Audio ground isolation

I am building a spectrum analyzer circuit (which works awesome by the way!) and need to figure out how to isolate the audio ground. When I was testing the circuit on the breadboard, I was running the analyzer on the breadboard and it worked flawlessly with an input from a car stereo and a separate power supply. Once I made the circuit on perfboard and soldered it together, it worked as well from a separate power supply.

The problem arose when I installed the display. When I connected the power and audio ground to the same supply as the car stereo, the audio ground shorts the radio output and I get no audio. My question is, is there a way to isolate the audio ground so that the radio signal will not be shorted?

I am at work so I don't have my schematic available, but I am hoping I have given enough info.

The car audio has a bridge output and neither output can be grounded (you can blow the amp if you do). You should be able to see a signal though from one of audio outputs to power ground, at least sufficient for your spectrum analyzer circuit.

Hmmm, hadn't thought of that, I'll give it a try. Would be nice if it works, I was originally thinking of using an audio isolation transformer, but your method sounds much simpler. Thanks.