Are both outputs active full time? That way one can run, let’s say, the RCA out with a “y-Cable” for mono records and the balanced for stereo. Just hook each output to a different pre input?
Yes, both outputs active simultaneously.
In my system I run XLR to my GCD and RCA to my integrated tube amp
Yes, shouldn’t be a problem. Similar to the DSD and GDAC having both single ended and balanced, using both at the same time shouldn’t be a problem. Listen to the system though to make sure everything sounds fine. If there is an impedance mismatch, you’ll know immediately.
Do not “sum” the RCA outputs with a y-cable into one cable. You can damage things. If the device needs to output a mono signal in a two channel system it will send the same signal to both L & R outputs.
Nope. Y cable out to a single cable , then y in on pre is a normal method of doing such.