The SP-20A is a stereo power amplifier housed in a half-rack chassis that delivers 20 watt per channel into either 4 ohms or 8 ohms. It is ideal for recording studio applications, where it can be used to drive small reference speakers, or as a headphone driver for the HR-2 headphone remote stations, while doubling as the tape playback amplifier in the tracking room. The SP-20A may be operated in any of three modes as selected by a rear-panel switch: normal stereo, two channel mono, or single channel (bridged) mono. The latter mode allows a power output of 40 watts provided the load is 8 or more ohms. Output is available through either of two connectors. Standard banana jack binding posts for speakers, or through a male XLR connector. The latter allows the unit to become the headphone driver. The amplifier has an input level control on the left side of the front panel. A pair of yellow LEDs, one for each channel -- light up whenever signal is present. Another pair of red LEDs warns of any overload condition present in either channel. The SP-20A is fully protected against thermal overload, and it can withstand a short circuit on any or all outputs for an indefinite time without damage.Stereo power amplifier ideal for small speakers or headphone system Toroidal transformer provides for ultra-quiet performance Overload and signal-present LEDs for each channel Bridged mono, two channel mono and stereo operation Speaker on-off switch Front panel headphone jack with volume control Convection cooling system dissipates heat through the heat sinks and chassis for optimal cooling and maintenance-free operation