What DAC's have a USB input?

Do most? Do few? Will they all in the future? I don't know. Please enlighten me. Thanks!
All USB dac's have usb inputs, they are used as a way to take sound from your computer hard drive without use of the computers soundcard. A lot of computers have very poor soundcards so people use usb dacs. Is this what you were asking about?
Sogood1 - I'm wondering if Chord, Krell, and other high-end audiophile DAC's have started to incorporate a USB input. A list of USB to optical (or coax) converters would also help. Thanks for responding.
Sorry I can't give you a list, but yes there are some high end usb dacs. There has been a few threads which listed a few of them. If you do a search of past threads you should find a few names. Hope this helps