[j3brow]

Originally Posted by tdelahanty

Your Mac amp (the 501 is not a fully balanced design) is indeed driving the REL sub. The REL speaker level connection is a high impedance load (basically voltage driven), therefore requiring very little current and no load to the amp.

Thanks tdelahanty!! I'm still trying to figure out how I need to hook my rel up properly. According to Mc website, the 501 circuit configuration is "quad balanced". Stereophile review of 501 says that it is a "double balanced push-pull" circuit. "each half of the amp is fully balanced from input to output". "Each phase rendered in balanced configuration". The only time I get hum with either my old 402 (quad balanced) or 501 amp is when I forget to turn off sub before I unplug the banana plug at the amp. Maybe I should just stick my head in sand and ignore but I don't want to damage the amp over time. It doesn't run hot per say but my amps are loafing at .5 to 5 watts about 98% of the time. To confuse matter further I have aftermarket cable which combines the 3-lead wire (red,black,yellow) into a standard two lead system ((I forget if its two hot and one ground or 1 hot and 2 ground ---- I presume it's 2 hots combined yellow and red??))