I just finished building my pupDAC and it can output sound through Windows, but there's a big problem. I've already set the pupDAC as the default device in Windows settings, but somehow the volume control on my taskbar does absolutely nothing to control the volume level. Pulling the slider all the way up or down makes no difference to the volume (all really loud), all while the grey bar keeps moving up and down (the green bar is not there since the volume is set to 0, but it's still extremely loud).
My pupDAC is linked to my headphones (I don't have an amp yet), so there's no way to control the volume level.
What can I do?
Try Left-clicking on the icon in the taskbar. Select "Playback devices" from the pop-up context menu. Select the pupDAC from the collection of playback devices in the pop-up window. If you made the pupDAC the default device, it will have a big green check-mark beside it. When selected, Right-click and select "Properties" from the pop-up context menu. Select the "Levels" tab from the pop-up window. Adjust it there and see if makes a difference.
Honestly, there is a bug (sorry - different "Windows Feature") in Windows 7 that manifests itself with the PCM2704/5/6/7. It causes a conflict with the taskbar volume control when you make the device the default. Texas Instruments has come out with the PCM2707C to combat this, but it is not supplied with pupDAC kits by default.
I've never had this problem with Foobar2000, which seems to be the standard for most folks. It allows you to specify the source and there's never any issue. I would search for other media players that allow you to do this, assuming you're not happy with Foobar2000. The problem comes up when selecting a USB device as default in Windows 7 with a PCM2704/5/6/7.
Remember though - if you are adjusting volume through the operating system in any configuration with an off-board DAC, the USB is re-interpolated causing bits to be lost. It's absolutely the wrong thing to do. Pure sources like the pupDAC are intended to be used with an amp. That removes the issue in every single case and ensures the best quality signal from the source.