In general, the "tape out," should be the best way to go. The volume control, any signal processing normally doesn't change anything using this output. The volume should stay at a fixed level, meaning the level shouldn't change using the "tape out", even if you change it on this Denon DRA75. The volume be controlled by your other preamp. Input selector would need to be set for phono, and the proper phono cartridge (MM/MC) type also.
The pre-out output normally would be for using the whole preamp, tone, volume, and input selector section of the unit, to feed an outboard power amp. All of the controls (just mentioned) change the outputs coming from these pre-outs. It's like a stand alone preamp this way.
Who knows what it could go through using any other outputs, without a manual. Can't seem to find one online.
The pre-out output normally would be for using the whole preamp, tone, volume, and input selector section of the unit, to feed an outboard power amp. All of the controls (just mentioned) change the outputs coming from these pre-outs. It's like a stand alone preamp this way.
Who knows what it could go through using any other outputs, without a manual. Can't seem to find one online.