RDL STMA2 Data Sheet

STICK-ON® SERIES

Model ST-MA2
Muting Monitor Amplifier

ANYWHERE YOU NEED...

• A Single Speaker Monitor Amplifier

• A Conferencing Monitor Amp

• A Monitor Amp with Muting and Externally

Actuated Attenuation Steps

• Fast, Silent Audio Switching

• Multiple Control Inputs

• Adjustable Gain

You Need The ST-MA2!

The ST-MA2 is part of a group of products in the STICK-ON Series from Radio Design Labs. The durable
bottom adhesive permits quick, permanent or detachable mounting nearly anywhere or it may be used
with RDL’s racking accessories. The ST-MA2 offers the ultimate in totally solid-state muting and
attenuation switching, with the big plus, you can put it right where you need it!

APPLICATION: The ST-MA2 is a compact audio monitor amplifier with control inputs to mute or reduce
the gain of its output. This module may be used in conjunction with other RDL modules to configure
automatic mixing systems or may be used alone as a single speaker monitor amplifier. The ST-MA2 is
typically used to drive a small tabletop or overhead monitor speaker in a conference room, boardroom,
courtroom, public forum panel or similar installation. The ST-MA2 is ideally suited for use in automatic
mixing systems due to its control inputs.

The line-level input may be wired balanced or unbalanced. The audio output will drive standard speakers
from 4 to 45 ohms. Normal gain is preset by means of a trimmer on the module.

Five control inputs are provided. An open-collector, a switch closure, or compatible logic signals may
activate each. Typically, an RDL ST-GSP1 Gated Speech Preamplifier controls these inputs. There is a
control input which mutes the ST-MA2 output completely. This may be used to prevent feedback if there
is a pickup mic associated with the speaker driven by the ST-MA2. Two control terminals are provided to
attenuate the ST-MA2 output by 3 dB, and two additional terminals are provided to attenuate the output by
6 dB. These connect from the mic logic (or open-collector) control signals from gated mic preamps for
adjacent and second adjacent locations.

With muting, 3 dB, and 6 dB attenuation control inputs provided, the ST-MA2 is the ultimate in versatile
monitoring options in many multiple-mic environments.

RDL • P.O. Box 1286 • Carpinteria, CA., USA 93014 • [phone] • FAX [phone] • http://www.rdlnet.com

STICK-ON® SERIES

Model ST-MA2
Muting Monitor Amplifier

MUTING MONITOR AMPLIFIER

L
E

LINE INPUT

V
E

L

SIGNAL

FROM

UNBALANCED

LINE-LEVEL

SOURCE

L
E

LINE INPUT

V
E
L

PWR

OUTPUT

SPEAKER

MUTING MONITOR AMPLIFIER

PWR

OUTPUT

GAIN REDUCTION GAIN REDUCTION

M
U

- 6 - 3

- 6dB- 3dB- 3

dB

T

dBdB

E

GAIN REDUCTION

M
U
T
E

- 3 - 6

dB dB

- 6

dB

Installation/Operation

L
E

LINE INPUT

V
E
L

SIGNAL

FROM
BALANCED
LINE-LEVEL

SOURCE

L
E

MIC INPUT

V
E
L

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

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

MUTING MONITOR AMPLIFIER

PWR

OUTPUT

- 6

dB

M
U

- 6- 3- 3

T

dBdB

dB

E

24 VDC

POWER

SOURCE

GATED SPEECH PREAMPLIFIER

PHNTM PWR

LINE LEVEL OUTPUT

24V

S
L

DC

A

OUT

V
E

G

D
EOUTPUT

A

L

T

A
Y

E

OPEN

COLLECTOR

OR

MANUAL

ACTUATION

CONNECT TO OTHER ST-GSP1s

OR OTHER DEVICES

TYPICAL PERFORMANCE

Input Impedance: 20 kΩ balanced or unbalanced bridging
Input level: -10 dBv minimum for 2 Watts RMS output
Output Impedance: 8 Ω (will drive 4 Ω loads)
Output Power: 1.75 Watts RMS continuous; 2 Watts RMS max.
THD + N: < 0.500%
Bandwidth: 45 Hz to 14 kHz
CMRR: > 60 dB (50 Hz to 120 Hz)
Residual Noise: < -80 dB below 2 Watts RMS
Switching Time: < 50µs
Attenuation (Muted): > 90 dB @ 1 kHz
> 85 dB 300 Hz to 3 kHz
> 75 dB 20 Hz to 20 kHz
Selectable Attenuation: 3 or 6 dB, each setting individually selectable using two independent inputs
(connect to ground to activate)
Power: 24 to 33 Vdc @ 200 mA, Ground-referenced, for rated output
(220 mA for 2 Watts RMS)

Radio Design Labs Technical Support Centers

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

891-1011H

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