RDL RUPA40D Quick Start Guide

RACK-UP® SERIES

Model RU-PA40D

40 W Stereo Audio Power Amplifier
with VCA Control and Power Supply

• VCA Controlled Stereo Audio Power Amplifier

• 20 W RMS / Channel into 8 Ω – 40 Watts Total

• 15 W RMS / Channel into 4 Ω – 30 Watts Total

• Unbalanced Inputs on RCA Phono Jacks

• Balanced Inputs on Detachable Terminal Block

• Switch-Selectable Stereo or Mono Operation

• VCA Control on Detachable Terminal Block

• Compatible with RDL Remote Level Controls

• External Control Using 10 KΩ Potentiometer or 0 to 10 Vdc

• Compressor/Limiter Controls Clipping

• Studio Quality, Aurally Transparent Compressor/Limiter

• Compressor Produces Maximized Average Output Power

• Compression Enabled Using Input Level Adjustments

• LED to Indicate Audio Compression Threshold

• High-Efficiency Class D Operation

• Thermal and Short-Circuit Protection

The RU-PA40D is a utility power amplifier in the convenient line of RACK-UP products, featuring the superior engineering and components
common to RDL products. The RU-PA40D may be rack or surface mounted with optional RACK-UP series accessories. The RU-PA40D gives you
the advantages of a quality, high efficiency stereo audio power amplifier with the added convenience of remote control!

APPLICATION: The RU-PA40D is the ideal choice in many applications where a high quality, high-efficiency utility amplifier is needed to
drive a pair of 4 Ω or 8 Ω speakers. It is specifically suited to amplification applications where users need to adjust the gain. Examples
include projectors or monitors with fixed audio outputs used in classrooms, boardrooms and video conferencing. The RU-PA40D is ideal
for foreground sound amplification in small to medium rooms or in a specific zone within a retail space.

The RU-PA40D features two balanced line-level inputs on a detachable terminal block. Two unbalanced line level inputs are available on
high-reliability gold plated phono (RCA) jacks. A front-panel gain control trimmer permits setting the maximum gain for each channel. The
gain range accommodates the range of typical balanced and unbalanced audio signal levels. Each of the two RU-PA40D outputs will drive
a 4 Ω or 8 Ω speaker or multiple speakers connected to present a 4 Ω or 8 Ω load to the amplifier. The output impedance is
switch-selectable on the front panel of the module.

The RU-PA40D is equipped with an internal stereo VCA for setting the output level on both amplifier channels. A detachable terminal
block provides for the connection of an external 10 KΩ potentiometer or a 0 to 10 Vdc control voltage. RDL remote controls are available to
provide single-turn, multi-turn (rotary encoder) or pushbutton (ramp or fixed level selection) user level control. VCA control insures long
term noise-free level adjustment. Remote control is possible using audio, control or common computer network wire.

A front-panel switch is provided to sum the audio inputs to mono. In the STEREO mode, the RU-PA40D independently amplifies each
audio channel, left (L) and right (R). If speaker placement in the specified installation is incompatible with stereophonic amplification, the
INPUT MODE switch may be set to SUMMED MONO.

The RU-PA40D includes a stereo analog compressor/limiter for audio fidelity noticeably superior to conventional class D amplifiers with
digital limiting. The input GAIN settings determine whether the limiter alone is used for clipping suppression, or if the full compressor/limiter
will be used to substantially increase the average output power beyond that of a standard 40 W amplifier. A red front-panel LED flashes
when the limiter is preventing output clipping. Normal audio level signals remain unaffected by the compressor thereby preserving audio
dynamics. If the input level is increased so that the compressor is active, the LED remains dimly lit between peak flashes. The audio is
compressed according to three dynamic time constants providing aural transparency while maintaining clean, unclipped amplified audio for
input overloads of up to 20 dB. The RU-PA40D, with compression, is capable of producing average audio output levels and clarity normally
expected from stereo amplifiers with a much higher output power rating.

