Which DAC is better?

I think by the word super, you meant "asynchronous"

Not all USB interfaces are designed alike. Most are synchronous, with the PC acting as the master clock. As you can imagine, the PC clocks are not the most ideal for for high end digital audio

Asynchronous creates a master clock outside and puts the PC as a slave for sending data. It results in less jitter. Most of the better async USB DACs tout this feature.

And if that's not confusing, enough, not all asynchronous USB interfaces are identical either.

I've had very good results with a Wavelength Wavelink USB interface vs an M2Tech Evo, despite both claiming an async interface.

One of the best USB interfaces I have used is the OffRamp.

Easy, Arye QB9.

Moon DACs are generally excellent - but that's their top of the line stuff. I just can't believe they would make their entry level sound any good.

Arcam should be taken out and shot for using words like "super USB" - I believe that's enough of a reason to avoid that DAC. Just think, a word like "super" has so much potential -- super coax, super Toslink, super FET, super bipolar, super feedback, super balanced, super Ethernet, super transformer. I suppose when a company runs out of design ideas, it could start adding "super" to everything in order to distinguish its mediocre product.

Chesebert - Is your assessment of the Moon DACs based on having heard one?

Sfar,

I have only heard their top of the line 750D (by itself, without comparing to my own or other DACs). I have not heard their entry level, but I can only assume it (I know I shouldn't) to be of significant lesser quality.

Any chance you can audition both DACs? QB9 does require some computer knowledge (non-trivial for high-quality USB sound) - I am sure your ayre dealer will be happy to walk you through setup procedures.

What about the W4S DAC2? a nice contender.