Hey thanks I'll break out the meter and try that!The following is from a friend on another forum:
"If the RCA shields for the left and right channels are directly connnected (~0 ohms between them -- with no RCA signal cables plugged in), they are NOT fully balanced.
You need to be careful when driving a strong signal (speaker level or preamp level from a source with a ±15v supply) into the input of an amplifier. If the amp is off or shuts down for some reason and the signal drives the input of the front-end op-amps above the power supply input of the op-amp (which is essentially at 0v since the amp has shut down), the front-end op-amps can be damaged.
Some balanced inputs REQUIRE a dedicated ground connection between the signal source and the amp. Without it, the amp may oscillate which could cause damage to the amp or to the speakers. Always monitor the output of all channels of the amp with a scope when experimenting".
I could not find any info as to wether or not the MB Quart RAA series amps can take a balnced input but you can measure between the left and right RCA's as noted above to check.:thumbsup: