QSC SPA-3 User manual

1
*TD-000100-00*
*TD-000100-00*
Rev. A
Owner’s Manual
SPA-3
Stereo
Precision
Attenuator

2
I.DESCRIPTION
The SPA-3 is a stereo preci-
sion attenuator accessory
for use with DataPort-
equipped QSC amplifiers. It
mounts directly to the back
of two-channel CX, DCA, and
PL2 models, but it can be
used with the others
(PowerLight, ISA, and four-
channel CX or DCA
amplifers) by using a
DataPort cable and a re-
mote mounting rack. Ampli-
fiers from the ISA series
cannot power the SPA-3, so
it requires a 15-volt exter-
nal DC power supply when
used with one of them.
SPA-3 STEREO PRECISION ATTENUATOR
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Up
Down
Shift
½ Micro-
controller
8.8.
Digital
Potentio-
meter
2-Digit
7-Segment
Display
Input
Stage
Output
Stage
Signal
LED
To amplifier,
via DataPort
Block diagram of one channel of the SPA-3

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8.8. 8.8.
III.INSTALLATION
CAUTION: Always turn the amplifier off when installing or removing the SPA-3.
Connecting inputs
The signal wires attach to each “Euro-style” terminal block as
shown in the illustration at the top of this page. Pay attention to
signal polarity. Strip the wires approximately 0.35 inch (9 mm). The
screw head above each terminal opens and closes its clamp; after
inserting the wire in the terminal, tighten the clamp firmly.
If the input signal is unbalanced, use the + terminal for the signal
conductor and both the - and shield terminals for the shield.
The terminal blocks plug into their respective jacks on the SPA-3.
PowerLight 2 and two-channel CX, DCA amplifiers
Line up the SPA-3’s DataPort connector with the one on the amplifier’s rear panel. Press the SPA-3 onto the amplifier and secure
it to the chassis with the three screws included (see the illustration above).
PowerLight, ISA, and four-channel CX and DCA amplifiers
An SPA-3 will not physically mount on one of these amplifiers. A DPX-4 accessory bracket, however, can hold up to four SPA-3
units. Use a DataPort cable to connect the SPA-3 to the amplifier. The SPA-3 will draw the power it needs from the DataPort of
PowerLight, CX and DCA amplifiers, but if used with an ISA series amplifier, it will require an external 15-volt DC power supply
capable of 300 mA, such as a QSC DPX-1.
II.FEATURES
The heart of the SPA-3 is a Crystal Semiconductor digitally controlled dual-channel gain control. The user controls are pushbuttons
for adjusting the amount of attenuation, for bypassing (unity gain), for changing the adjustment increment, and for displaying the
firmware version.
Both channels feature electronically balanced input circuitry. The pseudo-balanced outputs connect to the amplifier through the
DataPort. The attenuation can be adjusted from 0 to 32 dB and can also be bypassed. A green LED for each channel indicates that
its pre-attenuation circuitry is passing a signal. The settings are non-volatile and are retained when the amplifier is turned off.
To improve common-mode noise rejection, an optional XF-1 input isolation transformer can be installed on each channel by a
qualified technician.
The screws are for mounting the SPA-3 to an amplifier or accessory bracket (see INSTALLATION), and the two plugs are detachable
terminal blocks for the SPA-3’s two balanced inputs (see the illustration above).
Kit contents
These parts are included along with your SPA-3 module:
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1PP-150080-CSwercskcalb"61/5×23-8#
shield
SPA-3 input connections
Attaching the SPA-3 to the amplifier

