From the manual -
NOTE: In Bridge-Mono mode, only the Channel 1 level control is functional.
This is not the only model or manufacturer that does this. The channel 2 level control can be set at 0 or at max - it doesn't matter.
Uh, sort of. From page 26...
BRG (Bridge-mono or Stereo): Use this option to set
the amplifi er to bridge-mono or stereo mode. When BRIDGE
is active, the Ch. 1 input signal is used (unless you made an
alternate setting with the Y processing block).
From page 25...
Y (Input Y): The options are
• CH1+CH2 (Ch.1 input signal and Ch. 2 input signal are
summed and fed to both output channels.) This provides a
6 dB level boost.
• INPUT Y (Ch. 1 input signal goes to Ch. 1 and Ch. 2
output. Ch. 2 input signal is ignored.)
• STEREO (Ch. 1 input goes to Ch. 1 output. Ch. 2 input
goes to Ch. 2 output.)
The way it defaults is this: blank preset, starting from scratch and going into OUTPUT BRG mode, the "Y" setting is stereo input; channel 2 physical input is ignored and external level knob is bypassed. This is how the "Y" option works, too. Only Channel 1 input and output processing is accessible but is applied internally to both channels.
Changing the "Y" selection changes the behavior of the Channel 2 external level knob and physical input. If you use the sum (A+B) input mode the physical connection and knob now work, but the input and output processing is still "one channel."
Crown doesn't put the puzzle together, but they at least provide all the pieces.
Have fun, good luck.