QSC Audio SPA-3 User Manual

SPA-3
Stereo
Precision
Attenuator

Owner’s

*TD-000100-00*

*TD-000100-00*

Manual

1

Rev. A

SPA-3 STEREO PRECISION ATTENUATOR

I. DESCRIPTION

The SPA-3 is a stereo preci­sion attenuator accessory
for use with DataPort­equipped 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 four­channel CX or DCA
amplifers) by using a
DataPort cable and a re­mote mounting rack. Ampli­fiers from the ISA series
cannot power the SPA-3, so
it requires a 15-volt exter­nal DC power supply when
used with one of them.

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Down

Shift

Up

Input
Stage

½

Micro-

controller

Signal
LED

Digital
Potentio­meter

8.8.

2-Digit
7-Segment
Display

To amplifier,
via DataPort

Output
Stage

Block diagram of one channel of the SPA-3

2

8.8.

8.8.

Kit contents

These parts are included along with your SPA-3 module:

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shield

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2PP-181040-CSwercskcalb"8/11×04-4#

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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).

SPA-3 input connections

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.

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

The terminal blocks plug into their respective jacks on the SPA-3.

both

the - and shield terminals for the shield.

Attaching the SPA-3 to the amplifier

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.

3

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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. Half­decibel settings are indicated by the right decimal point of the two-digit

n

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.

Attenuation display

Signal indicators

External DC power jack

SIGNAL

Inputs

CH 1

CH 2

15 V

300 mA

TRANSFORMER

ACCESSORY

SG-000005-AC

EXT. POWER

V. WARRANTY AND DISCLAIMERS

UPCH 1 ATTENUATION (dB) CH 2 ATTENUATION (dB)UP

other SHIFT +MUTE/UNMUTE =UP

SHIFT

INPUT

DOWN

SHIFT DOWN

INPUT

TRANSFORMER

BYPASS / ENGAGE = SHIFT + UP

0.5/1dBTOGGLE= SHIFT + DOWN

ACCESSORY

SG-000005-AC

XF-1 OPTIONAL

QSC AUDIO PRODUCTS INC.

COSTA MESA, CA USA

CH 1 INPUT CH 2 INPUT

XF-1 OPTIONAL

SPA-3

other SHIFT +

LOCK/UNLOCK channel = DOWN

SCROLL DOWN = press & hold DOWN

SCROLL UP = press & hold UP

DECR. SIGNAL = DOWN

INCR. SIGNAL = UP

STEREO PRECISION ATTENUATOR

The buttons, displays, and other features of the SPA-3

Up button

Down button

Shift button

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.

4

VI. TECHNICAL ASSISTANCE & 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: [e-mail]

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.

5

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

6

www.qscaudio.com