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Old 12th October 2007, 05:38 PM   #1
bwaslo is offline bwaslo  United States
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Default Audio DiffMaker freeware for checking for equipment effects

This might be relevant to the "cable debate" thread that is also going on here.

Audio DiffMaker has been revised to version 1.26, and the included Help file has been rewritten and additional examples have been added. As before, Audio DiffMaker is freeware, so feel free to download it and work with it yourself. You can also use Audio DiffMaker to listen to "difference recording" made by others, such as the ones posted at the Liberty Instruments' web site.

Download from:
http://libinst.com/Audio%20DiffMaker...ker%20Download

Available difference recordings ("Dyf" files) on the site are

- the effect of changing the IC type in an outboard DAC
- the effect of painting the edge of a CD with a green Sharpie pen!
- The difference between sound from using a ceramic disk capacitor and a film capacitor
- more to come, particularly if some of you send in dyf files you've made!

Audio DiffMaker is a program for demonstrating the possible effectiveness of changes (tweaks, etc.) on audio signals going through components. It works by recording the signal from audio gear before and after a change is made. The two recordings are aligned and subtracted to leave any difference (other than starting time or volume level) that may exist, and you can then listen to JUST the difference that was made. Useful for checking whether tweaks have any real effects on audio signals or whether circuit modifications are changing anything.

Audio DiffMaker is for Windows2000 or WinXP (sorry Mac and Linux users) . It is also usable with Vista, though a bit more complicated.

Also, watch for an upcoming article on Audio DiffMaker in AudioXpress magazine.
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Old 14th October 2007, 05:34 PM   #2
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that is a good program. you can do the same with sound forge, but this makes it much easier. (and of course, it is free!)

might also be used for mangling sounds for sound effects. for instance take the difference between a man and a woman saying the same thing.
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Old 14th October 2007, 07:36 PM   #3
bwaslo is offline bwaslo  United States
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But I don't think Sound Forge can do time alignment of two tracks to within less than one whole sample, though. Being aligned within just one sample is nowhere near close enough. Even if SF can shift in thousandths of a sample, it would take a long time to get them together manually using trial and error. DiffMaker uses trial and error, too (a "binary search" version of it), but the computer does the trials and evaluations in more steps than a human will be patient enough to do.

I've recently found that it is also important that sample rates be extremely constant between recorders and players (if they drift at different rates, a deep null won't be possible because the alignment will be out even just a few seconds away). If anyone is having trouble getting equal signals to cancel, try doing them with the recording soundcard's clock locked to the player's clock (or use the same soundcard to do the recording and the playing).

Thanks for looking at it.
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Old 14th October 2007, 10:04 PM   #4
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oh i see what you mean about the samples. you would not be able to do that in soundforge any accurate way at all.
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Old 15th October 2007, 01:41 PM   #5
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Haven't tried it yet, but man, what a great idea!
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Old 9th June 2009, 06:44 PM   #6
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Default Re: Audio DiffMaker freeware for checking for equipment effects

Quote:
Originally posted by bwaslo
Audio DiffMaker is a program for demonstrating the possible effectiveness of changes (tweaks, etc.) on audio signals going through components.
Hi Bill,

I've been playing around with Audio DiffMaker version 3.22 a bit, to evaluate the difference between high-res 24/96 files and their downsampled 16/44.1 counterparts. In testing the software, I first did the following:

1) Choose a reference file called, say, "file1.wav".
2) Make an identical copy of "file1.wav" called "copy of file1.wav".
3) In DiffMaker, for the "reference track", press the "Load" button and choose "file1.wav".
4) For the "compared track", press the "Load" button and choose "copy of file1.wav".
5) For the "difference track", press the "Extract" button.

DiffMaker then goes through its extraction process, and in its text file showing the status, it says:

"parameters: 0sec, 0.000dB (L), 0.000dB (R)..Corr Depth: 300.0 dB (L), 300.0 dB (R)"

So it looks like it's getting a perfect null here (within the 300 dB range of 64-bit floating-point maybe?). This all looks fine. However, when I play back the difference file, for a fraction of a second at the beginning, there is a sound that seems just like the reference file leaking through, but in the left channel only. Is this normal? If not, how do I eliminate this effect?
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Old 9th June 2009, 10:23 PM   #7
andy_c is offline andy_c  United States
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Default Re: Re: Audio DiffMaker freeware for checking for equipment effects

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Originally posted by andy_c
...but in the left channel only.
Scratch that. The particular file I looked at had silence in the right channel for the first fraction of a second. I tried other files and got a blip in both channels of the diff file at the beginning. After that, there was complete silence in the diff file as expected.
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Old 9th June 2009, 10:42 PM   #8
bwaslo is offline bwaslo  United States
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It can give you a burst of audio if the files are much misaligned to start with. It can only cancel where both files have audio that overlaps, so if one starts first, that part will get through till the other file's audio arrives to be subtracted from it.

If I remember right (it's been a long time!), I did something to block out that kind of thing if one runs longer than the other, to try to avoid blowing out someone's speaker or eardrum if they gun the volume trying to hear the residual. But not at the beginning I think.

I don't know what's the deal with th one channel only, though, so it could be something else. And now that I read your post closer, the files should be absolutely identical, so, I guess I don't know.

It might be some left-over from trimming that is done in the program on the compared file during processing?
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Old 9th June 2009, 10:47 PM   #9
bwaslo is offline bwaslo  United States
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Ok, looks like our posts crossed. Glad it's making sense.

The 300dB is just where the dB calculation bottoms out. You can't take 20log of zero without triggering a processor exception, so if the program sees zero (which identical files should give you), it just tosses back 300dB. It has to return something. You'll never get zero with real recordings (through A/D) because there will always be at least noise added.
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Old 9th June 2009, 11:07 PM   #10
andy_c is offline andy_c  United States
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Quote:
Originally posted by bwaslo
It might be some left-over from trimming that is done in the program on the compared file during processing?
The thing that's confusing me is that it's doing this when I have two identical WAV files I'm diffing. IOW, I take "file 1.wav" and in Windows Explorer, do a Ctrl-C, Ctrl-V on it to get "copy of file 1.wav", then run the two files through Audio DiffMaker. The diff file has an audible "blip" in the first fraction of a second. I was thinking it might have been something put there so the user can set the volume?
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