A blue POWER LED illuminates when the RU-PA40D is powered from its external 24 Vdc power supply (included). The module is
equipped with both thermal and output short-circuit protection. The high-efficiency Class D output stages produce minimal heat for all
levels of expected voice or music modulation. Continuous full-power operation with audio tones will not damage the amplifier, but is not
recommended.

Wherever an ultra-compact, high quality, high efficiency audio power amplifier is needed to provide reliability and unsurpassed versatility,
the RU-PA40D is the ideal choice. Use the RU-PA40D individually, or combine it with other RDL products as part of a complete
audio/video system.

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

TYPICAL APPLICATIONS:

► Projector-Mounted Amplification
► Boardrooms
► Classrooms
► Restaurant or Residential Patios
► Audio / Visual Carts
► Video Conferencing
► Localized Stereo Sound
► Foreground Sound in Retail Store Zone

RACK-UP

Model RU-PA40D

40 W Stereo Audio Power Amplifier
with VCA Control & Power Supply

Mounting
The RU-PA40D should be mounted in a location with good ventilation. If the module is mounted using a box that does not provide ventilation, the amplifier should be secured to the outside
surface of the box using the two mounting screws provided. The spacing between the mounting screws is 5.3 in. (13.46 cm); the recommended hole diameter is 0.187 in. (.475 cm). The ambient
operating environment must not exceed 40 degrees C.

Connection and Adjustment

1. Set the GAIN controls fully counter-clockwise.

2. Connect the audio inputs, speakers and 24 Vdc (2 A minimum) power supply.

3. Connect an external dc ramp generator, 10 K potentiometer or RDL remote control to the VCA input.

4. Set the VCA external control to its maximum level.

5. Set the OUTPUT IMPEDANCE switch (4 or 8 Ohms) corresponding to the speaker load.

6. For overshoot protection only, adjust the two GAIN controls for the desired audio level

7. For maximum audio output level with compression, increase the two GAIN controls for

8. If summed mono operation is desired, set the INPUT MODE switch to SUMMED MONO.

®

SERIES

with the THRESHOLD LED flashing only occasionally on audio peaks.

the desired audio level with the THRESHOLD LED lit dimly between peak flashes.

CONNECT TO RDL RLC3 TO PROVIDE PUSHBUTTON
USER SELECTION OF PRE-DEFINED AUDIO LEVELS

CONNECT TO RDL RLC10K TO PROVIDE

USER CONTROL OF AUDIO LEVELS

Installation/Operation

CONNECT TO ANY 10 K OHM LINEAR TAPER
POTENTIOMETER FOR LEVEL ADJUSTMENT

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.

CONNECT TO ANY ZERO-TO-TEN VOLT

DC RAMP GENERATOR TO CONTROL AUDIO LEVEL

LINEAR TAPER

24Vdc

CTRL

RDL

RLC3

NORM

SET

LEVEL

LOW

MIN

REAR REAR

AUDIO SOURCE CONNECTIONS

UNBALANCED

BALANCED

10 V OUT

0-10 V IN

VCA VCA

WER

CTRL

LEFT

L

OUTPUT

RIGHT

OUTPUT

SET INPUT MODE SWITCH T O "STEREO" FOR STE REO OPERATION

SET INPUT MODE SWITCH TO "SUMMED MONO" TO COMBINE
THE LEFT AND RIGHT INPUT SIGNALS TO MONO. NOTE THAT

THE "L" AND "R" GAIN CONTROLS WILL STILL INDEPENDENTLY

ADJUST THE LEFT AND RIGHT SPEAKER OUTPUT LEVELS.

