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nonsense

It looks like this topic has been heating up since I was last here. Sorry I've been away and missed much of it, we had a critical office computer self-destruct and have had to scurry to get something up and running to replace it. Anyway..
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"To put it as simply as possible, unless the soundcard has enough resolving power and fidelity that you would be able to listen to music through it and use it for all playback chores, without being in the least dissatisfied with the playback quality of the soundcard, then this method would not be able to reliably detect any differences for a system that was at or above (less signal aberrations) the level of performance of the soundcard."

That is just plain nonsense. We do not need record and playback capability that reproduces things with perfect fidelity. We need only for it to respond *in some audible way* to the changes we are trying to detect. You neglect the fact that we are not trying to make something sound the same (as we wish in traditional listening tests in a stereo system) -- we are trying to see whether there is *anything audible* left in the processed difference.

It only matters that some audible trace of the difference is left in the record/play process. This is particularly true for this test --- but NOTICE THAT:

!! THIS IS ALSO TRUE FOR DETECTING CHANGES BY EAR. !!

Just look at where your reasoning leads ---

Does an audiophile need perfect recordings in a perfect room in an otherwise perfect system in order to tell differences between cables, tweaks, etc? If so, I'd have to conclude that he must not really hear any of these differences, because no system or room is even remotely perfect. Do we agree with that conclusion?

Is every recording (that he uses to evaluate gear with) superior to every piece in his audio system? Even recordings that were made before the invention of the device/cable/tweak that is making the difference (wouldn't that tweak have to have been used in the recording studio, wired with better cable than is being tested?) One of my favorite recordings for ambience is Belafonte at Carnegie Hall, has nothing improved since that was recorded about 40 years ago?

For that matter, can an audiophile hear differences in a component when it is not the weakest link in his listening system because some less revealing component is in the chain somewhere? Can he detect a change of cables using loudspeakers less transparent than than either cable? (If so, I WANT those loudspeakers!!).

"In order to make this clearer, I will provide an over-the-top-example:
lets say the soundcard used had an ACTUAL linearity such that it literally failed to respond to any data below the 15th bit, or put into a different framework, that pretty much everything below -90 dB full scale was obliterated."

Yes, that is over the top (one might even suggest, a "straw man"). But, ok, lets say we have that hypothetical soundcard. When recording, the signal being recorded is not below -90dB, it is dynamic varying with time over a wide range -- it contains large waveforms. Say there are differences between the cases being tested that, if isolated, are below -90 relative to fullscale, and are audible. So do these differences have *no effect* on the recordings made? Of course not. They will change values determined by the converter at many sample points. At some point, perhaps one sample value that had been on the edge of being +12,345 instead of +12,346 will get tipped over to +12,236 due to the tiny "difference" being made. An effect will show up in the subtraction result. And (back 'under the top), the actual dither or noise with real hardware actually allows signals to be resolvable below the least significant bit, just as sounds can be discerned below noise from analog sources.

'Under the top', still, in a real test with real gear, the difference track won't be 90dB reduced. In a very good null (made from a particularly quiet audio system), when turned up higher than usual, it will leave a soft, roughly white noise floor. But people get to listen to the result themselves, they don't need me (or you) to tell them what they can or can't hear or what they think may be significant.

And why the concerns about -90dB detections (reduced from the -120dB argument in an earlier post)? (That rules out use of vinyl, you know. An exceptional vinyl recording and setup can maybe get to 73dB S/N.) Are all possible differences between cables, etc., less than 90dB down? Because otherwise the example above could, at best, apply only to such circumstances.

****Should anyone who can solder want to really hear what 90dB below their listening level sounds like, you can make an attenuator to get that that with a series 330K resistor in the "hot" path from input to output, shunted to ground by a 10 ohm resistor on the output end. Just insert that attenuator into a line-level signal path and compare playing music with and without, at equivalent volume levels. No need to just read discussions about how low that is, hear it in actuality***

I have made a DiffMaker run using a decent (but not SOTA) soundcard. It was two recordings, made through two different cables, neither of premium status), and the resulting difference was of course not 90dB down, I'm sure. But when I listen to the difference at the same gain as used to listen to either one, nothing is heard in that case. Is the soundcard cutting the info out? To test, I took one of the recordings and dubbed my voice over it at a very low level, so that I couldn't hear it in the mix. When I subtracted the two recordings, I still heard nothing at appropriate gain. Until I turned the gain up, and then, there was my voice (but still no trace of the original recorded track). So, the differences must have been weaker than my overdubbed voice, at least to my ear in my room.

