I've got a condition that's got me stumped. When our central HVAC ac compressor is running, my ACI Talisman speakers hum (the right speaker hums much louder than the left channel.) I have turned off the speaker's internal subwoofer amps, disconnected their power cords, turned off amp & preamp, turned off the power conditioner powering the cd player and phono preamp, and they still hum! I also tried letting a good period of time go by with everything powered off to let amp capacitors discharge, still hums with everything turned off. I'm not sure how long this has been going on, as it's a low level hum that you have to listen for. HVAC system is on it's own circuit in the breaker box shared with other ac circuits in the house.