Like the title says, I have a 4 volt pre-out Alpine head unit and a refurbished Rockford Fosgate subwoofer amp. I have to turn the gain on the amp up to or very near the max to get a balanced output level with the coaxials running off the internal head unit amp. This is with the Subwoofer volume setting at around 7-11 out of 15 max on the head unit. I have a simple miltimeter but I was not able to detect *any* voltage out of the RCA outputs on the amp. I was able to read the voltage of the car battery so the meter seems to be fine. The analogue meter range goes down to 15 max volts AC or DC at its most sensitive, but I can't get the needle to budge on the RCA outs. I *know* that some power is being made there.
I assume that having to turn the gain up to max is not normal for a 4 volt pre-out. How can I properly diagnose my problem here?