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In Reply to: RE: Its not that I don't believe Harry posted by Tre' on October 27, 2020 at 09:01:54
You won't get any objection from me that this is largely a true statement (although the implementation matters).
I am interested in WHY that is the case.
Follow Ups:
If the 2nd and 3rd are in sufficient quantity, they will mask the presence of the higher orders. In addition, it appears that they also add to the sense of detail and soundstage. IMO more research is needed as to why and how of that last bit.
The 3rd is treated by the ear/brain system in the same way as the 2nd- it contributes to 'warmth' and 'body', unlike any of the other odd orders.
This masking seems to be why a tube amp (and especially one with triodes running no feedback) is able to sound smoother than solid state, even though its higher ordered content is at a higher level than solid state amps often have.
I'm really using some short hand here with no discussion of phase margins, gain bandwidth product and the like and the significance of that to the use of feedback, but that's been covered pretty well elsewhere. I'm just mentioned it to point out that the use of no feedback is part of the recipe.
2nd and 3rd order will not mask higher orders until the volume goes op (the masking effect is level dependent). At lower levels those higher orders will be exposed to our hearing.
I think the difference with tube amps (without feedback...with feedback it can sound as strident as SS amps can) is that at lower power outputs the high order harmonics are much lower than typical in an SS amp relative to the lower orders.
There seems to be more than masking at work as it seems the pattern itself seems to matter (hearing is much more than just the mechanism in your ear...there is anticipation of what to hear based on experience).
Jean Hiraga discussed this (he called it monotonic, I would call it exponential decay) and Cheever also highlighted this and goes into a lot more depth about the perception aspects and level dependence.
I was nutshelling it; we're on the same page here.
About the only way I can see around this is to have so much feedback that the amp can compensate for the distortion added by the feedback itself. But that takes a lot of feedback (over 35-40dB) which is really impractical in most tube amps. For that matter, its been impractical in most solid state amps too, which is why there is over a half century legacy of bright harsh solid state amps with few exceptions.
'This masking seems to be why a tube amp (and especially one with triodes running no feedback) is able to sound smoother'
this may sound [or be] stupid but I liken that to 'up-sampling' where what's missing is added by a synthesized continuation of the waveform
it has to be a more complex phenomena in the analog domain but that's how I visualize it, as an 'additive effect', and when listening your ear / brain does the rest of the task
regards,
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