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Old 21st February 2014, 02:24 PM   #1
Mooly is offline Mooly  United Kingdom
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Default Listening Test... A Practical Demonstration That Amplifiers Have Their Own Sound.

This one is different, very different

What we have here is a recording made by taking the output directly from across the speaker terminals... in other words the real voltage from an amplifier as it appears across the speaker.

How do you listen and evaluate such a "test" ? Answer... I don't know. Are headphones a realistic option ? I suspect not because when I replay these through headphones the "effect" or differences are obscured to a large extent and don't come across. On speakers then ? Well probably. The two files are chalk and cheese when auditioned this way. Maybe "tests" done this way could be more revealing of how close an amp comes to a piece of wire than all conventional testing.

Two different amplifiers were used in the test. The listening level was "moderate" (but matched between amplifiers) and the speakers are B&W703's that have a 3ohm impedance minima.

https://www.dropbox.com/s/h74vg3x5i4qcf1z/RM1A.wav
https://www.dropbox.com/s/ssl4yuz1v66dgco/RM2A.wav

What are your impressions, I'd like to know
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Last edited by Mooly; 21st February 2014 at 07:47 PM. Reason: New link correcting channel reversal.
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Old 21st February 2014, 02:41 PM   #2
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The playback equipment, used when listening to wav#1 and wav#2, might obscure the differences (if any). I suppose the playback equipment might accentuate the differences (if any). Why not simply subtract the two waveforms and compare against zero? Or listen to the subtracted result?

If for example the playback equipment's "resolution" were 3 bits (SNR = 18 dB), it would obscure all differences.

Sorry if this is the 500th time the query has been raised.
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Old 21st February 2014, 03:04 PM   #3
jcx is offline jcx  United States
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and probably even higher count for for the explanation that the real conditionals attached to "all amps sound alike" is that they sound alike when they do give the same V at the speaker terminals

and recognizes that some amps do have audible output Z interaction with speaker loads and can sound different from other amps with different output Z with some speaker loads

the Carver/Stereophile Challenge is a clear example of matching "very different" amplifiers with output Z padding, minor feedback tweaks to eliminate audible differences in DBT listening
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Old 21st February 2014, 03:06 PM   #4
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by Mark Johnson View Post
The playback equipment, used when listening to wav#1 and wav#2, might obscure the differences (if any). I suppose the playback equipment might accentuate the differences (if any). Why not simply subtract the two waveforms and compare against zero? Or listen to the subtracted result?

If for example the playback equipment's "resolution" were 3 bits (SNR = 18 dB), it would obscure all differences.

Sorry if this is the 500th time the query has been raised.
Well, this is the problem... how do you evaluate what you hear in a test like this. Perhaps as a new test method there could be some validity in it though. If you have an original source and also the voltage across the real speaker then that is a golden opportunity to strive for the perfect amplifier... the piece of wire with gain. If the two defied reasonable differentiation then the amp has to be doing something right.

The two files in this thread were really an experiment... but I'm surprised just how different the sonic result of each is when played back via speakers. There is no subtlty here,the difference is huge. To say that amplifiers used within their performance envelope are broadly similar clearly isn't the case as this demonstrates.
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Old 21st February 2014, 03:13 PM   #5
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by jcx View Post
and probably even higher count for for the explanation that the real conditionals attached to "all amps sound alike" is that they sound alike when they do give the same V at the speaker terminals

and recognizes that some amps do have audible output Z interaction with speaker loads and can sound different from other amps with different output Z with some speaker loads

the Carver/Stereophile Challenge is a clear example of matching "very different" amplifiers with output Z padding, minor feedback tweaks to eliminate audible differences in DBT listening
That's a good point. By pure coincidence both amplifiers have 0.22 ohm series output resistors as standard. In practical terms that means that both should have essentially identical output impedances whatever the differences of the circuitry. The 0.22's would swamp those differences.
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Old 21st February 2014, 03:17 PM   #6
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on simple computer moniters, the first one sounds a little more forward in the midrange and seems to maintain itself s little better when the things get a little more complicated. The second seems to get a little compressed as things pick up. Just a drive by, as the speakers used to reproduce are less than ideal. I would say first amp is holding up a little better.
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Old 21st February 2014, 03:24 PM   #7
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by buzzforb View Post
on simple computer moniters, the first one sounds a little more forward in the midrange and seems to maintain itself s little better when the things get a little more complicated. The second seems to get a little compressed as things pick up. Just a drive by, as the speakers used to reproduce are less than ideal. I would say first amp is holding up a little better.
Thanks. They are certainly different.
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Old 21st February 2014, 03:27 PM   #8
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Ill have a listen on a slightly better system and see what I think. This is fun. Reproduced musical reproduction.
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Old 21st February 2014, 03:48 PM   #9
PMA is offline PMA  Europe
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A lot of fun Karl, thanks!
The difference is soo huuuuge in this test. I am posting a 10/10 ABX result, but would make 100/100 this time.

Briefly:totally different space. Voice is almost in the middle for RM1, but shifted right in RM2. Different tonality, different soundstage. What are those horrible power amps under test?

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Old 21st February 2014, 03:54 PM   #10
spiri is offline spiri  Austria
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It sounds like that the right and left channel are reversed on RM2.
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