The RQD 6400 Twin Stereo Compressor/Limiter is two independent stereo compressor/limiters. The rear panel features four female XLR connectors for audio input (Channel 1 left, Channel 1 right, Channel 2 left and Channel 2 right) and four male XLR connectors for audio output (Channel 1 left, Channel 1 right, Channel 2 left and Channel 2 right).

The compressor has a variable ratio from 1.5:1 to 10:1 and a adjustable threshold. Attack time is selected by a switch as either fast or normal. Controls for both the compressor and the limiter sections are identical for both stereo channels of the RQD 6400. The only other controls are the power switch located on the front panel and the link button that joins the two stereo compressor and limiter sidechains together to form a quad unit.The ability to perform extremely high-quality compression and limiting in quad makes the RQD 6400 a powerful tool for both film and television work.