Originally Posted by A Y
Wrong. Interconnects are mostly shielded. Most speaker cables are not. Speaker cables don't need shielding because the signal levels (30V rail-to-rail, and single-digit Amperage) are much higher, and impedances lower. Also, shielded speaker cables don't make sense for the same reason shielded power cables don't make sense: there are huge holes in the shield at either end of the cable. Most speakers are wood, and the binding post interface to an amp is pretty open. Huntsman, when you saw power line harmonics in your FFT, what were you measuring? --Andre
Thank you -- I didn't know the voltages were that high (actually, I had no idea whatsoever). My measurements were of the output from a very sensitive transducer that has 100mV full scale output, and as they are in an industrial environment they are subject to a host of noise sources -- inductive, capacitive, magnetic, and conductive -- the whole works. The single ended, unshielded cables were pretty susceptible, but I have the more sensitive xducers connected via differential inputs, running through shielded cable. Still had 60hz harmonics until I tracked down the pesky ground loop. This stuff is new to me, not my field, so apologies if my language is off. Are you an EE? You speak like one.
Originally Posted by Artisan Fan
I would also add that geometry and stranding can act as a natural shield in some cases.
I acknowledge that I don't know a lot about this stuff, but I do know that's not true. A shield 'intercepts' as it were, interfering signals that would otherwise strike yous signal cables, and conducts them to ground. If the signal cables are carrying those signals they are muddying your source, period. The best geometry and stranding can due is to balance the noise across the conductors in such a way that it is common to both, and then is rejected by the processing equipment. That's not shielding. ~ H