Red Wine Audio USB Select.
The only one I know if that has yet to be mentioned is the Headroom Micro Dac
There are also devices that simply convert the USB signal to streaming digital which, in turn, can be fed to a DAC of your choice by means of a more conventional cable (S/PDIF, Toslink (Optical), Balanced). The Waveterminal U24 can act as one of those. The M-Audio Transit is a simple, inexpensive one. M-Audio makes other devices that can do the same and have more bells and whistles. The Airport Express can act as a wired or wireless version and also has a cheapy DAC in it which may be bypassed. There are others as well, but those are what comes to mind.
PS I'm not pushing or dissing any of these devices, but I can tell you I'm happy with my Waveterminal U24.
This is a great list. I am wondering though, some/all of these boxes perform D/A from a computer's USB port. Are any of these better than others for pure switching capabilities? What I mean by this is: if you are going to only use one of these devices with another DAC anyway, will any of these do a better job than the others of converting the signal from the computer's USB into a coaxial or optical signal to be sent to a DAC?
For example, I am using a Waveterminal U24 to get the signal out of the USB port of my laptop. From the Wavterminal I am using a coaxial cable into my DAC. Is one of these units better than others for just this purpose?
(Also to add to the list we have going, I was just at the CEC website and their DAC 53 has USB input.)
Interesting new offering on EBay. Looks like a 24-192KHZ USB DAC with battery option - need to research the chip info.
I myself have a Waveterminal U24 which has been truly amazing through my CAL Alpha (18 bit) for redbook. I'm sitting tight until the techonolgy matures. Meanwhile I'm enjoying music and concentrating more on ripping CD's/storing files and keeping tabs on new devices.