Balanced and Unbalanced?

I was wondering if it is possible (read recommended) to run a CDP into an amp direct via balanced cables AND run an analog/preamp via the unbalanced connections to the same amp. In effect, both the balanced and unbalanced connections would be connected, only one would be in use at a time.

Wondering if there would be any negative effects to this setup. I was considering replacing my present SS pre with a tube preamp for the analog side to warm things up a bit. Curious if anybody else has given this a go. Also, if by mistake you did happen to run them both at the same time, would the amp effectively "add" the two signals together? Not looking to void any warranties here, just curious.

Related components:

Levinson 390s
Levinson 380
Levinson 332
Same story as the perennial question of whether you can connect 2 amps directly to the same speaker even if you use only one amp at a time. If you connect the two sources to an amp which lacks a selector switch to select bal/unbal, the two sources will shunt each others output even if only one is in use at a time. Even with the switch, which probably only changes the ground connection, this is not likely to be successful.

I suggest you ask Levinson before trying this.
Thanks for the input, I guess it would be as easy to unplug the other set when switching from analog to digital. Just curious.