QSC PLX1804 Lightweight Power Amplifier Cooling design exhausts hot air out the front, keeping the rack cool Flow-through heat sinks require no filters that could become clogged Front panel LED power, clip, -10 dB, and signal present indicators for system monitoring and troubleshooting Speak on NL-4 output connectors provide a positive-locking speaker connection. Ch. 1 output uses all - 4 wires for single-cable connection to bi-amplified speakers 21-position front-panel gain controls for precise, repeatable amplifier adjustment