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Test your ears in my new ABX test
Test your ears in my new ABX test
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View Poll Results: Have you been able to discern the files in an ABX test?
Yes, I was able to discern the files and have positive result 3 20.00%
No, I was not able to discern the files in an ABX test 12 80.00%
Voters: 15. You may not vote on this poll

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Old 1st November 2017, 11:14 AM   #1
PMA is offline PMA  Europe
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Default Test your ears in my ABX test on crossover distortion

Hello friends, some time has passed and I have collected material for a new listening test. The files for download are at

http://pmacura.cz/ococ.zip

This time it should be a foobar abx test and my humble question for you is to download the files and make a foobar abx test and vote if you were able to discern the files in the abx test. Then please post a foobar protocol here.

At the moment, I would not like to disclose any details about the files under test and how they were created. I can only say that I believe that the final disclosure might be very interesting for all of you who care about audio chain quality.

Good luck!

================================================== ======================
Thursday morning, Nov 2

Let me say more about the test. There are two 44.1/16 files, on of them is original data from CD disc used in the test, the second file is recorded through this chain: Vincent CD-S3 player, 6m of coax SPDIF cable, DacMagic Plus D/A converter, power chip amplifier with OPA549, speakers Quadral Ascent 90, Roland Duo Capture Ex USB sound card for A/D recording. The two test files were matched in amplitude and time aligned at the beginning. The output for soundcard is taken from speaker terminals of the chip amplifier, the speakers are connected during the test. Voltage level is up to about 3Vrms at peaks. The chip amplifier has purely crossover distortion that lies 60 – 70dB below the signal magnitude (THD = 0.01% - 0.1% depending on magnitude and frequency). The crossover distortion has harmonics up to “infinity”, that means that both even and odd high order harmonics of distortion are present up to at least 200kHz at almost constant amplitude. I will show the spectral measurements later.
Attached is the test schematic.
=====================

Tuesday Nov 7

For those of you (and anyone who would like to participate again) who have complained on 16-bit resolution and music sample quality, I have prepared a new, much more "audiophile" test files at

http://pmacura.cz/toc549.zip

The files are in 48/24, the question is the same, please post your ABX result, but this time feel free to comment on your preferences and file sound impressions. Tested is track with and without the OPA549 amp (loopback vs. OPA549), loaded this time by 6.8 resistor, for the reason that recording with loud playing speaker is really annoying.
=======================

Friday Nov 10
As we were not able to discern the OPA549 distortion again, I asked Mooly to prepare this violin test through the simulated Texan. The latest Mooly's files for low biased simulated Texan are at:

low bias
Test your ears in my new ABX test
or directly
Dropbox - Low Bias Texan.zip

You are asked to listen to the files and post a Foobar ABX protocol, in case of a positive test result. The protocol should be the complete Foobar generated txt file with digital signature, for validity verification purposes.

===============

Nov 13
Speaker nonlinear distortion test files added
Test your ears in my new ABX test

Last edited by PMA; 13th November 2017 at 06:49 AM.
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Old 1st November 2017, 01:43 PM   #2
PMA is offline PMA  Europe
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Let me be the first to show the test result, 7/12, close to coin flipping .
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Old 1st November 2017, 04:44 PM   #3
PMA is offline PMA  Europe
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I have re-considered my opinion and I am disclosing that the test is on crossover distortion. Who can make a positive ABX result on this??
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Old 1st November 2017, 05:01 PM   #4
Pano is offline Pano  United States
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Test your ears in my new ABX test
Thanks for these Pavel. But for some reason Foobar ABX is not working for me under Windows 10. Is it a known problem, or just me?
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Old 1st November 2017, 05:35 PM   #5
PMA is offline PMA  Europe
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Hi Pano, I do not know, because I have WIN8.1. Have you tried foobar update? I had to do it when switching from XP to 8.1.

So, if ABX does not work for you, I will make an exception and ask you for your listening impression? As this is intended as ABX test, I do not think that comments might be a big problem. I will show the distortion profile after the test is over, that is in 2 weeks from now.
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Old 1st November 2017, 06:24 PM   #6
Pano is offline Pano  United States
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Test your ears in my new ABX test
Thanks Pavel. I did listen to both files, but I have a question: What is the source of these files? I ask because they both sound like they have dynamic loudness compression of a few dB. I compared them to the CD rip I have and that is certainly the case. Both have been peak limited, then reduced in volume. My rip sounds much more open.
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Old 1st November 2017, 06:34 PM   #7
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The source is 96/24 "hires" flac bought several years ago. And yes, nowadays almost all the files except for classical music have a kind of loudness equalization. The newer edition the worse. Moreover, one of the files is more or less "original" flac just resampled to 44.1/16 and level matched. This file was a source file for the distorted one. I am still waiting for some ABX results, because it is in fact the only answer I am interested in. People tend to have many impressions in uncontrolled tests that seem to disappear when the test is controlled.
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Old 1st November 2017, 06:37 PM   #8
Mooly is offline Mooly  United Kingdom
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Test your ears in my new ABX test
I've clean installed the latest Fall Creators Edition of W10 a couple of weeks back. Audacity, Foobar, all are installed however not all have been tested yet
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Old 1st November 2017, 06:39 PM   #9
Pano is offline Pano  United States
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Test your ears in my new ABX test
OK, well, hmmm. Not sure what to think. They sure don't sound like the files I have. Maybe in a recent remastering they pumped up the overall volume. Tho strangely, your files have peaks about 2dB lower than mine.

I'll try to get Foobar working again and do the test. I'm just not sure about these files, they seem odd.
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Old 1st November 2017, 06:47 PM   #10
PMA is offline PMA  Europe
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Quote:
Originally Posted by Pano View Post
Tho strangely, your files have peaks about 2dB lower than mine.
This is not strange but logical. The test files had to be matched in amplitude. If you want to find the difference in mastering against your files, then, please, measure DR of your file or show the time envelope. This would tell something about dynamic compression, maximum level tells absolutely nothing. The 96/24 Steely Dan files I bought are definitely dynamically compressed.

But once again, I would like to see ABX results.

Last edited by PMA; 1st November 2017 at 06:52 PM.
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