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I followed until this last bit, though would like to hear how negative feedback correlates to worse sonic performance... THD is a measure of linearity, and of course SINAD includes noise, so I am not sure exactly what you are requesting we (that is, @amirm ) to use instead of THD and SINAD? The 32-tone test is also a measure of linearity, and I did not think jitter below a reasonable level correlated well as a distinguishing metric either? Confused - Don
Like many design issues in audio, "it depends."
We've tested .0001% IC opamps that sound wrong and colored, and .0001% IC opamps that sound really good (we use them). We've done this kind of blinded AB testing for 30 years. I'm not saying we're the end-all, be-all in this conversation, but I will stand by our research and say confidently that distortion numbers very often have no correlation to the AB perceptual audio performance of an amplifier.
Is massive internal IC amplifier feedback the culprit? Maybe. In some cases. I frankly can't make the unequivocal statement. I remember a conversation with an audio IC designer from Burr Brown who shared his experience with massive internal feedback vis a vis THD and he said pretty much the same thing, and that's always stuck with me.
Yes, rather than using SINAD as a qualitative indication of audio engineering, I suggest presenting SINAD/THD/IM as quantitative measurements ONLY. No editorial as to "better" or "worse" or color ranking, or "better engineered," etc.. Split it out. Would rather see a pure signal-to-noise number without pilot tone, represented broadband and unweighted, naked and exposed without THD baggage along for the ride. Such is an example of a scientifically-accurate, qualitative representation, as are jitter, freq resp, linearity, filter responses, and many others.
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