Audio DiffMaker
signal difference extraction software
from Liberty Instruments

Audio DiffMaker is completely freeware, doesn't contain advertisements, and doesn't try to cajole you into "upgrading" to a non-free version.  There are no strings attached.

Version 2.0 now available here for download

See the full Article on Audi DiffMaker in AudioXpress magazine, Jan 2008

Last Revision: 15 December, 2007
-version 2.00-

Added compensation for sample rate drift in decks and soundcards.

Audio DiffMaker is a freeware tool set intended to help determine the audibility of things intended (or expected) to change sound quality in an audio playback system. It finds the absolute difference between two audio recordings. 

The difference recording  that results is only what has changed between the two recordings.  If anything - a change of component, a treatment, mechanical damping, etc. - is having any audible effect on the audio signal in a system, the difference recording will have audible content. The end result is primarily intended to be evaluated by ear.

This relatively simple idea can be used demonstratet whether some products can alter audio signals in audio equipment.  The DiffMaker concept is simple, but making it work was not simple.  Proper operation requires that the two signals be precisely aligned in time and in signal level.  Time alignment must be done to within a small fraction of a sample period.

Audio DiffMaker  is intended to highlight only whether a change is being made, but not whether any actual change is an improvement or a degradation -- that part is still left to the tastes of the listener.  

Changes detected by Audio DiffMaker are not necessarily audible changes for any given person.  Some changes will not sound different, and some are too weak to be heard when accompanied by the unchanged part of the program material.  But a silent difference track can only result if the two tracks being compared are unchanged (the same).

The DiffMaker process, by its very nature, avoids masking effects because it removes the large signal that masks subtle details.  Unlike traditional listening tests, differences can be detected even when buried by program material or if affected by imperfect components in the system.

What Can Audio DiffMaker Do?
Some of the tools within Audio DiffMaker can be used to:

• precisely align two similar audio tracks to the same gain levels and timing
• extract and listen to even very tiny differences between pairs of audio tracks
• quickly compare two or more recorded audio signals under precisely gain-matched and time-matched conditions.
• record sounds at various sample rates and bit resolutions up to 24bit/192kHz with the "Recorder" tool.
• select and copy sections of audio tracks, trim them, or "rip" them from audio CDs, with the "Trimmer/Ripper" tool.
• quickly see the responses of devices or entire audio systems (even rooms) using the included high resolution 1/6th octave frequency/spectrum "Response Analyzer" and matched pink noise source. 
• Compact multiple WAV files, and a text description, into one easily transported "DYF" file.  Just double-click on a DYF file in Explorer and Audio DiffMaker will open and load the files, ready for listening.

included 1/6th octave pink noise analyzer.
Also very useful, with microphone and easily made Pink Noise CDR, for setting up subwoofers in listening rooms!

Doesn't this process require ultra-high end recording equipment? 
Not really*, because DiffMaker doesn't try or need  to accurately reproduce music --  it is only trying to help detect whether anything has changed, which is a much less demanding requirement.  The sound card used doesn't need to be completely transparent or of highest pedigree.  It only needs to be capable of responding to any differences that may occur (even if those differences aren't reproduced perfectly) and of not burying any significant differences in added noise.

How can you tell whether the equipment was good enough in a DiffMaker result?  You can listen to the result, and note the level of any difference and/or decide if any remaining noise is high enough to be maybe covering something that may be important.  In other words, if the gear isn't good enough, you'll be able to hear it -- imperfections in gear can't make different sounds be the same, but they can add noise that is not silent (and noise is always different, even from other noise, and is revealed in the Difference result).

*though opinions do seem to vary on this!

The computer used should have 512MB memory minimum and run at 700MHz or higher. It should ideally have a CDROM drive and about 1GB minimum spare hard space, and run the Windows 2000, Windows XP, or later operating system.

Audio DiffMaker can use one or two sound cards and operates in stereo or monophonic mode. For generating your own difference files, one of the sound cards must have stereo line-level inputs. For listening only, only playback is needed.

