Mic Level Distribution Amplifier-1x3

The RDL STM-DA3 is a compact 1×3 microphone-level distribution amplifier designed to feed one microphone signal to three microphone inputs. It combines balanced audio connections, electrical and audio isolation, adjustable gain, low-noise and low-distortion performance, and a built-in dual-LED VU meter. Its STICK-ON compactness makes it suitable for systems that need straightforward microphone signal distribution in a small module.

Ideal Use Cases

The STM-DA3 is intended for installations where a single microphone must serve three separate microphone inputs. It provides one balanced 1.2 kΩ input and three balanced outputs, allowing the source signal to be distributed without requiring three microphones or an external level-monitoring device during setup.

Its compact format is useful when available installation space is limited. The specified studio-quality performance, electrical and audio isolation, and excellent phase response also make it appropriate when maintaining signal quality across all three destinations is important.

Why Choose This Model

This model combines microphone distribution and level adjustment in one module. The gain range spans 17 dB and is adjusted with a 25-turn trimmer. With the control fully counterclockwise, gain is -5 dB; with the control fully clockwise, gain is 12 dB. This adjustment range allows the operating level to be matched to the connected microphone inputs.

A dual-LED VU meter helps simplify setup. The green LED begins illuminating at 15 dB below the optimum level and progresses from minimum to full intensity across a 15 dB range. The adjacent red LED illuminates when the signal exceeds the optimum operating level.

Installation and Integration

The STM-DA3 uses a balanced 1.2 kΩ input and three balanced 150 Ω outputs. The gain control and adjacent dual-LED meter allow the installer to set and monitor the operating level directly at the module without external test equipment. The module requires ground-referenced 24 Vdc power at 40 mA.

The recommended power supply is the PS-24AS for the USA or the PS-24AX for international use. The recommended power supply is not included. The specified ambient operating range is 0° C to 55° C, providing a defined temperature range for installation planning.

Performance Highlights

Frequency response is specified from 30 Hz to 20 kHz within ±0.2 dB. THD+N is below 0.1%, and IMD is also below 0.1%. The stated noise specification is below 80 dB relative to a -50 dBu output and -50 dBu input. Headroom is greater than 20 dB at a -50 dBu output and -45 dBu input.

Common-mode rejection is greater than 60 dB from 100 Hz to 5 kHz. Output isolation exceeds 135 dB for balanced audio and 150 dB for common mode. Together with the stated low-distortion performance and excellent phase response, these specifications define the STM-DA3 as a focused microphone-distribution component rather than a general-purpose signal splitter.

What Makes It Different

The distinguishing combination is one-to-three microphone distribution, electrical and audio isolation, a precision 25-turn gain trimmer, and level monitoring built directly into a compact STICK-ON module. The progressive green indication provides a visible reference as the signal approaches the optimum level, while the red indication identifies operation above that level.

This onboard monitoring reduces the equipment needed for initial level adjustment and continues to provide operating-level visibility at the module. The three balanced outputs and stated output-isolation figures address applications where one microphone signal must be delivered to multiple microphone inputs.

Final Assessment

The RDL STM-DA3 offers a clearly defined solution for feeding one microphone to three microphone inputs. Its balanced input and outputs, adjustable -5 dB to 12 dB gain, 30 Hz to 20 kHz response, low stated distortion, high output isolation, and dual-LED VU meter provide the core functions needed for compact microphone-level signal distribution. For installations requiring three microphone feeds from one source, it combines level control, monitoring, isolation, and compactness in a single module.