If you have two inputs on your sub use them both. If not I don't think it matters if you use the left or right out on your A 21+/A23+. I don't think the sub is in stereo.I run my sub thru my parasound pre amp.
connecting subwoofer to parasound via loop output on A21+ / A23+ ?
Can anybody advise if the signal to the sub is summed, or do I need to connect both outputs to my sub?
their manual shows the following;
Loop Output Jacks
These jacks enable the incoming audio signal to pass along or “daisy chain” from the Left and Right
Input jacks to an additional amplifier or powered subwoofe