Audio DiffMaker Install Package, including software, needed auxiliary files, and Help files (1.8MB). 
Click here to Download Audio DiffMaker

For some pre-made Dyf files to listen to with DiffMaker, see "Downloadable DiffMaker Dyf files", over to the right -->

• Changing interconnect cables (compensation for cable capacitance may be required)
• Different types of basic components (resistors, capacitors, inductors)
• Special power cords
• Changing loudspeaker cables (cable inductance may need to be matched or compensated)
• Treatments to audio CDs (pens, demagnetizers, lathes, dampers, coatings...)
• Vibration control devices
• EMI control devices
• Paints and lacquers used on cables, etc.
• Premium audio connectors
• Devices said to modify electrons or their travel, such as certain treated "clocks"
• Different kinds of operational amplifiers, transistors, or vacuum tubes
• Different kinds of CD players
• Changing between power amplifiers
• General audio "tweaks" said to affect audio signals (rather than to affect the listener directly)
• Anything else where the ability to change an audio signal is questioned

Will Audio DiffMaker always resolve these issues?
   No. Tests can be inconclusive because of noise or difficult system or recording conditions.  And because the final result (the "Difference" recording) will still be evaluated by ear, human judgment is involved in determining whether the changes are significant, unfortunately leaving much room for disagreement.  Technique and judgment is important also, as with any test.  It is important to account for known effects.  Differences that are uncovered, if due to expected causes (such as can be happen from changes of cable capacitance), won't be very useful and may be hiding other more interesting differences.

  There is still no way to prove something  is inaudible, and DiffMaker can't change that. 

   But the Audio DiffMaker process can make signal differences that do exist more obvious, which may lead to less disagreement. And in an Audio DiffMaker test, the final Difference result is recorded to a "wav" file that can be replayed by anyone, for themselves, at any later time using the freeware software. The result  file itself is available, for any interested person to evaluate.

Can Audio DiffMaker be used to test any component?  
No. Like any test tools, it must be used within its limitations.  Testing with acoustical signals (such as loudspeaker tests by microphone) is not generally practical because of the degree of repeatability that is required.  Testing using phonograph  sources will also not typically be repeatable enough for DiffMaker tests.

Best results will occur when the recording sound card is locked to the signal source (the same soundcard, or a CD player with a digital output).

Downloadable DiffMaker "Dyf" Files of some DiffMaker test results

These are downloadable DYF files containing some example  tracks (original and difference) you can listen to.  After installing Audio DiffMaker, download any of  these files using the "Save to" option (right-click on the link), then double-click on the saved file name to listen to it with DiffMaker.

NOTE:  Internet Explorer 7  for some reason wants to save the DYF files as HTML files (it will change the extension to ".htm" -- I have no idea why)!  During or after saving the file, you will have to change the extension back to ".dyf" to run it with DiffMaker.  Firefox doesn't have this problem.

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Series Cap Test:: This file shows the difference to an audio signal of playing  through a polypropylene capacitor and through a cheap ceramic disk capacitor, in a setup contrived to highlight their differences.  Documented in the DiffMaker Help file example.
Download: SeriesCapTest.dyf (2.7MB)

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Opamp Change Tests: These files reveal the difference between using an NJM4580 and an LM4562 as the gain/buffer stage of a Behringer DEQ2496 DAC/Equalizer unit.
Download: Dragon Boats (2496 Mono).dyf

Download Topsy (4416 Stereo).dyf (link is now fixed)

Download DummyTest(2496 Mono).dyf

(The 24/96 file "Dragon Boats" is provided courtesy of Barry Diament at Soundkeeper Recordings.  Discs with this music and other tracks may be purchased in DVD-V format (or CD) from (www.SoundkeeperRecordings.com). This high quality recording is of the acoustic band "Work of Art", off the track "Dragon Boats" from their release "Lift".)

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Green Sharpie Pen Treatment Test: This is a test of the infamous CD treatment tweak (where the edge of a CD is painted with a green Sharpie pen, said to greatly improve the sound).  Using a consumer level player's audio outputs, recorded at 24 bits and with the recorder's clock locked to the player's.  Try to guess what the Difference will sound like before listening to this one!
Download Green Pen Test.dyf