does output quality change when amp bridged?

When an amp is bridged it will generally deliver more power than when it is driven stereo into two similar impedance loads. For example one 8 ohm load bridged, vs two 4 ohm loads. This is because when bridged the two channels are operating out of phase so that when one channel pulls from the power supply plus voltage the other channel pulls from the minus voltage.

Also, distortion will not double. Distortion is expressed in percent, so the higher output offsets any higher distortion component. Furthermore, insofar as the distortion and noise is the same in both channels (common mode) for example hum, it will be eliminated in the bridged output.

Also...damping factor is reduced.

Dave

The amp does see a halving of the impedence when bridged, so if the amp isn't stable into half of the speakers impedence rating, you can have problems with the amp...especially when pushed hard. However, if your amp is stable into a 2 or 3 ohm load, you are likely good to go.

Doesn't impedance requirement of the speakers also increase? When I was using an NAD multi-channel bridgeable amp for home theater, I seem to recall that in the bridged mode, speakers with a minimum of 8 ohm impedance were required.

ive owned & ran the mc2102 in bridged mono & it sounded great,everything doubles in bridged mono,like wattage & distortion but doubling 0.005% distortion isnt going to give you any noticable difference in sound quality.

IMO amps that give up the goat when ran in bridged mono are poorly designed to begin with,the mc2102 is perfect for running in bridged mono with no ill affects in sound or performance.

the ss mac stuff bridges just fine.....the tube macs lose a bit of sweetness

Yes, for the worse...except with amps that are completely dual diffential (balanced) like Jeff Rowland.