Home Theatre AM radio crossover

Sounds like inductive pickup of a nearby AM station ... the signal is strong enough at your location to drive the preamp section of your subwoofer. Try better-shielded hookup cables from the receiver to the sub.

You might also wanna call the engineering department of the radio station in question. Radio Engineers are generally pretty nice folks. Approached politely and respectfully, they very well might offer you some tips and help. As a last resort, and don't mention this to the engineering department on your first call, the FCC requires that a broadcaster take all reasonable steps to ensure the operation of the licensed transmitter causes no interference with other devices. Save that for later ... folks can get real testy when you go gettin' all legal on 'em from the go.

Thanks for the suggestions.

I already upgraded the audio and video connections at point of purchase - but the connection between the amp and sub is a Panasonic "factory" cable - (this isn't a high-end system) - and I don't think I'll be able to upgrade this one - although I'm open to suggestions.

Any other suggestions about how to "better-shield" the connection between the amp and sub before I make contact with the Radio station?

Thanks

Odds are a decent $20-class specific subwoofer interconnect will solve your problem.

The AM station must be nearby. Wires are acting like an antenna & picking up the AM transmissions. Rectification ("detection") of the RF signal may be taking place where there is non-linearity like an oxidised contact in a plug/socket.

PA equipment often picks up police / taxi type radio messages this way.

Try moving/changing some of the connecting wires to see if it changes. Also clean contacts on plugs etc.