ADJUST LEFT OUTPUT LEVEL

10 V OUT

0-10 V IN

LEFT

OUTPUT

OUTPUT

LEFT

RIGHT

VCA
CTRL

WER

L

UNBALANCED

R

RIGHT

ADJUST RIGHT OUTPUT LEVEL

THE RED LED FLASHES WHEN THE LIMITER PROVIDES CLIPPING PROTECTION

AND WILL REMAIN DIMLY LIT IF THE AUDIO INPUT GAIN IS INCREASED

TO CAUSE THE COMPRESSOR TO PRODUCE HIGHER AVERAGE OUTPUT POWER.

L

L

GAIN

INPUTS

R

R

WIRING FOR TWO 8 OHM SPEAKERS PER CHANNEL CONNECTED AS A 4 OHM LOAD

8 OHM

TYPICAL PERFORMANCE

Inputs (4): Line level: Balanced (+4 dBu) Left and Right, Unbalanced (-10 dBV) Left and Right
Input Impedance: 50 kΩ balanced, 20 kΩ unbalanced
Gain Adjustments (2): Single turn, one per channel
Minimum Input Levels: -11 dBu balanced, -18 dBV unbalanced (to cross compressor thr eshold)
Maximum Input Levels: +22 dBu balanced, +12 dBV unbalanced
VCA Control: External 0 to 10 Vdc (linear), 10 KΩ linear taper potentiometer, RDL remote contr ols
10 Vdc VCA reference voltage output provided
Frequency Response: 20 Hz to 20 kHz (+/- 1 dB, 4 or 8 Ohms)*
THD+N: < 0.1% (1 kHz, 1 W, 4 or 8 Ohms); < 1% (50 Hz to 20 kHz,)*
*measured at compressor threshold level equaling 12 W RMS (8 Ohms) output power
Compressor: Thr eshold nominally 2 dB below rated output, automatically adjusting attack and release times
Crosstalk: Better than 60 dB (1 kHz, no compression)
Noise (below 20 W RMS): <-80 dB (VCA control at 6.25V; output level 6 dB below max.) < -70 dB (VCA control at max.)
Selectors (2): Slide switches: Output Impedance 4 Ohms or 8 Ohms; Input Mode SUMMED MONO or STEREO
Output Power: 20 W RMS into 8 Ω per channel, 40 W RMS total; 15 W RMS into 4 Ω per channel, 30 W RMS total
Output Circuit: Class D
Ambient Operating Environment:
Indicators (2): Red LED: THRESHOLD LED indicates compressor activity
Blue LED: POWER on
Power Supply (included): 100 to 240 Vac, 50-60 Hz, 1.5A; 24 Vdc output to module

RIGHT

0° C to 40° C Maximum; 20° C Recommended

10 V OUT

0-10 V IN

VCA
CTRL

10K

L

CCW
(OFF)

BLUE LED INDICATES WHEN POWER

SUMMED MONO

STEREO

INPUT MODE

SET THE OUTPUT IMPEDANCE SWITCH TO 4 OHMS

COMPRESSOR/LIMITER

THRESHOLD

4 OHMS (2 x 15W)

8 OHMS (2 x 20W)

OUTPUT IMPEDANCE

SET OUTPUT IMPEDANCE SWITCH TO MATCH

THE IMPEDANCE OF THE CONNECTED LOADS.

NOTE: INCORRECT SETTING MAY PRODUCE DISTORTION

8 OHM8 OHM

LEFT

10 V OUT

0-10 V IN

CTRL

L

IS CONNECTED TO MODULE

24 VDC

POWER

LEFT

OUTPUT

RIGHT

OUTPUT

Radio Design Labs Technical Support Centers

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

891-3305

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

0 TO 10 V

RDL OR

OEM RAMP

GENERATOR

10 V OUT

0-10 V IN

VCA
CTRL

L

LEFT

4 OR 8 OHM

24 VDC, 2 A MIN

POWER

SOURCE

4 OR 8 OHM

RIGHT

8 OHM

LEFTRIGHT

Models

includes:

RU-PA40D

Amplifier, Power Supply, North American Power Cord

RU-PA40DE includes:
Amplifier, Power Supply (without Power Cord)