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Old 11th September 2012, 07:14 PM   #27551
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People can either hear these things with ears-only or they can't.
Some DBT get in the way.
Unless any give test show that it can produce also positive results, that test is meaningless and invalid.
The assumption that because of a test is blind it eliminates anything that may interfere with pure auditory perception that assumption isn't based, and at least in some cases I know of, is erroneous.
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Old 11th September 2012, 07:26 PM   #27552
dimitri is offline dimitri  United States
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Quote:
In any case, I will just go with what works, knowing that a null test will not give me any useful information.
Hello John, you mentioned many times that (Carver) null test doesn't provide any useful information. Meanwhile you and Walter Jung (TAA 4/85) had used null test for capacitor quality measurements. Does this mean that capacitor measurements weren't done in the proper way?
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Old 11th September 2012, 07:31 PM   #27553
SY is offline SY  United States
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Unless any give test show that it can produce also positive results, that test is meaningless and invalid.
But it does, as has been pointed out and linked about a million times. So instead of criticizing blindly (as it were), why not actually read some research papers?
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Old 11th September 2012, 07:54 PM   #27554
RNMarsh is offline RNMarsh  United States
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Default A lot of room for doubt --->

1. I was sent a mic preamp that a record producer said had noise in it.... could I fix it. I listened with headphones and didnt hear anything unusual. After a 1/2 hour phone call describing the quality and nature of the sound I was to hear and asking me to listen "deeper" after several attempts.... i finally did hear it. A low freq steady tone. (probably a ac line harmonic). Afterwards i heard it easily and always when I put on the headphones. It was subtle but it was there. Surely would not be heard in a dbt between mic preamps. It helps to listen Hard and long. But it helped me when I knew what I was expected to hear by another who had heard it.

2. Swedish Radio developed an elaborate listening methodology called "double-blind, triple stimulus, hidden reference". 60 "expert" listeners spanning 2 years and 20,000 evaluations finally concluded which codec was transparent and could be used.

A sample of the codec was sent to the late Bart Locantli - an acknowledged expert in digital audio and chairman of an ad hoc committee formed to independantly evaluate low bit-rate codecs. Locantli instantly identified an artifact of the codec. After Locantli informed the S.Radio of the artifact listeners at S.Radio also instantly heard the distortion.

Locantli used observational-listening technique which audiophiles routinely use. (this story is doc in AES pub).

I think it could be that Locantli knew what to listen for in artifacts of codecs before he startd to listen. Something he had heard before or learned from theory even (?)

F.Toole has shown in narrow tests for specific things what audiophiles have said for years- they can heard much lower than 1 db changes. they can hear much less than 1% thd. etc. Scientific tests do show positives.

There is plenty of room to doubt the results of many dbx test as the total answere for all time. Even on a scientific testing basis. -Thx RNm

Last edited by RNMarsh; 11th September 2012 at 08:11 PM.
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Old 11th September 2012, 07:54 PM   #27555
morinix is offline morinix  United States
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Old 11th September 2012, 08:40 PM   #27556
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I just don't read the 'right' research papers. I read papers on how to IMPROVE audio design, rather than to negate it.
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Old 11th September 2012, 08:44 PM   #27557
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Dimitri, I would think that a cap subtraction test WITH a measurable and significantly different residual, depending on most cap types, is DIFFERENT from an A , B or X test. Time itself seems to be used in a different way.
An amplifier subtraction test might be OK, but it would seem that much of the residual might be just artifacts of out of band phase and amplitude shift.
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Old 11th September 2012, 08:54 PM   #27558
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For a change of pace:
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Old 11th September 2012, 09:36 PM   #27559
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For a change of pace:
Hi John,
What is it?
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Old 12th September 2012, 12:20 AM   #27560
fas42 is online now fas42  Australia
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Quote:
Originally Posted by RNMarsh View Post
1. I was sent a mic preamp that a record producer said had noise in it.... could I fix it. I listened with headphones and didnt hear anything unusual. After a 1/2 hour phone call describing the quality and nature of the sound I was to hear and asking me to listen "deeper" after several attempts.... i finally did hear it. A low freq steady tone. (probably a ac line harmonic). Afterwards i heard it easily and always when I put on the headphones. It was subtle but it was there. Surely would not be heard in a dbt between mic preamps. It helps to listen Hard and long. But it helped me when I knew what I was expected to hear by another who had heard it.
And a lot of what really counts in achieving realistic sound is about this type of distortion, as in eliminating it. The simplistic DBT won't pick it, but if you're subjected to the adverse component being there continually, sooner or later it will be a glaring artifact, that will irritate until you get rid of it. Once you're aware, the mind rushes to check whether that element is still present when you switch on the system, and there, blast it!!, is the problem still!

These are the sort of anomalies that immediately identify sound as being hifi, rather than the real thing -- you know that the sound is not right, but you would be very hard pressed to precisely describe what gives the game away ... that is, unless you spent many years tracking down these nasties !

Frank
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