DSP-4 Digital Signal Processor - AV-iQ
Digital Signal Processor
Amplifier Accessory Hardware Manual
The lightning flash with arrowhead symbol,
within an equilateral triangle, is intended to
alert the user to the presence of uninsulated
“dangerous voltage” within the product’s enclosure that may be of sufficient magnitude to
constitute a risk of electric shock to humans.
The exclamation point within an equilateral
triangle is intended to alert the users to the
presence of important operating and maintenance (servicing) instructions in the literature accompanying the product.
CAUTION: To reduce the risk of electric shock, do not
remove the cover. No user-serviceable parts inside. Refer
servicing to qualified service personnel.
WARNING: To prevent fire or electric shock, do not expose
this equipment to rain or moisture.
Electrical energy can perform many useful
functions. This unit has been engineered
and manufactured to assure your personal
safety. Improper use can result in potential
electrical shock or fire hazards. In order not
to defeat the safeguards, observe the following instructions for its installation, use
and servicing.
•Maximum operating ambient temperature
is 50° C.
•Never restrict the airflow through the
device’s fan or vents.
•When installing equipment into a rack,
distribute the units evenly. Otherwise hazardous conditions may be created by an
uneven weight distribution.
•Connect the unit only to a properly rated
supply circuit.
Federal Communications Commission (FCC)
NOTE: This equipment has been tested and found to comply with the
limits for a Class B digital device, pursuant to Part 15 of the FCC Rules.
These limits are designed to provide reasonable protection against
harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed
and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that
interference will not occur in a particular installation. If this equipment
does cause harmful interference to radio or television reception, which
can by determined by turning the equipment off and on, the user is
encouraged to try to correct the interference by one or more of the
following measures:
- Reorient or relocate the receiving antenna.
- Increase the separation between the equipment and the receiver.
- Connect the equipment into an outlet on a circuit different from that to
which the receiver is connected.
- Consult the dealer or an experienced radio/TV technician for help.
•Reliable Earthing (Grounding) of rackmounted equipment should be maintained.
While QSC has endeavored to develop and produce the most dependable and robust Digital Signal Processor (DSP) audio product for your
use, due to the unlimited and potentially destructive (to the sound system) configurations that may be applied to the DSP by the user, QSC
cannot be held responsible for damages resulting from any deviation or failure by the user to strictly follow the recommendations set forth
in the owner’s manual for the integration of the DSP-4 and Signal Manager software with your sound system.
All risks attendant to integration of user-configurable DSP products with your sound system are assumed by you. While QSC strives to supply
the highest quality technical solutions for Digital Signal Processing, in no event will QSC or its suppliers be held liable for any damages,
consequential, incidental, or otherwise, including any claims for lost profits and/or savings resulting from any attempted integration of the
DSP-4 and Signal Manager software which does not strictly adhere to the manual’s recommendations.
Warnings, Explanation of Graphical Symbols, and FCC Statement..............................................................2
Connector & Indicator Descriptions, Illustrations.................5
Functions and Features..........................................................7
Block Diagram..........................................................................................8
What is Included, What else May be Needed.....................................9
Signal Manager Software Installation........................................10
Mounting to QSC DataPort Equipped Amplifiers...............................11
Mounting to the Accessory Remote Mounting Bracket......................12
Connecting to the DataPort of the DSP-4..............................................13
Connecting XLR Audio Inputs and Outputs......................................14
Connecting to RS-232 Port........................................................................15
Connection to Accessory External DC Power Supply.................16
Daisy-chaining the DSP-4 Outputs.........................................................17
General Guidelines for Freely Configurable DSP....................................18
Special Information About Saving DSP-4 Configurations.....19
SPECIFICATIONS.............................................. ...........................................................................................20
ARCHITECT’S & ENGINEER’S SPECIFICATION .....................................................................................22
DataPort Pinout.........................................................................................23
RS-232 Pinout ............................................................................................24
XLR Connector Pinout ...............................................................24
Application Information...............................................................25
Maintenance, Warranty & QSC Contact Information................................26
© Copyright 2002, QSC Audio Products, Inc.
