How to go from RCA to XLR?

Thanks Al. The reason I suspect the amps are converted from a stereo design is because the tech sort of alludes to the theory. There's many high end mono amps out there that are done the same. I look back at Audio Research's Classic 60 and Classic 120s as an example. I'm not sure but I suspect the 60s were converted in a like manner. Krell's KSA 300 can be converted to mono in a similar fashion.

BAL-TX1 from space-tech-lab dot com.

Al, your descriptions and explanations are dead on.

Al, if truly balanced is achieved best with mirror imaged circuits, what better way is there than taking a stereo amp and letting one channel drive the positive signal and the other drive the negative? I know this seems like a simplistic approach but it should work maybe at the cost of low impedence drive.

Rww -- I'm not certain I understand your question, but I think you are asking why shouldn't all monoblock amps, at least the better ones that have balanced topologies, be designed as bridged amps.

I'm probably not the best person to give you a comprehensive answer on that, because although I am an experienced EE my professional background is primarily digital, not analog, and is unrelated to audio. But the basic point to bridging is, as I'm sure you realize, to increase output power capability. But that comes at the cost of the ability to drive low impedances, as you alluded to, and I'd imagine at the cost of a number of other conceivable distortion mechanisms. Off the top of my head that would include difficulty matching the two amplifier sections precisely in terms of many different parameters (gain, linearity, phase and frequency response), delay offsets between the inverted-polarity path and the non-inverted polarity path, etc.

And whatever the reasons may be, I think the conventional anecdotal wisdom is that more often than not bridged stereo amps often just don't sound as good as when those same amps are used in normal stereo mode.

Let me know if I misunderstood your question.

Regards,
-- Al