in my car i have had a 500w amp powering 2 10s for quite some time now but the other day i added a 100w amp for my 6x9s cause one of my deck channels stopped working but now there is a high pitched buzzing sound which usually means a bad ground so i bought some new stuff, ground distibutions block, 4gauge to a brace under the antenna behind the paneling, i sanded down all the paint till i got to metal and got a ring terminal and bolted it onto the brace. from the amps i have 8 guage to the distribution block. i ran a 8 guage wire from one of the spots on the dis. block to the negative battery terminal and i added a 12 guage wire from the headunit ground to that wire that goes to the battery that quieted the sound but its still there. when i unhook the small amp the noise is gone but i really dont think theres a ground issue i think its a problem with the amp. its a crappy old majestic 252. One of my friends said it might be from the ground being too close the power antenna motor, anyone have a better ground spot?

 

maybe its just the cheap amp. see if you can hook up another amp using the same wires and ground points of the current majestic. it could be that the ground connections INSIDE the amp are bad.

or check if your gain is set too high.

 

I doesnt sound like a grounding problem. Usually when something isnt grounded properly, you dont get noise at all and if you do its like a popping noise not a buzzing noise. Now I am only assuming that the buzzing noise is coming through the speakers and not from the amp itself. If this is the case, try replacing the RCA cables with ones that are shielded. The buzzing noise may be caused by the AC frequency of the alternator.

 

something that is not properly grounded can cause a buzzing noise like that. its its not grounded right, noise can be introduced to the system really easily.