Strange ground loop problem.

[norbie]

I have a headunit, with two phonos going to an amplifier in the back of the car.
The amplifier is 2 channel, and powers my two rear speakers.
It has a ground loop isolator at the amplifier end, as without it I get major interference/feedback when the engine is on.

Today something has happened... For whatever reason the rear right speaker is very very quiet compared to the other speakers. I have checked the amp and headunit and all connectors seem fine. I swapped over the phonos into the amp to check it wasn't the speaker at fault, and the same effect happened on the left speaker instead this time (Speakers work fine).

I took the ground loop isolator out, and hey presto sound is restored to all speakers! Problem is I get that interference if I turn on the engine.

I tried another ground loop isolator as I had one spare thinking that was at fault - plugged it in, same problem again, one of the channels is very quiet.

As it works fine without ground loop isolator it cant be a dodgy connector somewhere.

Please say if you have any ideas?!!