Wyred4Sound Dac-2 vs Preamp and separate DAC

For my ears, less grainy and more detailed presentation regardless of the volume.

I am using W4S DAC-2 via async USB directly into W4S-ST 500 with excellent results.
DAC-2 doesn't have a "preamp section per se". It's the usual analog section following the Sabre DAC chip.
Volume control is performed in the digital domain, before the final analog section.
Operating internally at 32 bits, the volume control doesn't lose bits of resolution even at very low volumes.
On top of this, DAC-2 is featuring slightly better components than DAC-1, besides asyc USB, volume control and HT bypass (for those so inclined to use it that way).
My advice is go DAC-2 and skip the pre, if if don't have any other sources.

I am using the S/PDIF output from a M-Audio Audiophile 192 sound card. Works great.

@ranperry: you really should try the USB async directly into the dac2. Youre missing out on the best sounding part of the unit (IMHO). I tried exacty what you have and found the m audio spdif nowhere near as good sounding as sending the usb direct to the dac2 using kernel streaming with jriver mc.

I can't. Wyred4Sound does not provide their proprietary drivers for Linux. Also, I prefer using Linux as I get Bit Perfect sound, bypassing the OSs mixer altogether. USB audio is not mature yet (this is from a hardware engineer perspective). Once DAC manufactures will start using the standard audio protocol in USB 2 and USB 3 I may give it a try. The problem is that Microsoft does not have native hi res support and Apple's own implementation is lacking. Maybe in a few years....