[SlimDevices: Audiophiles] What ever happened to the "AVX/AIX High-Resolution Test"?

[Archimago]

Hmmm, remember last year I did the 24-bit vs. 16-bit test here and on a
few forums. The 'results did not show significance'
(http://archimago.blogspot.ca/2014/06/24-bit-vs-16-bit-audio-test-part-ii.html)
for audiophiles being able to differentiate the two test signals.

Shortly later AVS paired with AIX ran a test:
http://www.avsforum.com/forum/91-audio-theory-setup-chat/1585994-avs-aix-high-resolution-audio-test-ready-set-go.html
and then a "version 2" because the samples were not volume matched:
http://www.avsforum.com/forum/91-audio-theory-setup-chat/1598417-avs-aix-high-resolution-audio-test-take-2-a.html

Did Scott Wilkinson (Mr. Home Theater Geek) give us a final report of
the results somewhere in the thread? The whole test was highly touted
including on places like AudioStream. I'd be interested because here's
an example of a 24/96 --> 16/44 where listeners could just load it up on
an audio editor and see the difference in frequency response between the
samples (hence why I limited the test on my blog to bitdepth).



Archimago's Musings: (archimago.blogspot.com) A 'more objective'
audiophile blog.
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[Archimago]

The second generation samples are grievously flawed in that the
resampled audio falls out of synch so badly with the original files that
http://www.hydrogenaud.io/forums/index.php?showtopic=107570&view=findpost&p=895219
I believe this was due to the fact that the resampling was done with an
outboard hardware resampler, rather than with software resampling. The
former is subject to clock drift, the latter generally not.
Credit where credit is due - I was tipped off to this exact problem by
M. Zilch (MZIL) who pointed this problem out months ago on AVS.

Thanks for the info Arny. Wow. That's unfortunate. So that I'm clear
since I didn't have a look at those files, did they actually also go
through a resampling step with AD/DA conversion thrown in?

I assume then that the test was abandoned and no final summary / data
came of it?



Archimago's Musings: (archimago.blogspot.com) A 'more objective'
audiophile blog.
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[arnyk]

Post by Archimago
Thanks for the info Arny. Wow. That's unfortunate. So that I'm clear
since I didn't have a look at those files, did they actually also go
through a resampling step with AD/DA conversion thrown in?

I don't think that the resampling involved any A<>D conversion.

The professional digital sample rate converters I'm familiar with are
typified by this device:

http://mytekdigital.com/storeeu/index.php/electronics/digital-cameras/stereo192src.html

18035

Notice that the devices inputs and outputs are AES/EBU - digital.

User manual: 'Mytek Digital Stereo192 SRC Sample Rate Converter User
Guide Link'
(http://mytekdigital.com/download_library/operation_instructions_stereo192src-english.pdf)

Typically they have two modes of operation - synchronous where the
output sample rate is a precise fraction of the input sample rate
(preferred) and asynchronous where the output sample rate is determined
by a separate external clock. The second mode of operation is sometimes
preferred because it may reduce jitter.

Speaking as someone who has tried to organize this kind of test,
avoiding distributing files that lead to false positives has been a
problem. I've produced files with this same failing in a different
context.

One of the problems with this kind of test has been pointed out in
papers describing tests done in the past, which is IM in the monitoring
system. I've been working for about a year with this issue, and from
that experience I have found that this problem is a lot more pervasive
then some people would like to admit, especially when it is their
monitoring system that may be at fault.

It is very disappointing to work hard to hear audible differences only
to find that they are not due to the issue that is the purpose of the
experiment.

Post by Archimago
I assume then that the test was abandoned and no final summary / data
came of it?

I find nothing I recognize as a final summary that includes the critical
issues that I am aware of. If anybody can find one, please help!


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