This electronic circuit is an high quality preamplifier with built-in DAC from SPDIF or USB for my power amplifier Leachamp. I had available circuit PCM2902. I tried to design DAC from USB with this circuit on one-sided PCB and I was succesful.
Schematics is from datasheet of PCM2902. Circuit includes DAC and ADC, SPDIF output and input and HID part with 3 buttons for MUTE, VOL+ and VOL-. I used only DAC part. Other parts are not used. For high quality playback is needed to use external low-drop voltage stabiliser for DAC part. I used LP2951CM which was available at local store. Output voltage is set to about 3.7V with two resistors. Circuit board is designed regarding to good ground placement and separating of analog and digital ground. These ground are connected in one point at USB connector.
Source: http://www.pavouk.org/hw/usbdac/en_index.html