QSC® is a registered trademark of QSC Audio Products, Inc., Costa Mesa, CA
“QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office
Overview of the DSP-4
The DSP-4 is a digital signal processor (DSP ) accessory for
4 is mounted remotely on a rack-mount accessory bracket
audio power amplifiers. It is designed to reduce the need for
providing a solid mounting platform. There are two LED’s; blue
external signal processing while increasing overall system
to indicate power status and green to indicate input signal
reliability through distributed intelligence. It is intended prima-
rily for QSC’s CX, DCA, and Powerlight2 series amplifiers and
mounts directly to the rear panel of the 2-RU, 2-channel models
of these amplifiers (pre-August, 1999 date-code of the CX, DCA
and Powerlight2, and all ISA models will require use of an
external power supply). Use of the DSP-4 with Powerlight
models requires remote mounting, external power supply and
Connections include an RS-232 port and a DataPort passthrough connector for use with QSC DataPort products . For nonDataPort applications, two XLR audio inputs and two XLR
outputs (post-DSP) are provided. There is a power receptacle for
use with amplifiers that do not provide DataPort power or with
non-QSC amplifiers.
use of a special interconnect cable (PL6.0/9.0 only). Refer to the
Appendix for application information. The DSP-4 can also be
used with amplifiers that do not have a QSC DataPort (older QSC
models, non-QSC models) with a reduced feature set and
remote mounting/external power.
Control of the DSP-4 is accomplished with the supplied QSC
Signal Manager software and an RS-232 connection between
the module and PC. The Signal Manager software provides an
easy-to-use graphical user interface where DSP “objects” are
placed onto a palette and connected. This interface allows for
The signal processing capabilities include Compressors,
Limiters, multiple Parametric Filters, High- and Low-Pass Filters, Shelf Filters, Muting, Attenuation, Multiple Delays, Polarity Reversal, and Audio Routing. A new feature of the DSP-4 is
amplifier output Power Limiting (QSC DataPort amplifiers only).
Analog-to-digital and digital-to-analog converters are 24-bit
almost infinite configuration possibilities. Once the DSP-4 has
been set up as desired and the configuration saved to the DSP4, connection to the PC is no longer required. This feature
allows essentially tamper-proof amplifier DSP setup. Further
changes can be implemented in the field by simply connecting
a PC and loading the new setup into the DSP-4.
resolution and 48 kHz. sampling rate. Post-processor audio
outputs are daisy-chainable for connection to additional amplifiers. Input sensitivity and output level is software selectable.
Dynamic range is greater than 106 dB. Inputs are balanced and
the post-DSP outputs are pseudo balanced.
Physically, the DSP-4 is a small module that “piggybacks”
onto the back panel of the specified QSC amplifiers. It connects
directly to the DataPort on the back panel and is secured with
supplied hardware. When used with other amplifiers, the DSP-
Operation over an Ethernet network can be accomplished using
QSC’s QSControl platform. Please refer to the software documentation (software Help file and Readme.txt file) for supported feature-set and operation information.
From all of us at QSC Audio, thank you for your purchase. Be sure
to check our website at http://www.qscaudio.com for the
latest software and firmware updates as well as sample DSP
INTRODUCTION- Connector & Indicator Descriptions
Front Panel
CH 1 INPUT, CH 2 INPUT: balanced female
CH 1 OUTPUT, CH 2 OUTPUT: pseudo-bal-
XLR’s. If not using the DataPort for inputs, these
anced male XLR’s. These outputs provide post-
are where you connect the line-level audio inputs
DSP (processed) signal from the DSP-4 for down-
to the DSP-4.
stream devices (amplifiers, monitoring busses,
daisy-chaining the processed signal to a second
They are electronically balanced with an input
amplifier). When using with non-DataPort ampli-
impedance of 8.3k Ohms. If used in an unbal-
fiers, these outputs should be connected to your
anced configuration, the input impedance is 3.7k
amplifier’s input connectors.
Ohms. Input sensitivity is software selectable.
SIGNAL indicator-:This green
LED illuminates when the
DSP-4 detects an input signal
2.5mm barrel connector-
on either channel. Dual bright-
Center (+), Outer(-), 15
ness levels indicate signal
VDC, 300 mA. Use if your
level. At -40dB fs, it will light
amplifier does not sup-
dimly; at -20dB fs it will light
ply the required operat-
ing voltage from its
RS-232: DB-9 female jack. Use
for serial cable connection between the DSP-4 and the computer. Connection is required only
for setup and real-time control of
DATAPORT: This is the “in-
the module. Connection need not
put” DataPort. If using with QSC
be maintained for use.
