I have a suggestion for Bifrost and Gungnir owners who have done the gen 2 USB upgrade. I realize this thread is for the Uber upgrade but there is no thread specific to the USB upgrade and many of you who did the Uber upgrade did the USB upgrade too. I have a Bifrost Uber I recently upgraded myself but it doesn't have a USB board.
I stumbled into something that may provide an improvement on the gen 2 USB performance. As a disclaimer up front I admit that I don't know 100% for certain this will work on a Schiit gen 2 USB board but I have proven it to myself with similar base components.
The gist of it: Try one of the ADuM4160 USB isolators in line between the computer and the gen 2 USB input on your Schiit DAC.
Further information based on my experience: The ADuM4160 device may not work with the original USB board using the CM6631 receiver chip. My experience is with an inexpensive Chinese USB to S/PDIF converter (feeding a Bifrost Uber) that uses the CM6631A receiver as is used in the gen 2 USB board. I looked around tech forums on the web and I found no indication that the ADuM isolator has been used with either the CM6631 or the newer CM6631A. I assume (ass-u-me) it's because the ADuM may be incompatible with the earlier chip and because of it nobody has tried it with the newer chip. FWIW, I emailed Jason at Schiit about my discovery and he told me they are aware of the effects and he was obligated to not discuss details. The ADuM isolator apparently does not work with XMOS USB inputs.
I purchased a couple of cheap async USB-S/PDIF converters using the latest revisions of the XMOS and C-Media receivers because I wanted to see how inexpensive cutting edge asynchronous tech held up against my Off-Ramp 3 that uses Steve Nugent's final generation design of adaptive USB (before moving to async USB). Neither of the cheap converters performed as well as the older and much more expensive Off-Ramp. The cheap converters both sounded slightly veiled and sterile but they did exhibit half decent stereo reproduction to some degree.
I read a recent article at CA by a guy in Poland who compared most of the current high end USB to S/PDIF converters. In the article the author spent time tracing the circuit in an absolute top end Berkley converter. In the back end of their USB circuit there is (what he believes is) an ADuM isolator. It can't be the ADuM4160 because it's designed for USB protocol. The chip in the Berkley is isolating whatever information has been decoded from the USB circuit. All that aside, it served to remind me that I had one of the ADuM4160 isolators I got a few years ago to try with the Off-Ramp. Ruined the performance and the ADuM got stored.
I dug out the ADuM and put it in line between my Windows OS music server and the cheap CM6631A converter. Immediately there was a heavy veil removed and the stereo image became MUCH more holographic on the Bifrost Uber. Significantly better than with the Off-Ramp, but that's not to say the Off-Ramp isn't more precise with its characteristics. I'm simply saying the combination of the ADuM isolator on the CM6631A converter made a very significant difference in a perceived bloom of the image over the converter alone and apparently over the older Off-Ramp 3.
The ADuM allowed the CM6631A driver (Schiit's driver package) to load without a hiccup. There is a drawback in the ADuM is limited to a throughput equivalent of 24 bit 96 kHz audio. Also, my experience includes the lossy S/PDIF part of the circuit that's almost certain to be measurably worse than using the ADuM on Schiit's well designed USB input. In other words there's a potential for your experience to be better than mine. Makes me want to get a gen 2 board.
Trying this will cost you $30 to $50 USD for the basic ADuM4160 USB isolator plus a decent little 12 VDC wall wart. You'll also need another short USB cable comparable to the proper quality cable you're using with the Schiit DAC. I take no responsibility for you trying it. As I said, I'm not completely certain it will work on the Schiit gen 2 USB board but I completely believe it should work and it may provide a very significant increase in the quality of stereo image coming from your Schiit DAC.
EDIT/UPDATE, August 21.
I've done a lot more searching on the web and everything I've seen says the ADuM and the USB-S/PDIF converter combination I'm using should not be working. I've seen at least a couple of testimonies that state the ADuM does not work with the earlier version of the C-Media chip. There is apparently no one else in the world that's tried the ADuM USB isolator with the newer version of the C-Media chip, except maybe the techs at Schiit. I bit the bullet and bought the gen 2 USB board today. I'll try it with the ADuM and update the post again later.
It's difficult to express just what an amazing upgrade these parts have had in my audiophile music server system. It's clear that the voodoo combo I mention in this post has trounced the Off-Ramp 3. If the gen 2 USB board doesn't work with the ADuM isolator and the gen 2 USB is inferior without it, it will prove the value of the voodoo combo ADuM/USB converter.
Edited by Newk Yuler - 8/21/13 at 7:36pm