Using Mark Levinson No. 380 preamp output simultaneously

Thanks for all the help..
@willcycle why is it not ideal? I was actually  thinking  about running the balanced to my mids and highs, and use the rca for my woofers (biamp) since my amp for my woofers only has RCAs

It's not a good idea because it unbalances the balanced signal.  The single ended output is taken from the non-inverting balanced output.  If the two phases of the balanced output see different loads they are no longer balanced.

If you are using both outputs to drive a bi-amps system, the gain level between the single ended and XLR output will not be matched