I just finished wiring both amps into my vehicle but my sub amp has me stumped. I was setting the gains via DMM; starting with my main amp set to 17.3. I then moved on to the sub amp to do the same thing and can only get about 5 or so volts out of it at max gain???? I checked all connections and verified that nothing has been pinched or severed. Sitting right next to the sub you can barely hear it playing, even with the volume at around the 70% mark. Could bad RCA cables cause this? I thought if they were bad you wouldn't get a signal at all. Anything else I should look for?