noise after amp install

[OneLethal87GN]

I had a friend of mine help me install a cd player, amp, and speakers in my g/f's car. We keep getting a humming noise through the speakers. He tried several different things to solve this problem to no avail. He tried different amps and the same noise. He finally put another amp in and played with it and finally got it to work. He never went back to try her amp one last time though. He says it's the amp. I got the amp brand new off Ebay. I know some of you must have had this problem at some point in time. What causes this and how do you fix it?

 

[mcss383]

is it a noise that varies with engine rpm?

A bad amp can hum, but the fact that you said a couple different amps did it, I doubt its the amp thats bad.

What amp is it? What guage power/ground wire are you using, how are those wires routed? Where is the gain set on the amp? Where do you have the ground wire grounded? Did you scrape paint/gunk off of where you mounted the ground wire so the terminal is touching clean metal?

All these Q's need answering to narrow down what could possibly be causing the hum.

 

[OneLethal87GN]

Her amp is a brand new American Legacy 240w amp. We tried a few other amps but I can't remember the names of them. We used a wiring kit from Wal-Mart that is for 300 watt amps. I believe it has 8 gauge wiring. After he messed around with the last amp a while he got the noise to stop. We never went back and tried her amp again though. The amp is wired using one hot wire from the pos. battery post, a ground to a bolt in the trunk, and the blue wire to the antenna wire from the radio. He tried running another wire from the neg. side of the battery to the amp but still got either the noise or no sound at all. We did have to play with the ground a few times to get it to work. The noise is at idle and with the car off, ignition on. The gain was turned up and down with the same effect.

 

[GNandTTA]

The noise is at idle and with the car off, ignition on.

So the car is off and ignition on. It must be a humming sound then not a whine sound. Ground loop will do that. EMR too. What kind of radio? I know its alot of work but to solve the noise you need to pinpoint the problem. Couple of options here. Get a boom box that has RCA inputs. This will determine if there is indeed a ground loop. Connect the RCA outputs of the radio to the boom box in the trunk and get a pair of headphones. Crank the volume up on the boom box and make sure the volume is all the way down on the radio. Still noise? If not than more than likely the radio is clean. Still another option is to get another radio and power it from inside the trunk. Connect the RCA's from the radio to the amp. Short pair if possible. Still have noise? If you do, than the amp or the installation of the amp is the problem. Often times if you have a wire that carries a large amount of current the noise can leak into the RCA if they are close enough. Often just moving the RCA's will get rid of it. HTH