strange feedback

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i was testing an amp i just got , when testing it i used 'kicker' twisted pair speaker wires , hooked up to a 6x9...

the amp did not have terminals , but wires...when i hooked the amp up to the twisted pair wires, i slit the twisted pair wire and pulled the insulation out about 1 centimeter, not off....and wrapped the amps wires around in a perpendicular fashion.

when i did this the amp made a humming noise, if i just wrapped it around loosely the noise would be weak, but if i actually squeeze on the wire tight the humming would become louder,

tightly wound the humming would stay and be very loud.

then i pulled the insulation completely off, and just twisted them together regularly....and there was no humming noise.

my question is...wtf? :confused: ... ive never had this happen
 
Was it close to the case of the amp? Or, it might have been 'defeating' the benefits of twisting the wires, maybe aligning one of the wires with the changing electromagnetic field from the other, at the worst angle and in just the wrong place.

EDIT: You weren't touching a wire with your fingers the whole time it was humming, were you?
 
Clipped said:
it made the noise whether i touched it or not... this is really weird.

the wires were close to the amp but, wired regularly it didnt make the noise, so i dont think this would effect it.

I'm not saying that I am sure that I know exactly what happened, there. But I AM sure that the wire's location and orientation versus the amp actually 'COULD' affect it (and definitely would, to some degree, even if that wasn't the dominant cause of the effect you noted, in this case), since both a conductor's orientation and location within a changing electromagnetic field do affect (and actually 'effect it', i.e. 'cause it', in this case) the current that is induced in the conductor by the field. (Check out some of the ramifications of 'Faraday's Law', and 'Maxwell's Equations'.)

This is also the reason why so many manufacturers' application notes say to keep wires perpendicular to a circuit board for a distance of at least a couple of inches, whenever a wire must enter or leave a board. It's the same reason why they also say that two wires that must cross each other should do so at a right angle to each other. It's to minimize cross-coupling (by not having the electromagnetic field from each wire induce current in the other wire, or at least induce as little as possible by not aligning the EM field with the other wire). Alignment/orientation definitely matters, for conductors in changing electromagnetic fields, as does distance/location from the field's source.

I guess you could just try repositioning and reshaping the wires, to see if you can make it happen again, to find out. I'm guessing that there's more chance of it happening close to the amp than farther away (i.e. It's less likely with the wires bent at a right angle but not near the amp). I'm guessing that when the wire was perpendicular to the other wire, it was in parallel with some EM field source within the amp (or maybe even on the chassis itself), such that a much larger current was induced in the wire than when it was not oriented like that.

Is the amp's chassis steel or aluminum (or something else)? I think that steel might be worse, for this effect, since it is a ferrous metal. Or I could be wrong and it's the opposite way. But neither steel nor aluminum is a very good shield for magnetic fields, even though they can both be pretty-good shields for electric fields. And a changing magnetic field induces currents in conductors. (The 'enclosed loop area' of the wires matters, too, but is not the whole story.)

Sorry to have blathered-on for so long, about all of that.
 
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