Hi Joe and Pmkap,
Yes, I saw rljones' posts, but as you say he notices the same without giving much more of an explanation.
Here is my situation: The ones I have heard are both car amps. The one I have now is an Optimus (Radio Shack) four channel amp bridgable to two channel with a real (RMS) power output of about 250 watts per channel into 4 ohms (they claim 400). The other one I tried was a Jensen, also with about 200 watts bridgable into 4 ohms. They both also have a truly balanced inverter stage, like rljones has.
Both sonded very close, with the Jensen sounding a bit metallic on the high end. On the other hand, I did modify the Optimus by replacing the 4558 op-amps with TLO82 Bifet op amps, and using 18 gauge wiring from the power supply rails right to the output transistors, and 16 gauge wire from the power resistors of the output transistors to the binding posts for the speakers.
However, both also sounded very close to... and don't cringe folks... a tube amp!
So, I have difficulty with one of your thoughts, not because you are wrong, but because I don't understand:
"Potential advantages of bridged operation:
* Cancellation of even order distortion products"
How, since the amp is pretty much all odd order harmonics. Differential input and complementary symmetry output all but eliminates all even order harmonics? Bridging, if it eliminates the rest, should sound hard and sterile, not smooth, revealing and sweet like it does.
If that is the case, then a good tube amp is more linear than a good solid state amp... yet measured distortion figures say that tube amps produce even ordered distortion, even in push pull amplifiers, where a good SS amp can have virtually no distortion.
You Wrote:
Potential drawbacks of bridged operation:
* Increased risk of overcurrent damage to output section
The Optimus amplifier has current limiting at the output stages. Presumably, the design engineer took this into consideration when choosing output transistors. The ones in this amp are rated for 25 amps. The amp may put out 17 into 4 ohms bridged. If that is the current limiter doesn't kick in way before then.
I am going to do some bench tests in the near future to take a closer look into this. It is fascinating that bridging would make an OK sounding SS amp into a truly wonderful sounding one.
Thanks!
Gabe