DataPort products that supply
audio inputs or provide amplifier control & monitoring, this
is where they are connected. If
POWER indicator: This blue
Chassis Lance - Use this lance
using this DataPort for audio
LED illuminates when the mod-
to secure accessory power cord
inputs, do not apply input sig-
ule has power properly applied.
(if used) with a wire tie.
nal to the XLR inputs.
INTRODUCTION- Connector & Indicator Descriptions
Rear Panel
DATAPORT (unlabeled): This is the “output”
If the DSP-4 is directly mounted on a 2-RU, 2
channel QSC DataPort equipped amplifier, this
connector plugs into the amplifier’s DataPort connector.
If used with 3-RU, 4- or 8-channel QSC DataPort
equipped amplifiers, the DSP-4 module will need
to be remotely mounted and a male-female
DataPort cable used to interconnect the amp &
If used with a non-DataPort amp (QSC or other),
this connector will not be used.
INTRODUCTION- Functions & Features
DSP-4 Hardware Features
The full set of features is available on QSC DataPort equipped amplifiers connected to the DSP module via the DataPort connector
(direct-connect or remote-mount with DPX-2 cable). “V2” DataPorts and non-QSC amplifiers do not support Output Power Limiting.
Parametric EQ
Adjustable frequency
Adjustable gain
Adjustable Q factor
Ability to bypass all EQ with a single mouse click
Ability to add or delete EQ
Graphical response curve provided in software
Assignable anywhere in the signal chain
Signal Compressor
Adjustable attack and release times
Adjustable Gain
Adjustable threshold
Adjustable compression ratio
Graphical response curve provided in software
Assignable anywhere in the signal chain
Signal Level Meter (peak or RMS response)
High- and Low-Pass Crossover
Selectable responses:
Butterworth (6,12,18 or 24 dB/octave slope)
Bessel (6,12,18 or 24 dB/octave slope)
Linkwitz-Riley (12 or 24 dB/octave slope)
Graphical response curve provided in software
Adjustable frequency & slope
Ability to bypass all EQ with a single mouse click
Ability to add or delete EQ
Assignable anywhere in signal chain
High- and Low-Pass Shelf Filter
Adjustable corner frequency
Adjustable Q factor
Adjustable gain
Graphical response curve provided in software
Ability to bypass all EQ with a single mouse click
Ability to add or delete EQ
Assignable anywhere in signal chain
Signal Attenuation (mute or bypass)
Output Gain up to +12 dB
2 to 1 Mixer
Output Power Limiter (QSC DataPort Amps)
Select QSC amplifier model for tailored results
Graphical response curve provided in software
Ability to quickly bypass limiter with a single mouse click
Directly monitors amplifier output voltages and currents
Signal Splitter
External Contact Closure Sensing
Pink & White Noise Generator
Multiple Delays
910 millisecond maximum (sum of all delay objects)
20.83 microsecond increments
Entry can be in seconds, feet or meters
Assignable anywhere in signal chain.
Variable Frequency Tone Generator
Clip & Protect Indication
Signal Polarity Reversal
“V2” DataPort amplifiers and non-QSC amplifiers do not support Output Power Limiting.
INTRODUCTION- Block Diagram and Details
This portion of the introduction provides some of the technical details of the DSP-4.
Input Stage- Inputs are electronically balanced and RF filtered. The input sensitivity is software-selectable and any large
signals are prevented from destroying the A-to-D by a diode.
Output Stage- The output is buffered and then filtered to remove high-frequency sampling artifacts. Output sensitivity is
software-selectable and available from both sets of outputs simultaneously.
Data Acquisition- The data acquisition A-to-D samples the output voltage and current of both amplifier channels. This
data is used for amplifier output power limiting. Amplifier clip and protect-mode status data is also sampled. Power, protect/
clip indication, and output power limiting is not possible on non-DataPort amplifiers or “V2” DataPort amplifiers.
Contact Closure Trigger Input- Pin 9 of the RS-232 can be used as a trigger input for operating software “objects”,
such as “Switched Gain”. It’s TTL compatible: pulling this pin to ground through a maximum impedance of 1.3k ohms forces a
general I/O pin of the DSP to a logic-low condition. The Signal Manager software can use this “event” to change gain
settings or Preset mode. Refer to the Signal Manager software Help file for available applications of the Contact Closure
Trigger Input.
