4 Channel Audio Meter-Average/Peak/Hold

Ideal Use Cases

The RDL RU-SM16D is designed for applications where four audio feeds need to be viewed at the same time. It can be configured as four mono meters or two stereo meters, supporting multi-channel monitoring, comparison between stereo pairs, and level checks across separate signal paths. Its four inputs accommodate line-level audio, amplified speaker-level signals, and 25, 70, or 100 V audio. This input support covers balanced or unbalanced feeds, constant-voltage systems, and low-impedance 4 Ohm or 8 Ohm amplifier outputs. Each channel presents level information on its own digital 16-LED string display.

Why Choose This Model

Channel-by-channel control is central to the RU-SM16D. Each channel can be independently switched between peak and average metering, allowing different signal paths to be evaluated with the response best suited to each feed. Calibration can be switched between fixed and variable operation, and individual channel calibration controls support separate adjustment of all four meters. Peak-hold indication at +10, +14, and +18 dB makes elevated peaks easier to identify after they occur. These capabilities combine multi-channel visibility, selectable response behavior, and flexible calibration within one precision audio level meter.

Installation and Integration

The RU-SM16D provides four inputs for line-level or amplified speaker-level signals. Input impedance is greater than 40 kΩ and supports balanced or unbalanced connections. Fixed 0 dB calibration settings accommodate +4 dBu, 25 V, 70 V, or 100 V input references. The published variable ranges are 24 dBu to +12 dBu with the +4 switch settings, 2 V to 90 V with the 25 V settings, 4 V to 90 V with the 70 V settings, and 5 V to 100 V with the 100 V settings. Voltage settings apply to constant-voltage or low-impedance amplifier outputs. Power requirements are ground-referenced 24 Vdc at 450 mA. The recommended supplies are the PS-24AS for the USA and PS-24AX for international use.

Performance Highlights

Metering frequency response extends from 20 Hz to 20 kHz. Each channel has 16 LED positions labeled SIG, -20, -15, -12, -9, -6, -3, -2, -1, 0, +1.5, +3, +6, +10, +14, and +18. The +10, +14, and +18 positions operate as peak-hold indicators only. In peak mode, rise time is 50 us from 10% to 90% and 60 us from 0% to 100%. Average-mode rise times are 130 ms and 300 ms respectively, with the 0% to 100% value identified as a VU characteristic. Peak-mode fall times are 65 ms from 90% to 10% and 100 ms from 100% to 0%. Corresponding average-mode fall times are 185 ms and 300 ms, with the latter identified as a VU characteristic.

What Makes It Different

The RU-SM16D combines four independent meter channels with support for both low-level and amplified audio sources. A single unit can display four mono feeds or two stereo pairs without limiting every channel to the same metering response. Independent peak or average selection, individual calibration controls, fixed or variable calibration, and dedicated peak-hold positions provide several ways to adapt the display to the connected signals. Its compatibility with line, speaker, 25 V, 70 V, and 100 V inputs further distinguishes it from meters intended only for conventional line-level monitoring.

Final Assessment

The RDL RU-SM16D provides precise four-channel audio level metering with clear 16-LED displays, selectable peak or average response, and peak-hold indication at three elevated levels. Its flexible input and calibration options support line-level feeds, amplified speaker signals, and distributed-audio voltages. For systems requiring simultaneous monitoring of four mono channels or two stereo pairs, it offers detailed level indication and individually configurable channel behavior.