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Old 16th November 2012, 08:35 PM   #29371
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Quote:
Originally Posted by PMA View Post
Well, I think speaker distortion masks any distortion of well designed amplifier. Anywhere, even for "high order" components. Recently I made a large set of FFT measurements at acoustical side, i.e. with microphone at listening place. Change of two amplifiers that measure different electrically, but below 0.01%, made absolutely no difference in FFT spectrum of harmonic distortion and ccif imd. To me, nonlinear distortion is not an answer of different sound of well designed amplifiers.
If that were the case there would be no use for (or developement)
of amplifiers that have less distortion than speakers.
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Old 16th November 2012, 08:36 PM   #29372
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More randomizing for listening tests? :-)

The rhythm or cycling seems to be so that the brain isnt blocking other input or something new/important.

Last edited by RNMarsh; 16th November 2012 at 08:40 PM. Reason: tweaking SY
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Old 16th November 2012, 08:41 PM   #29373
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jcx, 64K samples of 48kS/s takes 1.36 second. Even if averaging is set to 1, the FFT averages information during these 1.36 seconds. Non-periodic phenomena are suppressed in resulting amplitude. If you go faster (shorter FFT length), like 8K ... 1K, whatever, you get the view of shorter event, but loosing resolution (bin width). So, we may go fast with poor resolution, or slow with high resolution, but averaged result valid only for periodic signal components.

I know that FFT is a frequency domain interpretation of time domain signals (but we need not only amplitude spectrum but phase spectrum as well to get all the information), but for transients FFT is quite useless for the reason of poor resolution. Time domain is much better then. I agree, give me a 20-bit system at more than 10MS/s and then we can analyze transient signals properly. But not with 100kS/s.
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Last edited by PMA; 16th November 2012 at 08:44 PM.
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Old 16th November 2012, 08:42 PM   #29374
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> we haven't diverged into a sub-thread planning the great listening test in a while

The great test (in this case) is to run music through 10 followers and notice the differance (aurally) an eleventh makes.
(or if you believe there are 10 at the studio, one makes)
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Old 16th November 2012, 08:42 PM   #29375
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Originally Posted by hitsware View Post
If that were the case there would be no use for (or developement)
of amplifiers that have less distortion than speakers.
No, you only need to concentrate to other effects than a mere non-linear distortion.
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Old 16th November 2012, 08:48 PM   #29376
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If that were the case there would be no use for (or developement)
of amplifiers that have less distortion than speakers.
If you look at the build quality of some amplifiers you will see a lot spent on RFI shielding, proper routing of wires, high quality power supplies, etc. and often a fairly simple circuit topology. The quest for lower THD goes nowhere, there aleady are things like Halcro.
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Old 16th November 2012, 08:52 PM   #29377
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Someone has mentioned a short impulse. Well, the problem of short impulse analysis (Fourier) is that one would need very high impulse to get enough energy and enough resolution. We may get basic amplitude and phase responses from impulse response and that's all. No new insight and not enough resolution, not enough dynamic range.
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Old 16th November 2012, 09:00 PM   #29378
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If you look at the build quality of some amplifiers you will see a lot spent on RFI shielding, proper routing of wires, high quality power supplies, etc. and often a fairly simple circuit topology. The quest for lower THD goes nowhere, there aleady are things like Halcro.
Hello Scott

So are you saying that the way forward is to concentrate your efforts on reducing RFI and amount of ripple on the power supplies.
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Old 16th November 2012, 09:01 PM   #29379
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Scott; you do not have answered my question about that.
I would think seconds depend on top/bottom of the wave effects so for each device the phase is a coin toss. I was not really addressing identical stages at identicle operating points connected in series.

There are lots of circuits with harmonic null properties.
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Old 16th November 2012, 09:02 PM   #29380
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Hello Scott

So are you saying that the way forward is to concentrate your efforts on reducing RFI and amount of ripple on the power supplies.
Probably more fruitful that chasing the last .001% of THD.
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