Bridging vs. mono

If a stereo amp has a power supply designed for 2 channels, it may not be as effective bridged. Some amps are better suited (some class A I believe) because of the design, but having the power supply optimized for one channel is the real advantage for dedicated mono amps.

I formerly owned a Mark Levinson 27.5 dual mono amp which
was excellent, but only 200 W/Chan @ 4 ohms, slightly
wimpy for my greedy Magnepan speakers. I thought about
purchasing a second 27.5 and bridging both, which would
give something like 500 W/Chan. I contacted Madrigal, and
they advised me that although bridging a stereo amp to
mono will increase power output, it does make it less
stable, and may be problematic if the speakers dip to
a low impedance over its range. The Levinson amp was
rated normally down to 2 ohms, but it would only work to
4 ohms when bridged. After hearing that from Madrigal, I
sold my 27.5 and purchased a 335 amp which is rated at
500 W/Chan @ 4 ohms, and sounds more dynamic on the
Magnepans.