RDL STVCA3 Quick Start Guide

STICK-ON® SERIES

Model ST-VCA3

Voltage Controlled Amplifier

 Audio Level Control from a DC Voltage
 Audio Level Remote Control
 Two Wire with Shield or Three Wire Control
 VCA with Microphone or Line Level Input
 VCA with Line Level Output
 VCA with LED Metering of Operating Level

The ST-VCA3 is a voltage controlled preamplifier in the convenient line of
STICK-ON products, featuring the superior engineering and components
common to RDL products. The ST-VCA3 may be rack or surface
mounted with optional STICK-ON series accessories. The ST-VCA3
gives you the advantages of audio level remote control with the added
convenience of STICK-ONs!

The ST-VCA3 is a high performance voltage controlled amplifier with two inputs and one output. The line input
is designed to accept an input signal with operating levels between -20 dBV and +4 dBu. The microphone input
accepts low or high impedance microphones with output levels from –60 to –44 dBu. Only one of the inputs
may be used at a time. A multi-turn trimmer is provided for setting the correct input gain according to the
dual-LED VU meter located directly in front of the gain control. The intended output level is +4 dBu for 10 Vdc

at the CTRL input terminal. The green metering LED begins illuminating at 15 dB below +4 dBu. The green

LED progresses to full intensity at +4 dBu. The adjacent red LED illuminates at +4 dBu.

Terminals are provided for connection of an external ramp generator (0 to 10 Vdc) or a linear taper 10 kΩ
potentiometer remote control. The RDL RLC10K is most commonly used. Three terminals are provided for
external control; a single-pair shielded audio cable is recommended. If a remote volume control with a mute
button is preferred, an RDL RLC10KM may be connected directly to the ST-VCA3. The regulated +10 Vdc

control OUT voltage provides sufficient current to power an RLC10KM. The CTRL terminal does not load the

external control voltage, therefore a single 10 kΩ control may control multiple ST-VCA3s simultaneously. The

LEVEL LED varies in intensity corresponding to the VCA control voltage. This provides a relative indication at

the module of the level setting on the remote control.

The ST-VCA3 is used in applications requiring smooth audio level control from a remote control panel,
potentiometer or dc voltage (0 to 10 V). Installation in series with the audio input of a power amplifier allows
remote control of that amplifier’s level. For installations where it is preferred to keep the audio localized in a
rack or common equipment location, audio level control may be extended outside the rack using an ST-VCA3.
Many installations benefit from avoiding long-term wear from audio running through a potentiometer. An
ST-VCA3 with external dc control provides virtual immunity from scratchy audio. Audio/video system control
units often provide 0 to 10 Vdc control outputs that can directly adjust audio levels using an ST-VCA3. The
ST-VCA3 is primarily intended for line-level attenuation although a high quality utility microphone preamplifier is
included in the module. If remote control of a microphone preamplifier is desired, such as a wall mounted level
control for a microphone jack, the ST-VCA3 may serve as a remote controlled microphone preamplifier.

The ST-VCA3 operates from a 24 Vdc ground-referenced power supply.

Wherever it is desirable to keep audio signal sources at an equipment location while providing compact, high
quality remote level control, the ST-VCA3 is the ideal choice. Use an ST-VCA3 and its associated remote
control individually or combine them with other RDL products as part of a complete audio/video system.

ASSOCIATED REMOTE CONTROL EXAMPLES:

► RLC10K and RLC10KS Wall mounted remote controls
► RLC10KM and RLC10KMS Wall mounted remote controls with muting
► RLC3 and RLC3S Remote control with preset levels
► RLC10R Rotary encoder remote control
► AMS-10K Linear potentiometer remote control

RDL  659 N. 6th St.  Prescott, AZ., USA 86301  [phone]  FAX [phone]  www.rdlnet.com

STICK-ON

®

SERIES

Model ST-VCA3

Voltage Controlled Amplifier

Installation/Operation

EN55103-1 E1-E5; EN55103-2 E1-E4

Typical Performance reflects product at public ation time
exclusive of EMC data, if any, supplied with product.
Specifications are subject to change without notice.

TYPICAL PERFORMANCE

Inputs (2): Mic: 200 Ω balanced; 5 kΩ unbalanced
Line: 30 k Ω balanced bridging or unbalanced
Input Levels: Mic: -60 dBu to -44 dBu (for +4 dBu output; 150 Ω source)
Line: -18 dBu (-20 dBV) to +4 dBu (for +4 dBu output)
Output Impedance: 150 Ω
Output Level: +4 dBu
Headroom: >18 dB
THD+N: Mic: < 0.05% (1 kHz, 50 dB gain)
Line: <0.025% (unity gain); 0.025% typical at 15 dB attenuation
Frequency Response: Mic: 30 Hz to 20 kHz (±1 dB)

Noise: Mic: < -70 dB below +4 dBu output (150 Ω source; 50 dB gain)
Line: <-78 dB below +4 dBu output (maximum gain); -90 dB at normal oper ating level
CMRR: Mic: > 60 dB (50 Hz to 120 Hz)
Line: > 60 dB (50 Hz to 120 Hz)
Attenuation Range: 0 to 90 dB (Attenuation >90 dB at 0 Vdc control
Control Voltage Output: 10 Vdc regulated; powers 10 kΩ potentiometer, RLC10K, RLC10KM or equivalent
VCA Control Input: 0 to 10 Vdc or 0 to 10 kΩ (Linear taper potentiometer), 200 kΩ
Indicators (3): Dual-LED VU meter (Green/Red); Level LED (Red) tracks VCA contr ol voltage
Power Requirement: 24 to 33 Vdc @ 50 mA, Ground-referenced
Dimensions: Height: 0.7 in. (1.7 cm), Width: 3 in. (7.6 cm ), Depth: 1.6 in. (3.9 cm)

Line: 10 Hz to 20 kHz (±0.1 dB)

Radio Design Labs Technical Support Centers

U.S.A. [phone], [phone]; Fax: [phone]

891-1160

Europe [NH Amsterdam] (++31) 20-6238 983; Fax: (++31) 20-6225-287