Studio Quality Mic Preamp w/phantom-3 Line Outputs

The RDL STM-LDA3 is a compact STICK-ON microphone preamplifier built around studio-quality microphone preamplification and three distributed line-level outputs. Its balanced 1.2 kΩ input feeds three balanced 150 Ω outputs operating at +4 dBu, while a 25-turn gain adjustment provides a 40 to 60 dB range. Selectable filtered phantom voltage supports installations that require phantom power, and the module combines low-noise, low-distortion operation with local dual-LED VU metering.

Ideal Use Cases

The STM-LDA3 is well matched to systems that need one microphone signal delivered to three balanced line-level destinations. Its compact STICK-ON format suits space-conscious integration, and its on-module metering is useful when installers need to establish or observe operating level at the equipment. The combination of adjustable microphone gain, phantom-voltage selection, and distributed +4 dBu outputs makes it relevant where a microphone source must be conditioned and routed from one compact module.

Why Choose This Model

Choose this model when the required signal path begins with a balanced microphone input and ends at as many as three balanced line-level outputs. The gain range reaches 60 dB but can be set as low as 40 dB, allowing the preamplifier to be matched to the source with fine 25-turn adjustment. RDL’s metering approach also provides immediate level information at the module: green indicates the signal’s progression toward +4 dBu, while red identifies operation above +4 dBu.

Installation and Integration

Installation centers on the balanced 1.2 kΩ input, the three balanced +4 dBu outputs, and a ground-referenced 24 Vdc power connection rated at 40 mA. The recommended power supplies are the PS-24AS for the USA and PS-24AX for international use; the power supply is not included. After connecting the signal paths, set the 40-to-60 dB gain and select filtered phantom voltage as required. The adjacent dual-LED meter lets the operating level be set without external test equipment. The module is specified for ambient operation from 0° C to 55° C.

Performance Highlights

Frequency response is specified at 30 Hz to 20 kHz within ±0.2 dB. Both THD+N and IMD are below 0.1%. Wideband noise is below -70 dB relative to +4 dBu at 60 dB gain and below -80 dB relative to +4 dBu at 50 dB gain. Equivalent input noise is below -130 dB, expressed as gain plus residual noise below +4 dBu. The unit provides more than 20 dB of headroom above +4 dBu and CMRR greater than 60 dB from 100 Hz to 5 kHz. Together, these figures define the model’s low-noise, low-distortion performance and operating margin without extending beyond the published specifications.

What Makes It Different

What distinguishes the STM-LDA3 is the pairing of three distributed outputs with RDL’s dual-LED VU display in the STICK-ON form factor. The green LED first illuminates at 15 dB below a +4 dBu output, then increases from minimum to full intensity as the output reaches +4 dBu. The adjacent red LED illuminates once the operating level exceeds +4 dBu. This gives the installer a direct visual reference for adjustment and allows operating levels to be monitored at the module, without requiring separate test equipment for setup.

Final Assessment

The STM-LDA3 is a focused solution for studio-quality microphone preamplification, fine gain adjustment, selectable filtered phantom voltage, and delivery to three balanced +4 dBu outputs. Its measured bandwidth, distortion, noise, headroom, and common-mode rejection specifications are reinforced by a practical local metering system. For installations that call for this exact one-input, three-output signal path in a compact RDL module, it offers a clearly defined set of audio and setup capabilities.