'll retract my previous statement about ruling it out from consideration on the basis of the 5% number.  Although I would feel more comfortable in doing so if comprehensive measurements (such as John Atkinson provides in Stereophile) were available.

Best regards,
-- Al

Great insight into the realm of audio equipment and sound. Thanks. 

Al,
I'm not surprised that you recognized the significant and excellent points contributed by bwalso. I must say that I agree with your further comments.  These SET amplifiers if used in their sweet spot of operation have exceptionally low distortion.  I heard the Kagura driving efficient speakers at moderate or typical volume levels (definitely not lowered volumes). Most likely well within the amplifier's very  low distortion range.  This would to a large extent explain the wonderfully clear and natural presentation I described. bwaslo got it right with his post. 
Charles, 

Interestingly, though, their Overture integrated amp, which is a push-pull EL34 design, has its max power spec based on 1% THD. Just guessing, but perhaps their thinking is that differences in how THD is distributed among the various harmonics when the two kinds of designs

Well, marketing does get into it, too.  A SET amp, particularly one with no or low global feedback, won't have too much better distortion just below the power used to spec the 5%, while distortion of another amp likely will quickly get lower at lower powers.  So, quoting at a lower power won't markedly reduce the distortion figure for the SET, but can reduce it a LOT for feedback class AB amps, and of course that looks better to a customer having only a data sheet to look at.

At the 20dB or so power leve below clipping either amp is used on average at, though, the distortion produced is likely to be low enough to not matter in either case (Geddes did some research showing that for lower order distortions - which pretty much all amps do before clipping - people are just not very able to hear it; other factors are much more audible).

At very low levels, though, a badly biased class AB amp (or one for which the bias doesn't track thermal well) can have quite a bit of distortion relative to the output level due to crossover effects.  And crossover distortion (not speaker crossover -- class AB switchover distortion) is very high order and can be heard.  Class A amplifiers won't do that at low level,  (And, by the way, neither will class D amps.... its a class AB thing).