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High pitch ringing noise after amp install

204 Views 4 Replies 4 Participants Last post by  Joebiker
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.
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Year and model and version of stock audio system would help.
Is power to the amp coming from one place and ground from another place in the power distribution system? And are power and ground homed back to the same sources as the rest of the audio system?
Forgot to mention, the amp gain is all the way up. I know I know… however it is the only way to achieve no input clipping from the factory signal. If I back off the gain the noise goes away but it’s not loud enough to really listen to with the windows down on the highway. 100+ rms watts of power with 90+ db speakers, that shouldn’t be a problem. So I guess the new question is why does the amp have to be turned up so high to get the level of volume it’s supposed to do at half-2/3rds of gain? Is the factory signal just that bad and nothing can be done?
Try hooking the amp directly to the battery and the noise should disappear.
Every amp I ever installed had the same problem hooking the positive cable directly solved the
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