I have a Cerwin Vega HT-S12A subwoofer that has begun making an
electronic distortion. The speaker itself seems fine when I do a push
pull and tap -- no voice coil rub. Just putting my hand near the
speaker causes a slight humming, however. The gain of the unit seems
OK, it gets pretty loud, but the louder you turn it the louder the
distortion gets. I've taken to turning the unit off because even when
it's getting no signal it will start to hum and buzz sometimes. Not a
60 cycle sounding hum, a buzzy distortion.

Any troubleshooting ideas?

Thanks and Happy Holidays!

Paul