Power Supply- The DSP module is normally provided power through its DataPort connection from the amplifier. If you are
using an older amplifier or an amplifier that does not have a DataPort, an external power jack is provided on the DSP module.
If external power is required, use QSC’s DPX-1 accessory power supply.
INSTALLATION- Unpacking and What Else You’ll Need
It is recommended that you keep the original packing material for reuse in the rare event that service be required for your DSP-4. If service
is required, and the original packing material is not available, insure that the DSP-4 is adequately protected for shipment (strong box of
appropriate size , sufficient packing material).
What is included in the carton:
DSP-4 Digital Signal Processor
#4-40 machine screw, 1.88” long
#8-32 machine screw, 0.312” long
Hardware Manual (this document)
Signal Manager Software CD disk
What else will I need?
1- 200 MHz. Pentium PC (minimum) with CD-ROM, 32 MB or more RAM, 10 MB or more hard drive space available, an available COM (RS232) port capable of 38.4k baud, Windows 98, Windows 2000, Windows XP, or NT4.0 with service pack 6a or later, SVGA display at 800
x 600 minimum resolution (1024 x 768 recommended).
2- An RS-232 cable (9-pin serial data cable). This cable attaches your PC to the DSP module. It should be a male-to-female type and no longer
than 25 feet.
Other accessories that may be required (depending on application)DPX-2 DataPort Cable
(module to amplifier)- This
cable is a 6 foot long male-female
DataPort cable used for connecting the DSP-4 module to a
DataPort equipped amplifier.
DPC-X DataPort Cable
(module to CM16a)- This cable
is a custom length male-male
DataPort cable used for connecting
the DSP-4 module to a QSC
amplifier network monitor, such as
the CM16a. Length can be
specified from 1 to 10 feet, replace
“X” suffix with length in feet.
DPX-1 External Power SupplyThe DPX-1 is used in applications
where the amplifier’s DataPort
does not supply operating voltage
to the DSP-4 module. This includes
non-DataPort amplifiers and
certain models of QSC DataPort
equipped amplifiers (see Appendix
for details).
DPX-4 Mounting BracketThe DPX-4 holds up to 4 DSP-4 (or
DSP-3) modules in a highlyadjustable 19-inch rackmount
configuration. Main bracket comes
with right angle module support
brackets and adjustable rack
mounting ears for optimum
INSTALLATION- Software Installation
In order to use your DSP-4 module, you will need to install the QSC Audio Signal Manager software on your PC. The
module is configured to pass full range audio unattenuated from input-to-output as shipped from the factory. You must
use the software to configure the module as desired.
Software Installation1. Insert the CD labeled QSC Signal Manager into your CD drive (typically drive “D:”). If your
computer has AUTORUN enabled, the installation utility will start automatically. If it does not,
then proceed to step 2, below. Otherwise, proceed to step 3.
2. Run D:\Setup.exe (replace “D” with your CD drive’s designation if necessary) and follow the
instructions displayed.
3. When the installation is complete, you will be presented with a screen that prompts you
to view the “Readme” file. Please take time to read this- it contains important information on
how to use the software.
4. After installation, you will have an icon on your desktop labeled “Signal Manager”. Use this
icon to start the application.
5. Using the main menu bar at the top of the window, choose the “Help” item and read the
software help section. The Help system includes the most up-to-date information for
“paperless” reference. Also, visit QSC on the internet at http://www.qscaudio.com for
DSP-4 updates.
6. IMPORTANT! The DSP-4 is shipped with all of its presets configured to pass full-range
audio signals through both channels. THIS MAY NOT BE APPROPRIATE FOR YOUR
SETUP! Be sure to configure any necessary crossovers , filters, etc. prior to applying
audio signals to the inputs. Damage to equipment may result if these recommendations are not followed.
After the software has been installed and the DSP-4 module has been properly mounted and connected to the amplifier,
connect the RS-232 cable from your PC’s COM port to the DSP-4 module’s RS-232 connector. Then apply power to the
DSP-4 (turn on the amplifier or plug in the accessory external power supply). Turn on your PC and start the Signal
Manager software by clicking (or double clicking) on its icon. Refer to the software’s Help system for instructions on
creating and applying configurations to the DSP-4.
