In Reply to: The BAS and the audibility of the ABX box posted by andy_c on March 7, 2008 at 16:07:37:
The only problem with Clark's story is that it never happened, and no one can tell when an ABX box is in the circuit. The line-level relays are a pure resistance of a couple of tenths of an ohm, in a circuit that is 10 kOhms or more from ground at the far end.
There is something he may be remembering, incorrectly. BAS member Micha Schattner and I discovered that the ABX high-current module, used for power amp switching (but not for line-level tests) and equipped with high-current speaker relays makes a soft mechanical clang that is different depending on whether A or B was being chosen. (This is referred to in the Lipshitz article also.) We tested the audibility of this with the relay module a few feet away from us and no signal in the system, in a very quiet room, and we could hear the difference. I don't remember the number of trials but it was 8 or 10 apiece, all correct, so there was no doubt we were hearing it.
This effect is irrelevant to ABX testing, for at least three reasons.
First, you can muffle that sound easily even with no music playing -- a couple pillows over the box and you can't hear it any more. Second,
with music playing you don't even have to muffle it (though I always
do); it's so soft that any music masks it. And third, neither this box
nor the reed relays used for line-level switching affect the audio
signal at all. If they did, you couldn't use them to test for the audibility of any subtle effects. This would make some subjectivists very happy and simplify their world greatly, but it isn't so. EBM
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Follow Ups
- RE: The BAS and the audibility of the ABX box - EBradMeyer 03/10/0812:52:46 03/10/08 (1)
- RE: The BAS and the audibility of the ABX box - morricab 05:12:30 03/11/08 (0)