I have a stock headunit with balanced outputs. I originally had it hooked up to my new amp by just running the wires from the factory amp straight to their corresponding places. Everything worked fine, but it distorted at about 60% with the gains all the way down. I measured the voltage of the headunit's preamp output and it was 10 volts - double what my JL XD700/5 supposedly can handle.
I set out to bring it down a bit, and I originally built a resistor divider array for each channel. It worked, but I posted a question on Stack Exchange about it, and an audio engineer told me it's not the proper way to handle balanced outputs - I could blow up my amp. So I run to the store and overpay for a balanced to unbalanced converter and voltage reducer. I wire it up, and now I have a low frequency humm when the volume is turned all the way down. I tried adding a 100k resistor between each of the channels ground and output, but it didn't solve the humm at all.
I say forget it, and turn on the truck. I hear alternator wine - I must have a ground loop problem, considering the grounding is really weird in the first place for balanced to unbalanced. Awesome, easy fix! I was on my way a few exits down the highway. Well, I had it up about half way, doing about 75 - and I see the "check guages" light come on. OH **** MY CHARGING VOLTAGE IS AT 18 VOLTS WHAT THE ****. Quickly popped the truck into neutral and turned it off. Pulled over, made sure nothing was bad.. and turned the truck back on. It stayed at 14 volts and I haven't been able to replicate that.
Does anyone know what these symptoms could be? Simple ground loop, or something insane?