The RDL SF-PA50A is a 50-watt audio power amplifier that converts one analog input to a 70 V or 100 V constant voltage amplified output. An analog audio source may be connected to either the mono balanced terminal block input or to the unbalanced Mini-Jack, which sums the left and right channels to mono. Amplifier gain is set by the installer using a rear-panel single-turn potentiometer with an associated dual-LED VU meter calibrated to 20 dB below maximum power output. The RDL SF-PA50A is equipped with an internal VCA for setting the amplifier output level. 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 ensures long term noise-free level adjustment. Designed for both thermal and output short-circuit protection; included is an external 24Vdc power supply and all-metal enclosure. Engineered and manufactured in the USA.