The stock radio in my car has an RCA input hidden in the glove box.  I would like to continue using the stock radio, but would like to add bluetooth to the radio instead of using an RCA to Aux cable.  I had the BT-1A bluetooth receiver from parts express lying around the house, so I hooked it up to see how it would sound.  It sounds like there is a lot of interference playing through it.  How it is currently hooked up is just a cigarette lighter plugin to the bluetooth receiver and the RCA plugged into the stereo.  What do you think is probably causing this issue?

At first I thought it could be fixed using a ground loop isolator, but I have not tried this yet.  After reading some information on bluetooth receivers it appears there is a issue with the power needing an isolated DC/DC converter when it is using the same power supply.  Most people tend to use part MEE1S1205SC to remedy this.  I haven't used many bluetooth receivers in the past so this is all fairly new to me.

Any advice on what the problem may be/possible solution is greatly appreciated.

Does it only have noise in the car? Ie have you tried it on anything else?  May just be noisy.  Otherwise the noise culprit is usually ground unless of course in this case it is digital audio transmission noise.

I use the nvx Bluetooth to rca from nvx plugs into the cig lighter and cord runs to stereo. As far as your noise goes turn the car off from running and into the key on position and turn radio on. There shouldnt be interference to pickup.