The dbx 166xs is a professional dual-channel compressor, limiter, and gate engineered to bring polished, professional sound to live sound reinforcement, studio recording, broadcast, and post-production applications. Housed in a rugged 1U rackmount chassis, this device builds upon dbx's legendary legacy as the inventor of the modern audio compressor, incorporating decades of refinement into a single comprehensive dynamics processor. The 166xs excels at smoothing uneven levels, adding sustain to guitars, fattening drums, and bringing vocals forward in a mix with exceptional clarity and musicality. To protect expensive downstream equipment, the PeakStop limiter provides an absolute ceiling for peak excursions and large transients that could otherwise damage amplifiers or loudspeaker drivers.

Each independent channel features comprehensive control over threshold (-40 dBu to +20 dBu), ratio (variable from 1:1 to infinity:1), output gain (-20 to +20 dB), and threshold characteristic selectable between dbx's patented OverEasy soft-knee compression or classic hard-knee based on the original dbx 160 characteristics. The AutoDynamic attack and release controls, found exclusively on dbx compressors, automatically adapt to program material timing, putting great sound within easy reach while manual control remains available for engineers who prefer to dial in their own settings. Attack times are program-dependent and range from 3ms to 340ms for 15dB of gain reduction, while release times vary from an aggressive 200dB per second to a gentle 3dB per second depending on signal characteristics.

The expander/gate section incorporates advanced timing algorithms that ensure the smoothest release characteristics, with a threshold range from OFF to +15 dBu, a fixed 10:1 ratio, attack time under 500 microseconds, and adjustable release from 30ms to 3 seconds. An adjustable PeakStop limiter with threshold from 0 dBu to +20 dBu provides an additional layer of protection. The sidechain insert allows external processing such as equalization or filtering to be inserted into the VCA control loop, enabling frequency-selective compression. When channels are stereo linked via front-panel switch, True RMS Power Summing detection ensures coherent imaging while maintaining the musical character of the compression. Comprehensive metering includes an 8-segment gain reduction display, three-LED compressor threshold indicator, and dedicated LED for gate status, all easily readable under any lighting condition with backlit switches. The 166xs operates at either +4 dBu or -10 dBV nominal levels via rear-panel switching, accepts balanced XLR and 1/4-inch TRS connections, and draws just 15 watts from an internal universal power supply.