What is the voltage gain of the Radius amplifiers?

Most are 26dB, some are 32dB.  The levels are adjusted internally with DSP as well, suggest more gain can be had by applying gain at the loudspeakers (+6dB or +10dB).

Anything that is bridged is 32dB, so the LF on RSX212L, RSX18, RSX18F, RSX218.  All other channels are 26db.