I just replaced by sub amp with an amp that puts out double the power. To take advantage of this new power, and match the amps, I turned up my door speaker amp's level input to ¾ of a turn. A full turn is the max setting. Now I can faintly hear some white noise in the speakers when the car is off. I really don't know what DB level it is so I'll try to describe the noise level. If I leave the car off, empeg on pause and the windows and doors open I can barely hear the noise while standing at the front right or left of the car. If I walk to the center of the hood I can no longer hear it. Sitting in the car I can hear it when the car is not running and the volume is at a fairly low level.

After doing some investigation it looks like the noise is generated by the amp. The only other source might be the power line. Going to check that tonight.

Am I being too picky? Do all amps put out this type of noise?

The amps involved are:

Sub - US Acoustics USG3000D - 400 Watts x 1ch @ 4 ohms
Door - US Acoustics USG4080 - 50 Watts x 4ch @ 4ohms

All amps have a noise floor, but it sounds like you're describing something other than noise floor. You should not be able to hear the noise floor of your typical amp when standing outside the car.

Most likely what you're hearing is a ground loop.

A typical amp's noise floor is going to sound like a very very faint hiss, like wind through trees. Noise floor will not be "colored" at all, it will just be a dry hiss that is steady and does not change. A ground loop, on the other hand, will often have a character to it, like a pitch or a note, and may change over time.

Thanks, my last hope is that it’s a ground loop on the power cable. I petty well eliminated everything else. It does sound like a hiss but I can detect a slight change when I move the amp. I'm going to hook a separate battery up to the amp right next to it to see if the noise reduces some. The power line is running next to the wiring harness. This did cause some noise in the RCA cables so I moved them. I might need to move the power cable too.

I've been looking for a filter that would hang off the power line and eliminate the noise. But all I can find are inline power filters and I'm afraid they might not handle the current.

Hi

First I guess you unplugged the EMPEG at the amps to prove the amps were the source of the noise.

The second thing is: Are the speakers' negative terminals grounded at the doors as this will lead to problems and if so use the negative connection at the amp.

The third thing is to look at the amplifier main supply ground (while the EMPEG is unplugged) as the quality of that is as important as the positive supply. You are hoping the noise will go away with a high quality ground connection.

Lastly and most likely, If your amp is running bridged into two channels then common mode voltage between the amp channels can cause noise. Select 4CH mode and if the noise dissapears then great. Sort of great, as there is design fault in the amp so choose another.
Experiments with common mode voltage
1)shorting the amp inputs together negative to positive - should remove the noise
2)shorting the centre input to the EMPEG ground - will make some small amount of noise

(Common Mode voltage: parasitic voltage between the two bridging amplifier inputs. It will create an unwanted audible signal even with no input in bridged mode, but not in 4CH mode. The sound may change up and down with the battery voltage or may be static.)

Cheers

Thanks estocks. I still have noise and here’s what I have:

It’s a 4 ch amp with no bridge and four Infinity Kappa component speakers. I’ve run 12 gauge wire to the speakers and there is no chassis grounding on the speaker wires. The + power cable is 4 gauge copper. The ground wire is a very short 4 gauge copper wire grounding to the floor pan.

With no input connecter and all, and the sub amp disconnected as well, I still get noise through the speakers. I’ve tried powering the amp with a different battery totally disconnected from the car and sitting right next to the amp. This was even noisier than when it was connected to the car battery.

The only other option I see is that the noise is coming from the speaker wires. I’ve read that that is not usually the case. The only thing I can think to try is to hook up separate speakers to see if the noise goes away. Maybe I’ll first try disconnecting the front speakers as they run next to some of the cars wiring.