The idea for creating a USB sound card based on a PIC came from discussions of other people creating one on the Microchip USB forum. The hardware of the card is based on all Microchip products. The software uses a modified version of the Microchip USB framework and is interrupt driven instead of the traditional polling. The device is a USB composite device as far as the hardware is concerned. The first device is an implementation of the USB Audio 1.0 interface and the other device is a custom interface based on WinUSB. The purpose of the custom interface is for programming the device serial number, upgrading the firmware, and in the future any other configuration that isn’t supported directly by USB Audio 1.0. The sound card runs at a sample rate of 48KHz, 32KHz or 24KHz selectable by the OS with 12 bits per sample. The quality approaches commercial grade as the sample rate is higher then CDs.
A Microchip PIC based USB sound card – [Link]