Do not run your amplifier “wide open” (maximum gain) while making real-time
adjustments to the DSP-4’s setup. The nature of the communication path between
the PC and DSP-4 is inherently more complex than direct physical controls of an
equivalent analog processing device. Unpredictable results may occur due to failure of the
PC or the communications port. Under such circumstances, damage to your speakers is
possible if the amplifier gain is set for high power levels. Use the minimum useful gain
settings while making system adjustments.
INSTALLATION- Mounting on Amplifier (QSC CX, DCA, Powerlight2)
The DSP-4 module mounts directly to the rear of QSC’s 2-channel, 2RU, DataPort equipped amplifiers. All
other models require the module to be mounted on an accessory bracket (refer to next page).
If you have an amplifier that supports “direct” mounting, you need to:
1- Configure the amplifier:
•All filters off
•Clip limiter setting does not matter
•Mode set as required (stereo, bridge mono, parallel)
2- Align the DataPort plug on the back of the DSP-4 with the DataPort jack on the back of the
amplifier and gently push the module to seat the connector.
3- Install the two #4-40 screws to secure the left side of the module to the amplifier. These
two long screws pass through the module and thread into the inserts on the DataPort (HD15)
jack. (see below). Use a #1-size phillips driver; be sure not to overtighten.
4- Install the #8-32 screw (0.312 inch long) to secure the right side of the DSP-4 to the amplifier
(see below).
Be sure to secure the DSP-4
using all three mounting
screws. The “backside”
DataPort connector can be
easily damaged if the module is twisted and there are
no supporting screws to
properly secure it to the
INSTALLATION- Remote mounting (4-ch., 8-ch. Powerlight & non QSC amp’s)
The DSP-4 module requires “remote” mounting when used with the 4- and 8-channel CX, 4-channel DCA,
Powerlight, and non-QSC amplifiers.
If you have an amplifier that requires “remote” mounting, you need to:
1- Obtain the Accessory Remote Mounting Bracket.
2- Attach the right angle bracket to the module (see illustration, below).
3- Mount the module/bracket assembly on the main bracket.
4- Secure the adjustable rack ears (included in bracket kit) to the main bracket.
5- Mount the completed assembly in your equipment rack.
6- Connect inputs, outputs, DataPorts, and external power as required.
Be sure to secure the DSP-4 using all mounting
Powerlight 6.0 and Powerlight 9.0 ampli-
screws. This will ensure reliable mechanical
fiers require that pin #9 be removed from
and electrical performance.
the remote mounting interconnect cable.
Amplifier damage may result from use of
cable that has pin #9 connections
INSTALLATION- DataPort Connections
When using the DSP-4 module with QSC’s amplifier network monitors, the audio input to the module can be delivered
through the DataPort along with amplifier control and monitoring signals. This is the normal application of the DataPort.
Connection from the module to the amplifier network monitor is made using a DPC-X male-male QSC DataPort cable.
Alternatively, the DataPort connection can be used ONLY for control and monitoring, while the audio is input via the XLR
inputs. If using the DSP-4 in this manner, do not apply audio via the DataPort as it will be mixed with the XLR audio input
The DSP-4’s DataPort output (rear panel DataPort) connects directly to QSC’s 2-channel, 2RU, DataPort equipped
amplifiers when mounting the module on the rear of the amplifier. For all other QSC DataPort equipped amplifiers, the
module is mounted on an accessory bracket and module-to-amplifier connection is made with a DPX-2 male-female
QSC DataPort cable. These connections are shown on the previous page.
If you are using the DataPort for audio input and/or control and monitoring, you need to:
1- Orient the DataPort connector with the DataPort jack.
2- Firmly insert the connector into the jack.
3- Tighten the connector’s retaining screws to ensure proper contact is made. Do not overtighten.
Do not use computer VGA cables as they are not correctly constructed for use with the DSP-4.
QSC DataPort cables may be obtained through your QSC distributor or by calling QSC’s Technical Services Department.
The DSP-4 can be used with non-DataPort equipment by utilizing the XLR connections. The accessory power
supply, DPX-1, is required for all non-DataPort applications.
Inputs- The audio input can be from one of two sources; the front-panel DataPort or the XLR input connectors. Do not use both sets of
inputs at the same time! Inputs are electronically balanced with an impedance of 8.3k ohms (balanced) or 3.7k ohms (unbalanced).
