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In Reply to: What if accuracy is boring? posted by 13th Duke of Wymbourne on November 26, 2024 at 14:07:54:
Given that I have found rather consistently that the most boring amps I have heard are the ones that use copious amounts of negative feedback to get the numbers down to where they are.
Cheever noted that those great measuring amps are not linear at all when the feedback loop is removed. He looked at the Hafler DH500, which has very good measurements even today, and he found that when he removed the feedback loop the amp produced 25% THD at a modest power. The distortion FFT was a wide spectrum of high order harmonics that will sound rather nasty.
Compare that to a no feedback Class A triode amp where you will find at modest power typically <1% THD and nearly all of that is 2nd-5th order harmonics.
His hypothesis was that the more linear an amp is open loop (i.e. no feedback) the better it will sound and that feedback obscures the picture because, it does improve the horrible measurements that nearly all SS amps would have if not for feedback but seems to also take away something from the sound...not jsut distortion. Feedback suppresses low order harmonics more than higher order harmonics and even generates additional harmonics (see Baxandal paper and Crowhurst).
If you had two amps where one essentially made all music uninteresting to listen to regardless of the source, speakers, cables etc. and another amp that gave a wide range of results depending on the recordings played. Some sound dull, some sound exciting and alive and most sound somewhere inbetween. Let's further say that the dull sounding one measures significantly better even though in listening it kind of made everything sound dull. Would you say then that the better measuring but subjectively dull amp is more "accurate" or would you take the worse measuring amp that shows more variety from recording to recording as the more accurate? I would choose and consistently choose the latter.
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Follow Ups
- RE: What if accuracy is boring? - morricab 05:12:04 12/02/24 (1)
- The question is rhetorical and simple, a long non-answer is unnecessary - 13th Duke of Wymbourne 16:31:02 12/05/24 (0)
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