In the simplest terms, the SansAmp RPM is Tech 21's SansAmp Acoustic DI pedal in a rackmount format adapted into an expanded multi-instrument tool. This instrument pre-amp features the same parametric equalization and SansAmp processing with the addition of a Drive control. It makes an excellent partner for Tech 21's SansAmp RBI pre-amp for bass or SansAmp PSA-1 programmable pre-amp for guitar. Active Bass and Treble tone controls cut or boost 12dB. Sweepable semi-parametric EQ controls, Mid Shift & Mid, range from 170Hz to 3.0 kHz, 16dB, respectively. Blend mixes the amount of SansAmp circuitry with the direct instrument signal. There's an individual level control for the XLR output to optimize an amp's output relative to the PA system. Engineered for both studio and live applications, SansAmp RPM is designed to go direct into the mixing console of a recorder or P.A. system. It can also be used with conventional acoustic or electric guitar amps to enhance and expand their capabilities.Other features of the rackmount include an effects loop with a Mix 50/50 switch for series or parellel operation, rear 1/4" input and XLR output with selectable levels, buffered uneffected XLR output to run a dry signal to a separate channel, footswitch input to engage unit, and footswitch output to chain and toggle between a SansAmp RBI or SansAmp PSA-1.