4 Channel Microphone/Line Mixer w/ Phantom Power

The RDL RU-MX4T is a professional four-channel microphone/line mixer designed for flexible source matching, adjustable gain, visible metering, and multiple output levels. Its four balanced 2 kΩ microphone inputs provide individually switchable 24 V phantom power, while four 2 kΩ unbalanced line inputs accommodate line-level sources. An integrated compressor/limiter provides mix processing, and the 18 indicators display input levels, processing activity, power status, and overall audio mix level.

Ideal Use Cases

This model is suited to audio systems that need to combine as many as four microphone or line sources. It directly supports configurations that include phantom-powered microphones, unbalanced line-level devices, or a combination of source types. The two output formats also make the mixer practical when one system requires a balanced +4 dBu signal and another connection requires an unbalanced −10 dBV signal. Because the balanced output can be switched to −45 dBu microphone level, the RU-MX4T can also connect with downstream equipment expecting a mic-level feed.

Why Choose This Model

The RU-MX4T provides separate gain ranges for its microphone and line inputs. Microphone gain adjusts from off to 62 dB with phantom power off or with phantom-on high gain, and from off to 46 dB in the phantom-on low-gain mode. Line gain adjusts from off to 27 dB. A separate output attenuator covers 0 dB to infinity. This range of control allows input levels and the outgoing mix to be set independently. The integrated compressor/limiter adds level management without requiring that function to be supplied by a separate device.

Installation and Integration

The mixer requires ground-referenced 24 Vdc power at 150 mA. The recommended power 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° C to 50° C. For input planning, each microphone input presents a balanced 2 kΩ connection with switchable 24 V phantom power compliant with IEC 61938: 2013, while each line input is unbalanced at 2 kΩ. Output connections include a 150 Ω balanced output operating at +4 dBu, switchable to −45 dBu mic level, and a −10 dBV unbalanced output. The product ships in a 6 x 6 x 2.625-inch cardboard package with a listed shipping weight of 1.845 pounds.

Performance Highlights

The specified microphone frequency response is 80 Hz to 30 kHz within ±1.5 dB. Published THD+N is less than 0.1% for microphone signals from 80 Hz to 20 kHz and less than 0.02% for line signals. The line-input specification identifies −10 dBV as the nominal level. Monitoring is handled by dual-LED VU indication for each input and an LED audio mix meter. The mix meter provides VU points at −20, −10, −6, −2, 0, and +3 dB, with 0 dB corresponding to a +4 dBu output. Peak readings are provided at +8 and +12 dB. Dedicated LEDs indicate compressor/limiter activity and power status.

What Makes It Different

The defining feature set combines per-microphone-input phantom switching, microphone and line gain adjustment, integrated compression/limiting, and detailed visual monitoring in one four-channel mixer. Each source receives its own dual-LED VU indication instead of relying only on the final mix meter. The output section is similarly adaptable: it provides balanced and unbalanced feeds, while the balanced output can change between +4 dBu line level and −45 dBu microphone level. These options allow the same mixer to address several signal-level requirements using its built-in controls and outputs.

Final Assessment

The RDL RU-MX4T is a focused choice for four-channel microphone and line mixing where phantom power, adjustable gain, integrated compressor/limiter processing, and visible level monitoring are required. Its balanced +4 dBu output, selectable −45 dBu mic-level mode, and separate −10 dBV unbalanced output provide clearly defined integration options. A compatible 24 Vdc power supply must be obtained separately.