Con artist's beware! Audio DiffMaker is on the job.

[TLS Guy]

I just finished a post about tubes in a CD player, and got into discussion of the superstitions of the high end.

Yesterday I received my January 2008 copy of audioXpress.

On page 16 Bill Waslo, who is an analog/RF engineer, and develops audio test equipment and software for Liberty instruments, has an important paper.

The paper is titled "Of Tweaks, Mods and Evidence." This is an important paper. He has developed software that applies digital subtraction techniques to audio. I'm very familiar with digital subtraction. Radiologists use it, especially in neuro radiology to identify lesions such as aneurisms that might be missed otherwise. Films taken before and after X-ray contrast are digitally subtracted. This leaves a clear picture of only the blood vessels.

Bill Waslo has applied this to audio. It works like this. Say you want to see if an exotic cable has a benefit. You make a recording with cable x and then cable y. The program level matches does digital subtraction and makes a wav. file of the difference signal. What is in the wav. is the difference. Nothing in the wav. no difference. You can use this to check for exotic spikes, caps anything you want, except electromechanical devices were there are too many random variables under the conditions of the test.

This technique is extremely sensitive. The software is free! It can be downloaded here.

http://www.libinst.com/Audio DiffMaker.htm

I'm going to order my ear plugs to stop going deaf from the howls of the high end. We likely will get more than a few belly laughs along the way.

This is important. It gives us a valid logical tool to confront a lot of loony superstition, that distracts from, and delays solution to real problems. If there is merit in a tweak or mod, it will clearly show.

 

[3db]

TLS

having studied electrical engineerring at university, especially the analog stuff, I was always amazed at how powerful the placebo affect is. People buying high end cables believe they actually hear a difference when there is no difference.

This digital subtraction that you speak off, is it similar to autocorrelation prinicples? The prinicple behind auto correlation is hat anything that is spectrally the same gets filtered out with only the changes appearing. They use it to find signals burried deep in nosie. Its been over 20 years since I;ve seen this stuff so I may be a lot rusty on this.

 

[fmw]

I know this was done a few years back simply by comparing two digital recordings bit for bit. I think this is the same approach. It's a noble effort but not terribly important. Those of us who know better, don't need it to tell us the tweaks and cables are nonsense because we've been through the blind listening tests. Those who believe in it won't be deterred by another test. They never have been.

I saw post here the other day that linked to an audiophile explaining the advantages of recording to a black CD. In his own "white paper" he explained that the files on a black CD were identical, bit for bit, to the same ones on a regular CD. However, he heard an amazing sonic improvement by the bits that had been recorded on the black CD. This guy looks at the proof that the sound is identical and still doesn't believe it. He believes what the mind's placebo affect tells him instead. I've seen this sort of thing many times. The audiophiles will always say "I know what I hear." But, of course, they don't. None of us do.

 

[TLS Guy]

I know this was done a few years back simply by comparing two digital recordings bit for bit. I think this is the same approach. It's a noble effort but not terribly important. Those of us who know better, don't need it to tell us the tweaks and cables are nonsense because we've been through the blind listening tests. Those who believe in it won't be deterred by another test. They never have been.

I saw post here the other day that linked to an audiophile explaining the advantages of recording to a black CD. In his own "white paper" he explained that the files on a black CD were identical, bit for bit, to the same ones on a regular CD. However, he heard an amazing sonic improvement by the bits that had been recorded on the black CD. This guy looks at the proof that the sound is identical and still doesn't believe it. He believes what the mind's placebo affect tells him instead. I've seen this sort of thing many times. The audiophiles will always say "I know what I hear." But, of course, they don't. None of us do.

Digital subtraction is much more powerful. If there is nothing left after subtraction, the signals are the same. There is no rational arguing against it. Digital subtraction is an elegant powerful tool.

 

[fmw]

Digital subtraction is much more powerful. If there is nothing left after subtraction, the signals are the same. There is no rational arguing against it. Digital subtraction is an elegant powerful tool.

I don't recall audiophiles ever making rational arguments, do you?

 

[TLS Guy]

I don't recall audiophiles ever making rational arguments, do you?

No, and that's a serious problem that turns attention away from real problems. There are still lots of those

 

[AcuDefTechGuy]

Oh, come on, guys. Where's the fun in that if you totally discredit and disprove all those "golden ears"?

 

[fmw]

You're right. They are a pretty easy target.

 

[krabapple]

I already know what the subjectivist audiophile reply to subtraction/bit identity arguments regarding digital sources is going to be because I've *seen it* on audiophile forums before (e.g. Steve Hoffman's loony bin). It goes like this:

Skeptic: see, these two CDs are bit-identical. They shouldn't sound different.

Audiophile: But reading the data in a file, and outputting it as audio, is not the same thing. Who knows, maybe somewhere between read and output, difference is introduced. Either way, I hear it and therefore it must be real.

see for example this post by mastering engineer Barry Diament:
http://www.stevehoffman.tv/forums/showpost.php?p=3003221&postcount=69

Now, to a small extent, the audiophiles have a point -- I can think of a few cases where two different players might not play the same disc identically,. e.g., if the disc contains a lot of intersample peaks over 0 dbFS, one player might reconstruct them better than another. Also, there is limited 'white paper ' evidence, from the late Julian Dunn and colleagues, that a given CD player can inject noise into output depending on properties of otherwise bit-identical discs (these properties were never identified, AFAIK). The white paper is here:
http://www.prismsound.com/m_r_downloads/cdinvest.pdf

HOWEVER: there is no evidence that any of this is routinely audible. Dunn did blind listening tests of bit-identical discs, using audio professionals as subjects, and results were not better than random. And the audibility of clipped intersample peaks is dependent on their concentration and size; moreover, the intersample overs case I proposed, would not explain why the SAME player would play bit identical discs differently...which is what audiophools claim. None of this points to bit-identical discs sounding different as a matter of course.

I would hope the question could be laid to rest for audiophiles making such arguments if the *analog* output of bit identical discs, could be shown to completely cancel out. I've tried Diffmaker and it might be *too* sensitive for such purposes -- it would likely show differences that are real but tiny -- basically random small fluctuations in analog output stages -- and thus not likely to be audible. But it might make an interesting experiment anyway.

 

[krabapple]

Digital subtraction is much more powerful. If there is nothing left after subtraction, the signals are the same. There is no rational arguing against it. Digital subtraction is an elegant powerful tool.

And even if something is left, it might not be audible.

 

[AcuDefTechGuy]

You're right. They are a pretty easy target.

I just absolutely love it when they rave about their $1,000 wires and cables.
It just makes my day!
I don't want that to stop.

 

[mtrycrafts]

Digital subtraction is much more powerful. If there is nothing left after subtraction, the signals are the same. There is no rational arguing against it. Digital subtraction is an elegant powerful tool.

Yes, but if it does see a difference, then the question is, is it audible?
Certainly a measured difference doesn't make it audible.