"If it is not, then it could be masking other components or systems aberrations and differences to whatever extent that the soundcard lacks ultimate sonic perfection."

Picked that sentence out because it illustrates a fundamental misconception. "Masking" is relevant to conventional listening tests. People may not be able to notice some things in the presence of other things. In DiffMaker tests, though, such masking "other things" are removed in the subtraction. Masking isn't a factor -- at all, unless possibly the noise is so high as to be noticeable. The test is between hearing something or hearing essentially nothing.

"...no sound card out there can pass this test, they all add something that is not 'musical' to the sound, when compared to the original 'source'..."

And there's another one. If I "add something" to A, and add the same something to B, then subtract A from B, that "something" vanishes, per the simplest algebra. Unless the added something can also make the difference we want to isolate VANISH (not change, mind you, but VANISH without a trace), the difference will be left.

"If you record one set of components, and then make a change, and record another set of components, the actual timing of the sampling will not be synchronized."

Everyone, please read the writeup about the test we are talking about before offering such objections. The synchronization is a main function that the software DOES, as is clearly described on the Audio DiffMaker page.
Besides, think it through: if the synchronization were incorrect, then the result wouldn't be silent, right? Synch (delay) errors, and gain errors leave a (false) difference. Silence only happens when all that stuff is right.

"Now, we would have the sample to sample timing error CHANGING, and the jitter differences between the ADC and the DAC would only add to the difference error, not cancel."

Ok, but all these things you object to will leave a difference error, not a silent null. And any lister listens to that error. If he hears nothing he considers significant, then that problem must not have been a factor, right?
If he hears something significant, then possibly the test has an error; or else a true difference has been found. It's easy to check for the error, by the way -- record the exact same situation twice, and subtract. If you hear something significant in that difference, then the setup or gear is inadequate for what you are testing.

"Note that the kinds of faults and problems I am mentioning almost all result in a false null, that is, little or no difference file content."

How so??? I see only ONE conceivable scenario in the post, which is that rather absurd case of the A/D converter that somehow knows what part of a signal is the -90dB part so it can ignore it in its conversions. EVERY OTHER problem you mention would result in a false DIFFERENCE. A NULL is very difficult to achieve, everything must go right for that to happen.
How could the other claimed faults result in a "false null"?
How would the faults mentioned above result in the two recordings being the same to within an inaudible degree, even if what they recorded WAS different to an audible degree?

"Of course, far too many objectivists will take such a result as "proof" that there are no sonic differences, but the actual truth would be, we just wouldn't know for sure."

I really try to not offend, but: have you tried making a DiffMaker test? The statement above sounds EXTREMELY defensive to me. You are in effect implying that you fully expect the test to result in no differences you can hear, and are getting explanations all ready to defend against that. Why?

Have you tried it already and found no difference in things? Because I haven't tested many of the controversial things, myself. I don't have access to premimum cables or tweaks, don't have extra $$ laying around to buy any. (I'd also would prefer to just provide the tools and let others test themselves and make up their own minds). So, how do you KNOW that the tests will show "no difference" to most listeners?

There is only one set of DiffMaker recordings (that I know of) which has been posted anywhere, and it, in effect, reveals a difference (to my ears, at least) between different types of coupling capacitors (though the scenario I used is pretty much stacked in favor of that result).

May I also remind other inmates that the results of the DiffMaker test are not purely objective (though they could be modified to be, but then someone would have to decide what each number meant...). The result of DiffMaker is a WAV file that anyone interested listens to -- no graphs, no numbers, no one can say what someone else hears in that file.

Another correction, contrary to reports elsewhere, DiffMaker is not a commercial product, it is freeware. And I claim it to be only a tool, not a religion!


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