I believe I asked something similar to this a while ago, but I believe I'm hearing different symptoms on this setup, so I'd like to ask again. Sorry!

In my current car, I play my music and podcasts via my G1. The audio plays over bluetooth, and is received by a Venturi Mini, which is always plugged in to the cigarette lighter (what is the term now that there's no actual cigarette lighter in there? should I call it a power outlet?).

Anyway, this is connected via stereo audio cable to the built-in AUX-in on the car's stereo.

With this setup, I'm getting the noise found in the attached file. My apologies for the bad quality and the weird format. I took it with my phone's sound recorder. The recording is fairly accurate though, except it's not quite that loud, I just turned it up so it would be audible.

Any idea what this is? I get no engine whine at all, and in fact nothing I do in the car seems to affect the sound. It does change, but usually just in that the next time I get in the car it'll be slightly different.

And yes, anything not plugged into the electrical socket sounds just fine. This also happens if I'm charging my phone any plug it directly into the AUX-in jack at the same time.

Your help would be really appreciated. I absolutely love this setup, but the sound is really hurting.

Ground loop? Cigarette lighter socket ground to the ground on the stereo I guess.

That's what I was wondering, but I wasn't sure if the absence of a whine changed that.

Anything I can do myself? Anything that can be done without getting into the dash?

After listening to your sound, and glancing at the Venturi Mini web site, I'm convinced that the sound is not a ground loop.

In order to have a ground loop, you need physical electrical connectivity between more than one device, each with its own power supply.

If I'm reading the web site correctly, the Venturi Mini is not physically connected to your stereo, nor is it physically connected to your phone. It works entirely with Bluetooth (input) and FM radio frequencies (output). So it can't be a ground loop.

I believe your problem is simple FM radio interference. Every solution I've seen that uses an FM transmitter to play music into your car stereo is complete crap, and is always beset by exactly these kinds of noise problems.

It could very well be the Android itself generating the interference, or any number of other things in the car. Does the Venturi Mini have an option to change which FM band it broadcasts on? If so, it might be worth experimenting with. You can also try re-orienting the location of the Venturi Mini, or the phone, in the cabin of the car and seeing if either of those alter the characteristics of the noise. (To alter the positon of the Venturi, you'd either need a cigarette lighter extension cable (I've actually seen these), or some other kind of 12v connection, or another cigarette lighter location in your car.)

The Venturi Mini can work over FM, but as you can imagine it doesn't sound very good. On the left-hand side of the device there's also audio in/out ports, so everything could be wired if I wanted. I'm using the audio out in my setup. I may try FM just because I can't imagine it'll sound worse that what I'm getting now.

Ah, then yes it could well be a ground loop.

You can eliminate the possibility of a ground loop by doing the thing you said you wanted to try: unplugging the audio out cable and switching to FM. The sound quality may be crap (or it may be decent, I dunno), but if the specific buzzing noise goes away when you unplug all cables and switch to FM, then you know it's a ground loop of some kind.

If the problem remains when you switch to FM, then the problem is either the Android inserting noise into the Bluetooth data stream (unlikely), or the circuitry on the Mini itself sucks and is inserting unnecessary noise into its output stage.

Just to be sure: The noise isn't there at all when the car stereo is just playing a CD, right?

Right. And yes, the noise goes away when using FM, but the audio quality is noticeably worse. It would probably be fine for podcasts, but I can't see using it for music.

Okay, then, time for the usual ground loop diagnostic.

Is your stereo an aftermarket stereo or the factory one? (I don't recall if you're still using an empeg?)

Either way, see if you can pop it out and wire the doohickey directly to the same wires that the stereo is powered by, with (just for experimentation's sake) the shortest wire run possible. Also see how short you can make the audio connection cable.

Also, just for ha-ha's: Um, is this the first device you've ever plugged into the Aux-in jack on the stereo? If it's the first, see if a different device (one that's not connected to the car's electrical system, such as a portable battery powered CD player, or the headphone jack on your cell phone) produces the same noise. If so, then the problem is still not a ground loop, but rather, a problem with the aux-in on the stereo.

The stereo is factory, and I'm certain that I wouldn't be able to pop it out myself.

I have tried going right into the Aux-in, and as you imagine I don't get the sound.