- Posted by jneutron (A) on March 26, 2004 at 15:26:09
In Reply to: Nope, not the amp. posted by Bruce from DC on March 24, 2004 at 08:38:41:
I know, I know..keep my day job...:-)Two possibilities exist..Either e-field pickup, or m field.
E field would require very large fields to couple enough to make it audible..So I would rule that out.
So, where is the M field?
In the wall wires are usually parallel, non twisted, so they radiate a dipole field...strongest nearer the wire.
The speaker has internal loops, like the woofer litz wires. But you said moving the wire changed it.
The only way m field can couple to produce hum is if the amp impedance at the output terminals is not too high...that completes a loop...
You're speakers must be pretty efficient..
Do you have more than one speaker connected to the terminal?
With the wire in the place position to produce the most hum, get an old speaker magnet or a good piece of magnetic iron...or even a good horshoe type magnet, like the ones to pick boat motors from the lake..
Use the iron or whatever, to enhance the field near the wire...run the iron along the wire, listening for louder hum...If that happens, the source of the field is there.
If you twist the speaker run tightly, it should stop hum pickup.
I'm dyin to know what you find.
BTW, I'd have seen this interesting problem earlier if ya posted on prophead..I don't normally look here..
Cheers, John
