QSC SPA-3 User manual

PERFORMANCE ACCESSORIES
1675 MacArthur Boulevard
Costa Mesa, CA 92626
Ph: 800/854-4079 or 714/957-7100
Fax: [phone]
www.qscaudio.com
SPA-3
Stereo Precision Attenuator
Basic Description
The SPA-3 is an externally mounted two-channel precision attenuator
accessory for DataPort-equipped QSC amplifiers. With pushbutton pro-
gramming and digital gain control, it offers precise, secure, and repeat-
able attenuation settings from 0 to 32 dB. It features optional input iso-
lation transformers custom-made for QSC by Jensen, providing superb
common-mode noise rejection for high-performance sound systems.
The SPA-3 mounts directly to the rear panel of two-channel CX, DCA,
and PowerLight 2 Series amplifiers. For use with four-channel models or
with PowerLight amplifiers, the accessory can be mounted on an acces-
sory rack-mount panel and connected to the amplifier via a VGA-type
extension cable (with pin 9). See below for a more detailed list.
Compatible amplifier models
•Two-channel CX, DCA, and base PL2 models
•Four-channel CX and DCA models (via connecting cable)
•ISA models
•PowerLight models (via DPX-2 connecting cable and with DPX-1
external power supply; use DPX-4 accessory mounting bracket)
Features
•Precisely attenuates signal up to 32 dB in increments as small as 0.5 dB
•Selectable increment scaling: 0.5 or 1 dB
•Low-noise, low-distortion, high-performance digital gain controls
•DataPort connectivity
•Balanced “Euro-style” inputs
•Optional high-performance input transformers to precisely balance
and isolate amplifier inputs for superb noise rejection
•Channels can be independently muted, bypassed, or locked
•Easy to install
Specifications subject to change without notice.
SPA-3, shown with optional XF-1
transformers installed

QSC Audio Products, Inc. 1675 MacArthur Boulevard • Costa Mesa, CA 92626 • Ph: 800/854-4079 or 714/957-7100 • Fax: [phone] • www.qscaudio.com
Specifications subject to change without notice.
SPA-3 SPECIFICATIONS
GENERAL INFORMATION
Attenuation
PROGRAMMABLE OPERATING PARAMETERS
DataPort
0 to 32 dB in 0.5- or 1.0-dB increments
HD15 male (to amplifier); HD15 female (to QSControl system)
External power Coaxial jack
Bypass, Mute, or Lock Either channel
SPA-3
Operating temperature 0–70° C
Input type, each channel Differential balanced (transformer balancing optional)
Input impedance 28.4 k
ΩΩ
balanced, 14.7 k
ΩΩ
unbalanced
Output impedance, main 95
ΩΩ
, quasi-balanced
+18 dBu
Noise (0 dBr = maximum output) -116 dBr
THD @ +4 dBu out <0.01% @ 1 kHz
Frequency response 20 Hz–20 kHz, ±0.2 dB
Common-mode rejection >50 dB minimum; >60 dB typical
CONTROLS
Programming Pushbutton switches for incremental programming: Shift, Up, and Down
INDICATORS
Attenuation (each channel) 2-digit 7-segment LED display
Signal presence (each channel) Green LED
CONNECTORS
Input (two channels) 5-pin “Euro-style” detachable terminal block
+15V @ <300 mA, via external power jack, or from amplifier via pin 9 of DataPort
Power requirements
Maximum RMS output voltage
0.5 dB indicator (each channel) Decimal point
Up
Down
Shift
½Micro-
controller
8.8.
Digital
Potentio-
meter
2-Digit
7-Segment
Display
Input
Stage
Output
Stage
Signal
LED
To amplifier,
via DataPort
8.8. 8.8.
Block diagram of SPA-3 (one channel shown)
Mounting the SPA-3 to a two-channel
CX, DCA, or PL2 amplifier
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