Ground loop with USA-Spec DF-HON adapter

[haveblue]

I'm running a USA-Spec DF-HON adapter and there's a both an rpm-based whine and a (much more annoying) beep that happens every few seconds whenever it's being used.

This happens both whens the mp3 player is plugged in and unplugged. When listening to radio, there is no ground loop at all. I installed a ground loop isolator between the adapter and the mp3 player, and that did nothing, so it must be something between the adapter and the stereo.

What can I do? I can't really change the ground on the adapter, since it plugs into the stereo with an all-inclusive cable.

 

[Coconut]

Is the adapter plugged into the stock headunit, rear bulkhead area or trunk where the CD changer used to be?

 

[haveblue]

I don't know what it's plugged into. Previous owner did the install. Looks like it's going into that big OEM cable bundle back there. Which location does that lead to?

Tried my friend's iPod and it worked fine without a ground loop. But using the RCA, non-iPod, option, it's always there, even when the adapter is by itself without any RCAs attached to it. I have tried all 4 combinations of switch positions, and the two combinations that allow the RCA to play both make the group loop noise.

 

[BTL3.0]

it seems as though ive been reading bout ground loop with the usa-spec adapter. i have the Grom adapter for over 2yrs and no issue. i've used my ipod on it, lately i hook up a 3.5mm jack so i can use my phone to stream music.. it works and no ground loop noise..

 

[haveblue]

Is your hooked up to the same cable that mine is hooked to in the above picture?

 

[BTL3.0]

Both. First i had it like the picture u posted. Then i removed the console and mounted directly behind the stock radio. I have no cd changer. Removed n sold it already.

 

[haveblue]

Ah, so the way I have it set up, it's going to my CD changer? So you had a group loop noise when hooked up to both?

 

[BTL3.0]

Nope. Never had any noise.