I've had good luck using one similar to this: http://www.ebay.com/itm/MUSE-AUDIO-X5-MINI-HIFI-USB-DAC-PCM2704-SOUND-CARD-BOARD-Silver-/130907884661?pt=US_Home_

I've had good luck using one similar to this: http://www.ebay.com/itm/MUSE-AUDIO-X5-MINI-HIFI-USB-DAC-PCM2704-SOUND-CARD-BOARD-Silver-/130907884661?pt=US_Home_Audio_Amplifiers_Preamps&hash=item1e7ab7cc75 http://www.ebay.com/itm/MUSE-AUDIO-X5-MINI-HIFI-USB-DAC-PCM2... It's no frills, but the noise floor seems pretty low and it eliminates any popping sounds.