Pioneer manufacturing defect

     Did you try grounding the outer part of your RCA cables?

     the shiny metal part you can see when the cable is plugged into your radio or your amp.

you can take a short length of wire ground one end to ground and strip a few inches off the other end  then wrap the wire around the patch cord and twist it like a bread tie     if this fixes your problem let me know and I can tell you how to repair the unit

No reason.  If it helped, leave it.  Pioneer heads are notorious for this defect.  I'd replace it if it was me... with a different brand.

I am writing in response to i am an idiot's post regarding grounding the rca cables.   I have a Pioneer DEH-P4600MP head unit... I have never had a problem with it until I recently tried installing it in my MR2.  I think what happened was... My ground on my amp came loose because I didn't crimp the ring terminal to the ground wire good.  Lesson learned... Always solder your connections.  Anyway, I am in car stereo feedback, buzzing, whining, popping (you name it) hell.... I have regrounded and re-routed every wire in every possible way you can imagine.

Anyway, to the point... I finally read the post about grounding the rca cables... I would've never thought of doing that.  But, out of desperation, I tried it and I couldn't believe it actually worked.  Thanks for getting me somewhere.  I was beginning to give up.  Well.. about 90%  of it is gone.  I can only here a slight buzz when the volume is off and it goes away as soon as I turn the volume up.

Now to the question.... am I screwed and have to buy a new headunit or can I fix this sucka?  You said something about a 1/4 amp fuse? can it be replaced or bi-passed?   Or do I have to solder 4 ground wires to each coax shield?  This sounds like an ugly band-aid.

Anyway thanks for any additional info.... and thanks for getting me to this point.