Sub amp humming issue

[dyazdani]

I recently sold my Bag End Infrasub 18 and the new owner is reporting a hum coming from the amp. It was not there in my system so I am trying to troubleshoot possible causes.

He says it is there "even without hooking it up to the preamp."

I suggested trying another wall outlet and hooking it up to the rest of his system in an attempt to isolate something.

Anyone have any ideas? I've never heard a hum coming directly from any components before, only the usual ground loop issues coming through speakers.

[Kevin P]

Is the hum coming from the amp itself or the sub driver?

If it's the driver, it could be a ground loop, interference or a bad capacitor in the power supply.

If it's coming from the amp itself, it could be the transformer or power supply. Is it a plate amp in the sub? Are all the screws tight?

[dyazdani]

Is the hum coming from the amp itself or the sub driver?

If it's the driver, it could be a ground loop, interference or a bad capacitor in the power supply.

If it's coming from the amp itself, it could be the transformer or power supply. Is it a plate amp in the sub? Are all the screws tight?

He says it is the amp, but I will verify the next time I hear from him. What I don't understand is that it did not have any issues when it left my system, but now it does.

Yes, it is a plate amp.

The other thing I wonder is if the hum is in the system somewhere. The LF integrater (aka EQ, filter) will amplify any LF hum in the signal. If he didn't have anything hooked up, who knows.

He does have another sub identical to the one I sold him, and he says there is no problem there.