I have an aftermarket head unit. I'm changing things around a bit. The unit takes two types of power directly from the battery and the ACC which turns on when the ignition is on. Both are 12 volts into the unit. After hours of searching I found out why I have absolutely horrendous feedback. I checked all the obvious things first, like the ground and wires crossed but it turns out it's the ACC. When I ran power directly from the battery, there was no feedback in the unit. Sounded great.

Any ideas on how to clean up the ACC power. Maybe I power it from another fuse or something.

I'm also wondering what is turning the power so dirty. But I be able to live without knowing if I can fix a darn thing.

 

darn, it is more insidious than I thought. If the ignition is on the noise gets into the system even if i run the power and the ACC trigger directly from the battery.

 

Can yo describe the sound or do a video. If its a whine varies with engine speed suspect alternator . Try a capacitor traditionally 3 uf from each 12v line to earth or and a choke in the cable. Or clamp one of those inductors onto it you get on USB cable .

If you have an antenna try disconnecting that.

 

So the feedback is coming from something in the engine. When the ignition is on (engine not started) and the stereo is not connected there is a hum/whine. The feedback from the stereo is the same frequency as the hum, but the hum is also amplified through the speakers.

I have two videos. The first is the hum with the stereo disconnected. The second is from inside the car and you can hear the original hum and then the amplified hum 16 seconds into the video.


Noise without stereo connected

Noise from inside - incudes with and without amplification

 

The hum from the engine is coming from the throttle body. I am not sure if that is what is creating feedback to my stereo, but the pitch it similar to maybe it is.

 

I have the same problem, but in my car the whining changes with rpm.
Problem started when I put in a new aftermarked Alpine head unit and new Alpine amplifier last summer.

 

From what i can tell your best bet is the Alternator Whine. google it, there is tons of info on that issue. Mine is very different. i also dont think mine is a ground loop, i hooked the head unit and the amp to the same ground and the issue is persisting.

 

Have you tried powering your head unit from an external power source (i.e. completely separate grounds and 12v)? That will tell you if the hum is coming through the powerline or is some kind of stray RF noise entering the head unit. Your chinesium head unit might not be particularly well shielded from RF interference.

BTW my throttle body doesn't make that noise.

 

I have had the same issue since putting in my aftermarket. Tried to figure it out but could not determine what it was. Mine does not change with RPMs. It is just there. I am thinking of just getting an AC filter. I had to do that for my X300.

 

There is a accessory connector behind the glovebox that will be powered if you put in a relay in the trunk fuse box. It is the second relay from the right (that normally is missing). This connector got its power directly from that relay and nothing else is connected to it (other than a similar connector besides the battery). Maybe that could help, if you know that the ACC power is the problem