Quote:Here's a little blurb. Link.
I have no doubt that ATI amps sound good, in whatever guise they are sold. I also get why bridged amps are necessary when higher power is needed than can be swung by a single-ended amp. But I always felt that if you could get sufficient power with a single-ended amp, that would be preferable to a bridge amp, all else being equal.
When two amp outputs are connected to the same load, in bridge configuration, several things occur:
--There are two noise sources added together, for a 3 dB higher noise floor. Presumably this is a non-issue since the preamp output noise will usually swamp out the amp's noise. Just stating for the record. The next items are more important.
--The output impedance doubles (damping factor cut in half).
--There are two sets of distortion components adding together. If they are identical, that's a 6 dB increase.
--Each amp sees half the speaker's impedance. This can often mean there's higher distortion. You can see this in Stereophile amp tests when they show power vs. distortion for 8/4/2 ohm loads. Example. Your 4 ohm speakers experience the distortion depicted in the 2-ohm curve.
All these factors are about the output stages and speakers, not about the balanced inputs where the common mode rejection helps kill induced hum/noise. That is indeed a benefit of fully balanced amps, but it is an equal benefit of single-ended amps with balanced inputs.
Many times in AVS Forums people have extra amp channels sitting idle, and want to bridge them "for more power." I tell them if the normal amp setup is never clipping, don't do it. Am I giving bad advice?