V2164D Quad VCA IC by Coolaudio.
The V2164 contains four independent voltage controlled amplifiers (VCAs) in a single package. High performance (100 dB dynamic range, 0.02% THD) is provided at a very low-cost-per-VCA, resulting in excellent value for cost sensitive gain control applications. Each VCA offers current input and output for maximum design flexibility, and a ground referenced -33 mV/dB control port. The V2164 is available for many applications such as Automatic Volume Controls, Audio Mixers, Compressor / Limiters / Compandors, Noise Reduction Systems, Automatic Gain Controls, Voltage Controlled Filters, and Effects Processors.