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Old 21st January 2012, 02:42 AM   #1201
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No, believe I can't hear -80 dB 2'nd harmonic of my Pyramid amps on a half of output power (40W), especially when it goes all way down under noise floor when power goes down.

Your optical couplers are fantastic, but THD and dynamic range are quite different things.
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Old 21st January 2012, 02:46 AM   #1202
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Originally Posted by SY View Post
Really? I would have thought 80dB. Could you explain to a dummy how you got that number?
I assumed Power ( audible) vs voltage(signal)??
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bet you can't hear 80 dB down SFDR
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Old 21st January 2012, 02:52 AM   #1203
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THD measurement operates by voltages.
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Old 21st January 2012, 02:55 AM   #1204
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Originally Posted by vanderpol4 View Post
I assumed Power ( audible) vs voltage(signal)??
That's the difference. Never occurred to me to use power. Thanks!
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Old 21st January 2012, 03:11 AM   #1205
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Really? I would have thought 80dB. Could you explain to a dummy how you got that number?
Guys that live in the "other" world, Wireless and RF, tend to think in terms of power, not voltage. They always use 10 log ratio, not 20. But for audio voltage measurements, it should be 20 of course.
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Old 21st January 2012, 03:34 AM   #1206
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Default Life size model of the human cochlea with optical readout

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Originally Posted by Wavebourn View Post
No, believe I can't hear -80 dB 2'nd harmonic of my Pyramid amps on a half of output power (40W), especially when it goes all way down under noise floor when power goes down.

Your optical couplers are fantastic, but THD and dynamic range are quite different things.
Yes and which one matters????? which one can we actually discern?

Gan Zhou and I with Dana Anderson once wrote a paper "life size model of the human cochlea with optical readout" published in JASA. The physics of the cochlea were amazing; as you probably know up to 500 hz a WKB 1-D approximation modeled cochlear traveling wave response pretty well; the basilar membrane response is really quite broad. Above 500hza 3-D model is required and the traveling wave ( like a Tsunami ) membrane deflection is much more peaked in response. past ~ 3khz the the cochlear pressure response is very peaked and we found 15khz was about 5mm from the stapes, hence the 25khz or so discrimination threshold for lucky individuals.

Sadly we never ran two tone etc. through the lab cochlea but the 1khz and below basilar membrane response seems really broad for a highly discriminating response to say an in phase 500hz and 1khz two tone signal.
above 3-5khz and it would be pretty localized, so I would guess 2nd harmonic 1khz and below would be threshold limited on auditory response
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Old 21st January 2012, 04:36 AM   #1207
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I agree with you that 100 times difference in voltage levels mean 10 times difference in sound pressure. And my own understanding of audibility of errors goes from other direction than analysis of physical hearing apparatus: perception is more than physics, it is combination of sensory perception and mental image manipulations. And if it grew up during evolution to recognize sounds distorted by physical media, such distortions are perceived as information about sound sources and environment, while distortions added by electronics differs a lot, especially in dynamics.
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Old 21st January 2012, 05:04 AM   #1208
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I agree with you that 100 times difference in voltage levels mean 10 times difference in sound pressure. And my own understanding of audibility of errors goes from other direction than analysis of physical hearing apparatus: perception is more than physics, it is combination of sensory perception and mental image manipulations. And if it grew up during evolution to recognize sounds distorted by physical media, such distortions are perceived as information about sound sources and environment, while distortions added by electronics differs a lot, especially in dynamics.
Totally agree. For example a simple experiment, listen to your favorite music drummer, sax etc. and "close " one ear, I know for me the timbre, "air" , "realism" vastly changes for the worse; ( haven't tried it with headphones though), I have always suspected the "difference" in the sound of amplifiers at moderate volumes has something to do with our sensitivity to lateral phase & amplifier interchannel crosstalk with phase delay; hence the love of dual mono power supplies..
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Old 21st January 2012, 05:20 AM   #1209
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Or, go to Siberia during summer, seat on some nice meadow with flowers, look on the water in a lake... After half an hour try to explain how do you locate mosquitoes flying around your head and body, killing them without paying attention.
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Old 21st January 2012, 09:00 AM   #1210
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I agree with you that 100 times difference in voltage levels mean 10 times difference in sound pressure.
That leads to confusion too, SPL is dealt with like voltage (mV/PA for instance). If you want real confusion photodiodes are A/W.
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