How to hook up 2 amps?
The RCA cables have a shield over the signal lead that is grounded at the source - when you link two amps together via RCAs you are also linking their grounds. So if the impedance(resistance) to the amplifier's true ground (the wires you run to the chasis from the - post) is significantly different, the alternator will produce noise between the two amps.
The longer the RCA wires, the more aluminum shield there is protecting the signal lead. The aluminum is meant to reject emi from other electronic components and RF in the air from your signal (to keep it from getting amplified) but if you have excessively long RCAs, the aluminum shield will actually act as an antenna and gather up all the EMI and in turn the signal lead will send that EMI to the amplifier.
Cliffnotes:
Long RCAs make alternator hum and introduce static into your signal.
roger.



