The link to the review is posted on the Berkeley site, under the News page. Review is a rave. WDW
Wasn't asking for help....WDW@WDW... You must be wondering why Dan, Amir and I responded to your post about a review going up, and to each other, in the way we did. The main thing is that you'd like to learn, so here goes...
Basically, one of the most fundamental issues in making "digital" sound well is phase noise, meaning the accuracy of the clocking signals. If one uses a S/PDIF or AES interface, there are already a lot of issues. If the S/PDIF driving a DAC is in turn generated by a USB interface, there are even more issues. Phase noise analysis may also help visualize the possible origins of various types of time-domain jitter.
The Berkeley Audio Design alpha DAC is of course an iconic product, and the fellows behind it are both extraordinarily skilled and demanding, thus it took them a rather long time to finally evolve an interface that they thought was satisfactory.
So, one of the key problems any USB-S/PDIF interface designer has to solve is having an S/PDIF clock with very low jitter and phase noise, thus the possibly unexpected jump into a "deep dive" on that topic. From the perspective of, well, experts in this area, the sequence makes perfect sense, although not, perhaps, to more normal folk.
Thus, a simple announcement of the new interface immediately triggers a discussion about the arcana of phase noise and $70K DACs. And Amir raised the interesting observation that RH thought PCs sounded differently than Macs, which could be either a phase noise or a galvanic isolation issue. More discussion about obscure details ensued.
Some of us on the forum have worked together over the years, know each other well in other contexts, etc., thus the assumed context and offering of reports on how other USB-S/PDIF interfaces sound (Dan), Amir's remarks about differences between platforms, and my responses to Amir's and Dan's comments.
Ergo, all the posts in this thread so far are spot-on with respect to the interesting news that you posted, namely the first review of the long-anticipated advent of what imay well be one of the best 3-4 USB interfaces available out of a couple of dozen products.
Hope this helps!
Thanks for spotting that. Here is the copy of the review amongst other products in the new guide: http://media.avguide.com/Digital_Source_Components_Buyers_Guide.pdf. Once you open it, click on the alpha USB link.
The review is of course very positive although I was puzzled by him saying he found a difference between a PC and Mac source. The point of an asynchronous and isolated bridge is to eliminate such differences. I will have to ponder what remains to explain the differences Robert Harley perceived.
If I'm not mistaken, the two trials were between his Goodwin Zalwin/Korean based noise cancelled PC box and a run of the mill iMac.
To respond to your surprise of Harley's noticable preference a Mac before a PC server
, this was due to one major difference between these two platforms. The Mac was running Pure Music.
If an asynchronous USB device that is fully isolated doesn't remove the difference between PCs and Media Players on them, then there is some unknown science I can't explain .
Maybe he has PC set up so that it doesn't output bit-exact. That would make a difference. But if the PC is bit exact, then there should not be any difference as any timing difference would be taken care of by the USB to S/PDIF bridge.
Indeed, it would be bad news if the best hardware out there can't get rid of this difference. It means we don't really know what to do next!
Those features help when you don't have an asynchronous connection and the PC is generating timing. To the extent the Alpha is doing that now, it should not matter.
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