The PCM2904/2906 is Texas Instruments single-chip USB stereo audio codec with USB-compliant full-speed protocol controller and S/PDIF (PCM2906 only). The USB protocol controller works with no software code, but the USB descriptors can be modified in some areas (for example, vendor ID/product ID). The PCM2904/2906 employs SpAct™ architecture, TI's unique system that recovers the audio clock from USB packet data. On-chip analog PLLs with SpAct enable playback and record with low clock jitter and with independent playback and record sampling rates.