High pitch ringing from full range dash after car amp install

[Noneill]

Recently had a Rockford Fosgate amp installed for my door speakers. Problem is that the amp is picking up electrical interference from somewhere and relaying it to the full ranges in the dash. A constant high pitch ringing noise. If I disconnect the inputs to the amp, the noise goes away. So it’s the signal not the amp. I’ve had this happen before on a previous vehicle with the same amp. The noise would stop if I turned off the DRLs. This time it’s not the DRLs and I can’t find anything that turns off the noise.

HOWEVER the noise does turn off when the vehicle is turned off for about 30 seconds but with all the audio and infotainment still running. Ground loop isolators didn’t work, different RCAs didn’t work, moving wires around didn’t work. Any thoughts or solutions?

Just to reiterate, SOMETHING is being turned off during those 30 seconds and that’s when it noise goes away. I just don’t know what.

[norman bates]

Usually, the rcA wires (line level) pick up noise when near power wires.

But I have no idea on this one.

[tomzarbo]

Trying to thunk of things that might turn off after 30 seconds or so... I think it lots of stuff that stays "on" for a bit after shutdown, and I guess that doesn't really help much. If isolated rcas didn't work, then it's probably coming through the power ground.

Can you powerthe amp via 12 v independent of the cars 12v system to confirm its the power side? Like a beefy power supply for instance?

I don't know if there is much you can do about that. Do you have another amp you can try to see if possibly another brand might not have the same issue?

TomZ

[Serenitynow]

Try sending signal to the amp from a mobile device using the headphone out jack to the amp RCA inputs. That will tell you if the RCAs in the vehicle are the culprit

Where is the amp located ? Grounded ?
Is it grounded to bare metal ( paint sanded off ) ?
Is anything else grounded at the same point ?
Is the headunit chassis grounded to the vehicle ?
Are the RCA output Jack's on the headunit grounded ?

I've encountered all of these scenarios causing problems with interference/ problems with the signal path in the past

[unclejunebug]

Recently had a Rockford Fosgate amp installed for my door speakers. Problem is that the amp is picking up electrical interference from somewhere and relaying it to the full ranges in the dash.

1. Do you have an aftermarket HU or are you running a stock HU?
2. If it's stock, what amp integration equipment is being used?
3. How many channels is this amplifier?
4. If it's more than 2 are there multiple RCA cables running to the amp or it is it one cable with 4 (or more) connectors?
5. If there are multiple RCA cables running to the amp are they running together?