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In Reply to: This's a slander posted by Feanor on April 16, 2024 at 04:38:23:
Measurements alone are not enough to tell the likelihood of a good sounding amp from one that sounds...well less good.
The proper WEIGHTING of the distortion products has to be done to extract truly useful information from an FFT. The SPL produced by the system with a given distortion pattern is also highly relevant because the SPL affects how sensitive your hearing will be to higher order harmonics.
Take a paper from Geddes, Cheever or even the simple equation from D.E.L Shorter and perform a transform on the distortion data and see what you get...then you can begin to understand something about psychoacoustic preference.
BTW. I did this once using the relatively simple transform from Shorter and using the distortion measurements from Soundstage magazine. Sadly, I have lost this file when a hard drive crashed.
The amps that had the best adjusted distortion figures were a Lamm and a Wyetech SET.
Cheever's transform is far more complex and uses SPL as part of the equation. This is relevant because SPL affects your hearing sensitivity and what becomes more audible. He comes up with a number and the lower that number the better sounding or "pure" sounding the amp should be. Essentially the closer you get to 1, the better the amp mimics your hearing's own distortion and so the distortion "hides" in the masking that is a known auditory phenomenon.
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Follow Ups
- RE: This's a slander - morricab 04:39:17 04/17/24 (9)
- what I take from Geddes/Cheevers ... - Feanor 13:28:39 04/18/24 (8)
- RE: what I take from Geddes/Cheevers ... - morricab 01:44:54 04/19/24 (7)
- Irrelevant in case or lower than -130 dB - Feanor 04:14:40 04/19/24 (6)
- RE: Irrelevant in case or lower than -130 dB - morricab 07:40:14 04/19/24 (5)
- Why? I'm tempted to say "imagination" - Feanor 04:31:57 04/24/24 (1)
- RE: Why? I'm tempted to say "imagination" - morricab 10:02:12 04/24/24 (0)
- he would never be allowed to sit on a panel - Story 12:33:52 04/19/24 (0)
- "Why then..." I am sorry, but no one knows the answer - Victor Khomenko 11:43:12 04/19/24 (1)
- RE: "Why then..." I am sorry, but no one knows the answer - morricab 08:57:15 04/23/24 (0)
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