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RE: Don't you know

what you don't know is that most gear that is labeled "analytical" or "neutral" or "accurate" is really nothing of the sort. The "neutral" label on an amp is often given to one that doesn't properly express tonal color correctly...everything is a shade of gray. The "analytical" or "accurate" amp is often one that has over emphasized leading edges and high frequencies that results in a skelatal outline of instruments and spaces but lacking the flesh on the bones.

All of these are a form of DISTORTION and it is an insidious one because it steers towards what many consider good hifi "values". It is however distortion and it degrades the sound because it of how it steers the sound away from a natural sound and more towards and artificial or synthetic sound. It is no surprise given that the distortions that cause such colorations are the result of unnatural processes such as negative feedback in electronic circuits...something our brains were not evolved to handle the consequences it imposes on the sound.

CHeever and others have shown that even very low levels of higher order harmonics are audible and thus detrimental to sound quality. These high order harmonics are quite dissonant also have consequences on the perception of loudness...this can destroy proper soundstaging from sonic cues in the recordings.

Now, tube amps suffer from other distortions, mostly transformer saturation distortions. Those seem to affect more bass frequencies, since those are the ones usually saturating the core of the transformer, and have repercussions up through the midrange. This is what is mostly responsible for the classic "tubey" sound. If the tube amp is also using a lot of negative feedback then it can sound both tubey and slow AND glassy and hard (or analytical). THere are many bad sounding tube amps with both of these characteristics

If you look at the really good tube amps, they do not suffer significant distortion from their output transformers, they often use no feedback and as a result sound extremely open and transparent with no "edge" to the sound...very natural. Bass is also well controlled, despite the relatively low damping factors, but with natural tone color. The secret to the great sound of these amps (if not pushed too hard as they are often lowish power) is the Class A operation, which eliminates one of the more insidious and nasty distortions called zero crossing distortion, no feedack so that the distortion pattern is monotonic...i.e. exponentially decreasing with increasing order, excellent transformers so that distortion even at full power is less than 1% etc.

This results in an amp with LESS distortion of the audible kind than most so-called "analytical" or "accurate" amplifiers because our ear/brain is not an oscilloscope. Up to a few percent of 2nd order is inaudible but 0.01% of 9th order is likely audible.

You CAN do similar things with transistors and even eliminate the output transformer from the list of potential issues but it seems to be somehow more difficult or at least less popular to do. Nelson Pass has tackled it with his First Watt series (but all are low power like a tube amp). However you are then really getting the sonic signature of the device itself and triodes, pentodes, Mosfets and bipolar transistors do not sound the same and have distortion harmonic patterns based on their transfer functions (none of which are linear).

Hybrids without feedback can give a melange that is better in many ways to pure tube or transistor and in fact some of the very best I have heard were hybrids (KR Audio, NAT, Blue Circle) AND single ended.

Push pull creates a distortion pattern that is not really consonant with the way we hear, which is effectively single ended in nature.

The best SETs are more consonant with how the human hears so I would say that this is probably closer to the "truth" than a Class AB, push pull, high negative feedback amp could ever dream to be.

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