The RU-PA40D is the ideal choice in many applications where a high quality, high-efficiency utility amplifier is needed to drive a pair of 4 Ω or 8 Ω speakers. It is specifically suited to amplification applications where users need to adjust the gain. Examples include projectors or monitors with fixed audio outputs used in classrooms, boardrooms or video conferencing. The RU-PA40D is ideal for foreground sound amplification in small to medium rooms or in a specific zone within a retail space. The RU-PA40D features two balanced line-level inputs on a detachable terminal block. Two unbalanced line level inputs are available on high-reliability gold plated phono (RCA) jacks. A front-panel gain control trimmer permits setting the maximum gain for each channel. The gain range accommodates the range of typical balanced and unbalanced audio signal levels. Each of the two RU-PA40D outputs will drive a 4 Ω or 8 Ω speaker or multiple speakers connected to present a 4 Ω or 8 Ω load to the amplifier. The output impedance is switch-selectable on the front panel of the module. The RU-PA40D is equipped with an internal stereo VCA for setting the output level on both amplifier channels. A detachable terminal block provides for the connection of an external 10 KΩ potentiometer or a 0 to 10 Vdc control voltage. RDL remote controls are available to provide single-turn, multi-turn (rotary encoder) or pushbutton (ramp or fixed level selection) user level control. VCA control insures long term noise-free level adjustment. Remote control is possible using audio, control or common computer network wire. A front-panel switch is provided to sum the audio inputs to mono. In the STEREO mode, the RU-PA40D independently amplifies each audio channel, left (L) and right (R). If speaker placement in the specified installation is incompatible with stereo amplification, the INPUT MODE switch may be set to SUMMED MONO. The RU-PA40D includes a stereo analog compressor/limiter for audio fidelity noticeably superior to conventional class D amplifiers with digital limiting. The input GAIN settings determine whether the limiter alone is used for clipping suppression, or if the full compressor/limiter will be used to substantially increase the average output power beyond that of a standard 40 W amplifier. A red front-panel LED flashes when the limiter is preventing output clipping. The RU-PA40D, with compression, is capable of producing average audio output levels and clarity normally expected from stereo amplifiers with a much higher output power rating. A blue POWER LED illuminates when the RU-PA40D is powered from its external 24 Vdc power supply (included). The module is equipped with both thermal and output short-circuit protection. The high-efficiency Class D output stages produce minimal heat for all levels of expected voice or music modulation.