Digitally Controlled 6 Channel Audio Attenuator

The RDL RU-VCA6A is a digitally controlled six-channel audio attenuator for local or remote level adjustment. It provides a 96 dB attenuation range in precise 0.5 dB steps, with noiseless zero-crossing adjustment and close level tracking across all six channels. Balanced or unbalanced line-level sources and destinations are supported, while selectable control modes accommodate front-panel operation, external controls, remote potentiometers, and 0 to 10 Vdc control signals.

Ideal Use Cases

This model is suited to six-channel and surround audio systems that require coordinated attenuation across multiple channels. It is also appropriate when audio levels must be adjusted from one or more remote locations, when repeatable half-decibel changes are needed, or when several attenuator modules must operate under common control. Selectable momentary and voltage-control modes allow the RU-VCA6A to work with pushbuttons, rotary-encoder pulses, a 10 kΩ linear-taper potentiometer, or an external 0 to 10 Vdc source.

Why Choose This Model

The RU-VCA6A combines a wide control range with detailed level resolution. Its 96 dB range is divided into 0.5 dB steps, and each adjustment occurs through noiseless zero-crossing steps. Six channels track precisely as the level changes. The unit has six greater-than-10 kΩ balanced bridging inputs that may also be used unbalanced, plus six 150 Ω balanced outputs that may be connected unbalanced. Its front panel provides eight LEDs for relative level, a green MAX indicator, and a red MIN indicator.

Selectable power-up behavior returns the audio either to a stored preset or to the last level used. This makes startup operation adaptable without requiring the same default behavior in every installation.

Installation and Integration

In MOM momentary mode, audio level can be controlled from the front-panel pushbuttons or through remote up-and-down terminals. Holding a button initiates automatic ramping. A control pulse shorter than 0.5 second changes the level by one step. The up and down ramp times are individually adjustable from the front panel, with a 0.5-second delay followed by a selectable ramp duration from 3 to 10 seconds.

A remote GO TO PRESET button can return the audio to a stored level. The preset is established by selecting the desired level with the up and down controls and then holding the front-panel PRESET button for three seconds. Multiple remote control locations are possible in MOM mode, and external pulses may be positive-polarity or pulled to ground through an open-collector control.

In 0 to 10 Vdc mode, level is controlled by a remote 10 kΩ linear-taper potentiometer or a 0 to 10 Vdc signal. The preset function is disabled in this mode, and a single remote location is possible when using the potentiometer. The unit requires ground-referenced 24 Vdc at 200 mA. Recommended power supplies, not included, are the PS-24AS for the USA and PS-24AX for international use.

Performance Highlights

Frequency response extends from 10 Hz to 50 kHz within ±0.5 dB. THD+N is less than 0.005% from 20 Hz to 20 kHz, while headroom is greater than 18 dB above +4 dBu. Residual noise is below -90 dB when referred to +4 dBu at unity gain, and common-mode rejection is greater than 65 dB from 50 to 150 Hz. These published measurements are paired with precise channel tracking and half-decibel control resolution.

What Makes It Different

Control expansion is available through the EXTERNAL CONTROL DATA jacks. One RU-VCA6A can operate as the MASTER and control one or more additional RU-VCA2A or RU-VCA6A modules configured as SLAVES. This data-bus capability extends coordinated adjustment beyond a single six-channel module.

The ground-referenced 0 to 10 Vdc RAMP output drives the level display on compatible RDL remote controls; it is not intended to drive additional VCA 0 to 10 V inputs. A separate ground-referenced EQ RAMP output has a DC taper intended only for the RDL ST-LEQ1 Loudness EQ. Together with selectable local and remote control methods, these dedicated outputs support integration with specific RDL control and loudness-equalization functions.

Final Assessment

The RU-VCA6A provides six-channel attenuation with a 96 dB range, 0.5 dB resolution, zero-crossing adjustment, and balanced or unbalanced line connections. Its selectable control modes, adjustable ramping, preset or last-level startup options, dedicated control outputs, and master/slave expansion make it a flexible choice for systems that need precise, coordinated local or remote audio-level control.