The STAC9750/9751 is a standard 2-channel stereo CODEC. With IDT's headphone drive capability, headphones can be driven with no external amplifier. The STAC9750/9751 may be used as a secondary CODEC, with the STAC9700/21/44/56/08/84/66 as the primary, in a multiple CODEC configuration conforming to the AC'97 Rev. 2.2 specification. This configuration can provide the true six-channel, AC-3 playback required for DVD applications. The STAC9750/9751 communicates via the five-wire AC-Link to any digital component of AC'97, providing flexibility in the audio system design. The STAC9750/9751 supports General Purpose Input/Output (GPIO), as well as SPDIF output. These digital I/O options provide for a number of advanced architectural implementations, with volume controls and digital mixing capabilities built directly into the CODEC.