@GingerBeard
The A and B speaker terminals on the RA180 share the same internal amplifier circuitry and are not electrically isolated from one another. They are designed to allow for speaker switching (e.g., between two sets of speakers), not for simultaneous connection to the same speaker.
Connecting both A and B zones to the same speaker at the same time may create a ground loop or impedance mismatch, which could potentially cause damage to the amplifier or the speakers. We strongly advise not wiring both outputs to the same speaker terminals, even if only one zone is active.
If you’d like to A/B test cables or connections, we recommend doing so one at a time, fully disconnecting one set before connecting the other.