Noisy PGA-04 loadbox...

I have a strange little problem with a used Palmer PGA-04 I got
recently. (It's a speaker emulator w/ a built-in 8-ohm load; handles
up to 120 watts rms. Transforms speaker-level output from an amp to
line-level.) I'm running a 100-watt guitar amp in, and everything
seems to work OK -- I get a nice, clean tone from the line-out.
However, the unit itself seems to be trying to act like a speaker! It
makes a very annoying noise that very obviously corresponds to the
signal coming in (i.e., I strike a chord on my guitar and it starts
buzzing). I opened it up and the sound appears to be coming from
around the area where there are 3 little 12V 75W halogen bulbs that
help dissipate power. There's some other circuitry and a little
transformer nearby also, so I can't really say for sure that it's the
bulbs. In any case, it is fairly loud. I can hear it from across the
room.

Which brings me to my question(s): can halogen lamps produce sound if
you run an audio signal through them? Is this normal? If not, are
there any other typical electronic components that can actually
produce sound this loud (if not working properly or something)? If
anybody else actually does have a PGA-04, does the same thing happen
on yours?

Any help appreciated, thanks!

 

Go to Google Groups and search for "magnetostriction" using
as the author.

Lord Valve
American

 

Ah that explains it. Thanks man.