1x4 Audio Distribution Amplifier

The RDL RU-MLD4 is a 1×4 audio distribution amplifier built around one input and four outputs. It accepts microphone- or line-level operation and provides front-panel XLR input and output jacks together with detachable input and output terminal blocks on the rear. Rear-panel switching selects mic or line input operation, while the microphone path adds selectable gain and phantom power. A front-panel gain trim provides direct level adjustment, and each output can be individually selected for mic or line level.

Ideal Use Cases

The RU-MLD4 is intended for systems that need to distribute a single audio source to as many as four destinations. It fits signal paths in which the source may be microphone level or line level and the receiving devices do not all require the same output level. Front XLR connections provide input and output access from the face of the unit, while rear detachable terminal blocks accommodate fixed wiring layouts. These connection and level options are useful when one installation must support different mic and line interface requirements.

Why Choose This Model

The main reason to choose this model is its control at both sides of the distribution path. The input is not locked to one signal class: a rear selector sets MIC or LINE operation, with low- and high-gain microphone ranges listed in the specifications. Phantom power is also switch-selectable for the microphone input. On the output side, each of the four feeds has its own mic or line selection. This allows the RU-MLD4 to be configured around the connected equipment without requiring all four destinations to accept one common output level.

Installation and Integration

Installation begins by connecting the source to either the front-panel XLR input or the rear detachable terminal block and selecting MIC or LINE on the rear panel. For microphone operation, choose the available mic gain and phantom settings for the connected source, then use the front-panel gain trim for level adjustment. Connect as many as four destination paths using the corresponding front XLR outputs or rear terminal blocks, setting each output to MIC or LINE as required.

The unit requires ground-referenced 24 Vdc power at 90 mA. The recommended supply is the PS-24AS for the USA or the PS-24AX for international use; the power supply is not included. The specified ambient operating range is 0 degrees C to 55 degrees C. Package dimensions are 6 x 6 x 2.625 inches, with a shipping weight of 1.48 pounds.

Performance Highlights

At line level, specified THD+N is less than 0.005 percent; at microphone level, it is less than 0.1 percent. Common-mode rejection ratio is greater than 50 dB in line mode and greater than 60 dB in microphone mode. The amplifier provides greater than 20 dB of headroom above a +4 dBu line output, and its outputs have a balanced impedance of 150 ohms.

For a +4 dBu output, the listed microphone input range is 48 dBu to -3 dBu in LO GAIN mode and -65 dBu to -20 dBu in HI GAIN mode. The listed line input range is 15 dBu to +28 dBu. These selectable operating ranges complement the front-panel trim and allow the input section to be configured for the selected source type.

What Makes It Different

The defining feature of the RU-MLD4 is the combination of front-panel XLR connectivity, rear detachable terminal blocks, and individual mic or line selection for all four outputs. Many of its configuration choices are accessible without changing the basic distribution arrangement: the source remains a single input, while output levels can be assigned separately for connected destinations. Switch-selectable mic gain and phantom power add further input-side control, and the front gain trim keeps the primary adjustment readily accessible.

Final Assessment

The RU-MLD4 is a focused distribution solution for routing one microphone- or line-level source to four independently selectable mic or line outputs. Its dual connection formats support front-access and rear-wired integration, while the published distortion, rejection, impedance, and headroom specifications provide concrete performance guidance. It is best considered when flexible signal-level selection and four-way distribution are required, with the external 24 Vdc power supply planned separately.