As a new XH A1 owner with limited knowledge of some of the sophisticated audio capabilities of this camera, can someone explain the purpose of the XLR input selection switch (CH1 versus CH1.CH2)? In my particular case, I'm using an Audio Technica AT 835ST stereo microphone for capturing historic steam locomotives in action. I assume that the correct switch position for my usage is CH1.

Thank you for your assistance.

When you set it to CH1, the sound will be recorded on channel 1 *ONLY*; with the CH1+CH2 setting you'll get the (mono) audio on both.