Radio feedback problems

Ive been installing raidos, amps etc a long time. Recantly ive been getting feedback problems in some cars and cant figure out y. It dosent happen right away but maybe after a week or 2 the cars get a high pitch hum when the engines running only. When the engines not running theres no sound. Ive tried noise emilinators and they help a little but doesnt clear up the total problem. Sometimes this happens through the headunit or last time it happened through an amp we had connected to the door speakers. If anyone has any info on Y this happens and how i can prevent it, that would be great. Also, when this does happen, how i can find out where the problem is

The majority of the time, this problem is due to one of two things: bad ground, or gain controls set too high.  There are other things, as mentioned above: performance ignition, battery level low, bad rectifiers in alternator, etc.My ex once told me I have a perfect face for radio.

I have the same problem, but It happens when my radio is off.  I turned down the gain but then I lost my bass.  How can I have bass and have the sound go awayFeed back from radio when key turned off.... I just added a sub and amp but when the radio is off I still get a voom noise from the speaker sub. What would cause this?

if it's hooked up properly, you shouldnt hear anything when the HU is turned off.... what did you connect the remote turn-on lead of your amp to?  the HU or Ign/Acc?Kevin Gerry

Certified Electronics Technician

MECP First Class Installer

Owner/Installer

Classic Car Audio

since 1979

I have the same problem.  I hear the noise when the car is off and the ignition is turned back with the radio off.  I turned down the gain to make it go away, but now I have harly any bass.  That sucks.  What can be done to make this go away.  I just want my bass with no more noise.....Feed back from radio when key turned off.... I just added a sub and amp but when the radio is off I still get a voom noise from the speaker sub. What would cause this?