Thread: Need ideas for ground loop noise

Hello all, first post here. It's not carpc related, but pertains to hunting down noise.

I have a 2003 Mazda6 with a factory non-Bose system. I'm using the Sylfex Auxmod for an auxiliary input (connects to where the tape deck should go). It uses a 3.5mm jack for input. With nothing connected to the auxiliary input, there is no noise. With just a 3.5mm cable connected, no noise.

When I connect my XM receiver, there's some nasty ground loop alternator whine. Connecting my Harman Kardon Drive+Play iPod interface also results in some ground loop noise.

To solve this, I went the easy way out with a ground loop isolator. I bought the PAC SNI/35 from Crutchfield, which AFAIK is the only GLI that used 3.5mm connections. It actually works great on the XM unit. But when using it in conjunction with the Drive+Play, it eliminates all low-end frequencies. Like there's a steep high-pass filter set for 150 Hz.

I probably need to track the grounds down, one-by-one, but man is this frustrating. The Drive+Play is a really sweet unit (just received it as a gift last week) and it sucks to have to listen to either awful static or pretend I don't own a subwoofer.