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V.WARRANTYANDDISCLAIMERS
Disclaimer
QSC Audio Products, Inc. is not liable for any damage to speakers, amplifiers, or any other equipment that is caused by negligence
or improper installation and/or use of the SPA-3.
Product Warranty
QSC Audio Products, Inc. guarantees the SPA-3 to be free from defective material and/or workmanship for a period of three years
from date of sale, and will replace defective parts and repair malfunctioning products under this warranty when the defect occurs
under normal installation and use—provided the unit is returned to our factory via prepaid transportation with proof of purchase
(sales receipt). This warranty provides that examination of the returned product must disclose, in our judgment, a manufacturing
defect. This warranty does not extend to any product which has been subject to misuse, neglect, accident, improper installation,
or where the date code has been removed or defaced.
CH 1 INPUT CH 2 INPUT
SIGNAL
CH 1
CH 2
300 mA
15 V
EXT. POWER
SPA-3
STEREO PRECISION ATTENUATOR
SHIFT DOWN
UPCH 1 ATTENUATION (dB) CH 2 ATTENUATION (dB)UP
SHIFT
INPUT
TRANSFORMER
ACCESSORY
SG-000005-AC
XF-1 OPTIONAL
INCR. SIGNAL = UP
DECR. SIGNAL = DOWN
SCROLL UP = press & hold UP
LOCK/UNLOCK channel = DOWN
SCROLL DOWN = press & hold DOWN
other SHIFT +
INPUT
TRANSFORMER
ACCESSORY
SG-000005-AC
XF-1 OPTIONAL
BYPASS / ENGAGE = SHIFT + UP
other SHIFT +MUTE/UNMUTE =UP
0.5/1dBTOGGLE = SHIFT + DOWN
QSC AUDIO PRODUCTS INC.
COSTA MESA, CA USA
DOWN
Up button
Down button
Shift button
Attenuation display
Signal indicators
External DC power jack
Inputs
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IV.OPERATION
The table at left shows the button sequences for all possible operations on the
SPA-3.
The adjustable range of attenuation on each channel is 0 (no attenuation) to
32 dB. The attenuation changes in real time as you make the adjustments. Half-
decibel settings are indicated by the right decimal point of the two-digit
display. For example, a display of indicates a setting of 18 dB of attenuation,
while would indicate 18.5 dB. Even when its DC power is removed, the SPA-3
will retain its settings in non-volatile memory.
The buttons, displays, and other features of the SPA-3

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VI.TECHNICALASSISTANCE&SERVICE
Only a qualified technician should service your QSC product. There are no user serviceable components inside the unit and the
risk of electric shock exists. Also, some components in your unit may require specific QSC replacements.
Technical Assistance
If you suspect that your SPA-3 is defective, check your system configuration and SPA-3 settings to determine the origin of the
problem. Incorrect audio interfacing, poor cabling, or other system-level defects are the most frequent causes of problems in audio
systems. For technical assistance beyond the scope of this manual, contact QSC Technical Services. We also offer comprehensive
service manuals for many QSC models; contact us for details.
Factory Service
If your SPA-3 needs factory service, contact QSC Technical Services for return instructions. We will issue you a Return
Authorization (RA) number for each unit. QSC cannot be responsible for products that are returned without an RA number.
Product Return Guidelines
1. Pack the product well for protection during shipment. Upon request, QSC will provide a factory shipping carton and
packaging free of charge.
2. Include a copy of the sales receipt, your name, return address, and phone number with your return correspondence.
Please include a reasonably detailed description of the defect.
3. Call QSC Technical Services for a Return Authorization number.
4. Mark the Return Authorization number on the outside of the packaging.
5. Ship the product prepaid to QSC Technical Services at the address listed below. We recommend United Parcel Service
(UPS).
QSC Technical Services
1665 MacArthur Blvd.
Costa Mesa, California 92626 USA
Web: www.qscaudio.com (product info and support)
www.qscstore.com (service and accessory sales)
E-mail: [email protected]
Telephone: [phone] (USA only)
[phone]
[phone]
Fax: [phone]
Bulletin Board: [phone]
Qualified Service Centers
For your convenience, QSC maintains a network of qualified service centers. If you wish to take your QSC product to a local service
center, you may call QSC Technical Services for a referral for one near you. However, accessories, input modules, and other
peripheral QSC products must be returned to the QSC factory for service.
International Servicing
For service on QSC products purchased outside of the United States, contact the distributor or dealer in the country where the
product was originally purchased. In many countries, the distributor or dealer may also refer you to a qualified service centers.
QSC Technical Services can help you contact the distributor in your country.

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“QSC”and the QSC logo are registered trademarks of QSC Audio Products, Inc. 1675 MacArthur Blvd. Costa Mesa, CA 92626 [phone] FAX [phone]
www.qscaudio.com