Sounds like signal input issue to me. Unplug the rca cables from the amp and see if it still has the the low freq buzz. If it does, it's the board, if not, it's the rca's. You can also try hooking up a different speaker as well, although that def sounds like a signal issue. WAIT!! Do you have a factory head unit, and using a line level adapter to convert to RCA? If that is the case, move the line level adapter away from the speaker, to behind the radio.
Grabber Blue "Betty" 2012 V6 Six Speed, 3.55, BBK cai/throttle body, longtubes, x-pipe, axle back w/oem tips, Lugo Performance Dynotune, Zex 100 dry. I need factory v6 foglight housings, and the stock 11/12 gt grill with the light housings.