Input impedance of the preamp (or the amp if you're driving direct) doesn't change significantly with/without power on. But you must have the input selector switch set to the CD, otherwise there's no load terminating & no signal flow. I use an old cassette deck's inputs as dummy load for burn in. You can fabricate your own loads with cheap male RCA's & 1k-ohm R's from Radio Shaft, but why not run signal thru your cable simultaneously. My SS equipment is always powered on though (many threads on that).
