Ok
@gene responded. My basic understanding was correct, though he indicated that the term does have specific meaning.
Ok so a differential balanced circuit only requires two mono dacs, each operated in antiphase to each other. You would then have positive phase, negative phase, and ground on a balanced connection. This canceled differential noise, but does nothing to lower the noise and distortion of the DAC.
Paralleling DAC's lower the noise and distortion of a DAC by about 40%, or so they say. There is a good argument to be made that we are talking about going from inaudible distortion to further inaudible distortion. Same with noise. Still, who doesn't like a technical marvel, in which the noise and distortion exceed any chance of being audible?
So in the case of the Denon processor that Gene tested, that unit uses a very high quality BurrBrown DAC in dual differential mode, which meant in this case that each phase bank had a pair of paralleled dacs. This ensures the lowest possible noise.
Gene made mention of some products operating in quad differential mode which, in that case, likely means 4 dac's paralleled together for the lowest possible noise and distortion organized in a differential pair with another quad block.
So I guess what we want to know about the Monoprice at this point is how many dac's per channel are used and how are they setup. The top of the line Datasatuses four of the best DAC's in existence per channel in this "dual differential" mode. a pair of paralleled dacs per phase per channel.
I can't wait to find out what is in this Monoprice. My guess is something not as fancy, it would probably be too expensive. The BB DAC used in the top Datasat is largely only used in pro audio gear. I don't think it's used in any consumer gear, but that may be wrong.