The RU-MLD4 is a four channel audio distribution amplifier. The input and all four outputs may be connected through the front-panel XLR jacks or on the rear panel detachable terminal blocks. The input accepts either a balanced microphone or line level signal. Each of the four outputs provides either a microphone or line level signal. Both the front-panel XLR connectors and the rear-panel terminals are active at all times. The RU-MLD4 may be rack-mounted with the XLR jacks facing forward, or may be reverse-mounted using the RDL RU-FP1 Filler Panel/Reverse Mount Kit.

The audio input is equipped with a rear-panel switch to select between MIC and LINE level. Two additional switches allow setting the MIC input for LO or HI gain and for enabling or disabling standard 24 Vdc phantom. The two microphone gain settings allow the connection of a wide variety of dynamic and condenser microphones. Each output is provided with a separate rear-panel switch to set the associated level to either MIC or LINE. Audio outputs are isolated from each other and may be wired balanced or unbalanced. Gain trim is provided on a front-panel control. The knurled adjustment is provided with a screwdriver slot so the gain may be adjusted by hand or by screwdriver. An RDL Dual-led VU meter is provided above the gain trimmer. The meter is calibrated to indicate +4 dBu for outputs set to line level. The rear panel provides a detachable terminal block and a power input jack to connect 24 Vdc power. Each output of the RU-MLD4T is equipped with a studio-quality audio output transformer.