Stereo Output Mixer with Level and Pan controls per channel. The PCB also includes two independent VCAs. These VCAs can be used on their own, or they can be wired inline with the inputs of the stereo mixer to be used as voltage control for each channel. The default BOM includes AC coupling capacitors for these VCAs, but they can be omitted and jumpered for DC coupling. When the suggested OPA2604 op amps are used, this module can drive 600 Ohm loads such as headphones.