Agree with Durwood..
Most USB DACs have a mainstream usb chip that Windows recognizes and it will Plug&Play as a 'USB Audio Device.' There is no more software at all, no EQ, mixer, etc as it is using generic drivers from windows.
With Foobar and Winamp it will then show up in your output preferences. You can send the music via Kernel stream or DirectSound output to the USB DAC direct from Winamp/Foobar. Your primary sound card is still there and you can use it for other things if you want/need and use the DAC for music only... Of cours you could select the DAC as yor primary sound card also, but the music will then be sent through the Windows Audio stack and be resampled.
Most of these are designed as high end Headphone amps and Different units have different designs, so they vary in output voltage, DAC chips, etc.
I will tell you that i use 'The Bloat' from HippoHifi and LOVE it. I am not using it in my car, as it has only 1 pair of stereo output at 4V, but i do use it in my home rig and also as a Headphone amp. It is amazing how much better it sounds than a off the shelf or onboard soundcard..
Laters...
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