John Dunlavy On "Cable Nonsense"

Testing is a good idea but no pratical computer test equipment has a noise floor exceeding 96 db. Our hearing has a dynamic range of about 110+ db. That makes our ears many times more sensitive that any test equipment. Chris

You can invert the polarity of one channel and measure accross the positive leeds at the speaker, with a mono source you will then be measutring the difference between channels. Then with different cables on each channel, you will be measuring only the difference caused by the cable and since the differences will be very low you can add amplification to bring the signal above the noise floor of your sound card. An intersting variation of this descrived by Hafler allows you to listen to the difference signal directly.

Sqjudge,
Can you suggest any components for doing this measuring and testing.
Only 96db sensitivity?
What about taking an A/D converter from someone like dcs which is really high quality and take the digital out of that and do the measurements?

Is there a PC interface for TOSLINK or ST link????

Trappist: The quick answer ... No I do not have any recomendations for equipment. The resolution om a 16 bit system mathamaticaly is around 86 db. It would be higher for a higher bit a/d converter but that is not the problem with making high accuracy measurements. Yhe problem is the noise floor of the analog front end of the converter. Therman noise and resistor noise (thermally related btw) would limit the actual resolution of the system. It would require cooling (like liquid nitrogen) to get the thermal noise low enough to get 110 db range accuratly. I do not believe a computer can be effeciently used in a near absolute zero enviroment. Chris

Thanks Chris. Clearly you're knowledgeable! Seems though that digital source equipment can't produce quality up to what we can hear, so we can probably measure at a similar quality level and get some meaningful results.

The dcs 904 will sample at 192 khz 24 bits.

But then of course, the cables could have such subtle effects that these measurements won't be meaningful. The differences I have heard with interconnects though lead me to think that they could be measured fairly easily. l liked lemme's idea of inverting channel polarity and comparing that way with different cables on each. Very clever.

Trappist.