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Re: Even if the software were perfect ....

RE #1, nothing that you can do will take the sampling uncertainty out of the equation. It will still exist, and providing a square wave or impulse will not fix the problem or allow the software to align the signals any better (here, I am assuming that Mr. Waslo did a good job on the auto-alignment portion of his differencing software, which is not too terribly hard to do I am told). Nothing can be done either about the inherent and intrisnic amount of jitter the soundcard and computer system have, a reference sq wave or an impulse would not provide any better performance here.

I tried to do this once for audio cables, create a method of differencing the signal from two different cables, usng a "studio grade" soundcard with excellent specs. Thus, I speak from direct personal experience on this exact subject.

Unfortunately, the sampling uncertainty was a major problem, and the really frustrating thing was, that even when I used the soundcard itself to generate the test signal, running out of one channel into the other, you would think that the timing would be exact, the same every time. Nope. Modern operating systems apparently can interfere with the exact timing of the signals out and into a soundcard, ANY system activity will interfere with the actual timing of the ouput and input, and the system is never really idle. Forget about making two channel recordings of two different analog events, there is no way to eliminate the sampling interval errors.

RE #2, if you have those tests, measurements and criteria availble, then I can guarantee a Noble prize for you, for you will have now succeeded where countless others have failed.

To this day, WE DO NOT HAVE A COMPREHENSIVE SET OF MEASUREMENTS THAT WILL ALLOW US TO FULLY DETERMINE WHAT THE LEVEL OF SONIC ACCURACY TO THE HUMAN EAR WILL BE PERCEIVED AS.

It is NOT sufficient to say "this soundcard has XX bits of resolution, it has FR from DC to light +/- YY dB, it has distortion under ZZ % THD", none of these measurements, nor any combination of the traditional and typical measurements, can even begin to come close to fully defining what will be heard or not heard.

Thus, this statement:
"Jitter, linearity, SNR, samplerate/conversion rate, etc can all be had in quantities that will be good enough to make each associated error boyond the limits of even the most high performance human hearing in existence."
is just not true.

If you truly believe that the specs are fully sufficient to sonically characterize a audio component, then you won't even be bothering to perform such a test in the first place, and will likely also be willing to accept the results from any such "sonically perfect" soundcard differncing test, even though I have pointed out the fallacies involved with that type of testing.

See my reply to Dick Hertz down below, and I pose the same question to you that I posed to him at the end: why not create the ultimate systam based on one of these sonically perfect $200 soundcards?


Jon Risch

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