Twenty-two years of progressive research into loudness perception resulted in a limiter/compressor unlike any other. The 8900 Dynamic Range Controller was intrinsically developed to react to loudness (rather than voltage) like our ears do. The 8900’s psycho-acoustic approach uses multiple true-RMS detectors, remarkably accurate log converters, and fast peak detectors to respond intelligently to real signal energy, not just electrical level. This innovative design employs unique controls like Crest Factor, Timing, and Release Hysteresis to precisely control the dynamic features of musical performances; one would ordinarily change out the entire unit to gain this flexibility. Familiar features such as Stereo Link, Soft/Hard Knee, Ratio, Output Level, as well as the comprehensive 40-segment tricolor Gain/Loss metering have been carefully optimized for flexible, creative control over a wide dynamic range with a noticeable lack of audible artifacts. A Side Chain Input permits external frequency shaping to be introduced into the detection circuitry. The entire audio path is all-discrete, including the custom-built VCA, for unsurpassed transparency and low-level resolution. The 8900 is a 2U, two-channel unit which requires one 9015 power supply.