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In Reply to: Re: Cable Test Method posted by john curl on November 18, 2002 at 14:45:10:
Hello John,That's amazing: 110dB below 50mV (about 160 nV)!! It is amazing to think that such a difference could make a difference to the perceived sound! I suppose you are you using a spectrum analyser for such a low level signal. Can you tell me more about the test method and signal you used or suggest.
I will understand fully if you cannot respond for commercial-in-confidence reasons. Thanks in advance.
HAVE FUN,
Follow Ups:
my receipe is get a pre-amp with a l-r setting, insert cable 'a' into one channel and cable 'b' into the other, play your favorite cd and crank the volume.
Hello Steve,That is a good method, but you would need to use a mono signal into both channels to be fair and you would of course have to listen, (not that I am adverse to music) ,but this opens the possibility for observer bias and will have others requiring that we use DBT techniques when the test results are presented for scientific review/publication. Your switching method is certainly a good way of getting around the problem of short auditory memory, without introducing extra circuitry. Thanks.
HAVE FUN,
JOEY.
Yes about the mono source, but the idea is to use left minus right mode of the preamp so only the differences are amplified, not toswitch between the channels. This elimates any need for dbt because you either hear an audible output or you don't.You can also connect this signal to your scope, pc based fft or whatever to analyze.
Hello Steve,I missed your point the first time, when you said l-r control. I interpretted this as your suggesting to use the balance control, hence my insistence on a mono source. It is now clear to me that you meant l-r (left MINUS right) in which case you should stick with a stereo source or you would have zero left MINUS right signal. Sorry about the confusion.
Now that you suggest the l-r option, you could build on this further and use the amplifier as a differential amplifier (exactly as I do with my oscilloscope differntial amplifier), by feeding the test signal or music to say the left input, via a T (double RCA adapter at the left input) and then connecting the cable under test between the left input T piece and right input. This with the amplifier set to left MINUS right, you could listen to the DIFFERENCE between cable input and output or view it on a scope. Unfortunately, the channels in the amplifier will probably not be matched well enough in gain and phase to make this possible. I will give it a try some time.
Thanks for your input.
HAVE FUN,
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