Input sensitivity is software-selectable from 1.5 to 18 volts (rms) full-scale. Shield terminals connect to the chassis. Use balanced
connections for the lowest possible noise levels and to minimize the possibility of hum-inducing ground loops.
Outputs- The DSP-4’s post-processor audio is output to the rear-panel DataPort AND the XLR output connectors. The outputs are
electronically balanced with an impedance of 600 ohms. Output level is software-selectable from 4 or 6 Vrms. The XLR out’s can
be used for daisy-chaining the processed audio to additional amplifiers, even when connected to a DataPort-equipped amplifier
via the rear-panel DataPort. The maximum number of QSC amplifiers that can be connected to the DSP-4’s outputs (including the
output DataPort) is five. This ensures THD stays below 0.1%. The effect on output level signal strength is about -3 dB when five
QSC amplifiers are daisy chained. An additional +12 dB of output gain is available in software (OUT1 and OUT2 blocks).
If making your own
cables, please refer to
proper pinout of the
Pinouts are provided
for balanced and unbalanced configurations.
INSTALLATION- RS-232 Connection
RS-232 connection to the DSP-4 module is required for “setting up” a configuration. After being setup and the
proper operation verified, the RS-232 connection is no longer needed. However, for “real time” adjustments,
the RS-232 connection to the computer must be maintained.
RS-232 PORT Connection1- Plug the 9-pin serial cable into the connector labeled RS-232 . Cable length should be 25 feet
or less. Orient the DB-9 plug correctly, insert the plug fully into the RS-232 port and finger-tighten
the retaining screws.
2- Plug the other end of the serial cable into an available COM port on your PC. Tighten the
retaining screws.
DSP-4 setup and programming takes place via the RS-232 port. Any time setup changes are required to the DSP-4, it must be connected
to its host computer through the RS-232 port. If “real-time” control of the DSP-4 is required, the RS-232 port connection must be maintained.
If “real-time” control is not required, then the DSP-4 can be setup first and then disconnected from the PC.
The RS-232 connection does not have to be maintained for the DSP-4 to operate.
Setup & programming can also be done via Ethernet network communication when using QSC’s QSControl products. Refer
to QSControl documentation for detailed information.
INSTALLATION- DPX-1 Accessory Power Supply
Connection to accessory external power supply (DPX-1)
When the module is used with QSC amplifiers that do not provide +15 VDC through their DataPort connection
OR is used with non-DataPort amplifiers, power must be supplied to the DSP-4 from an external power supply.
All non-QSC amplifier applications require use of the DPX-1 accessory external supply. Contact QSC’s
Technical Services Department or your QSC representative for more information. Any damage to the DSP4 caused by connection to a non-QSC external power supply is not covered under the warranty. Use of the
DPX-1 with QSC amplifiers that do provide +15VDC through the DataPort will not harm the DSP-4, although
it is not necessary.
When using the external power source, we recommend that the
DSP-4 be powered-up before the amplifier in order to insure troublefree start-up. This will avoid audio “thumps & bumps”.
Connection to an improper voltage source can cause immediate
damage to the DSP-4!
QSC offers the DPX-1 accessory
external power supply for applications with non-QSC amplifiers or with
QSC Powerlight models that do not
provide the required operating
To connect the DPX-1 to the DSP-4
module, plug the DPX-1 power
connecter into the DSP-4’s External
Power jack. Then plug the DPX-1
into the AC outlet. After the DSP-4
module has been powered up, the
amplifier may be turned on.
INSTALLATION- Daisy Chaining
Daisy chaining the DSP-4 outputs to additional amplifiers
The DSP-4 has two XLR audio outputs, one for each channel. These outputs may be used for daisy-chaining
the post-DSP signal to other amplifiers or for monitoring purposes. The XLR outputs may be used for daisychaining even when the DataPorts are used for input/output. Do not use Output Power Limiting when
daisy chaining.
To daisy-chain the DSP output, connect the output jacks of the DSP-4 to the input jacks of the
next amplifier. Then connect the paralleled signal from the first amplifier to the second amplifier, and so
on, up to a maximum of five amplifiers (including the output DataPort if connected to an amplifier). Make sure
that all interconnecting cables are balanced and connected properly.
USE- General Guidelines for Freely Configurable DSP
The DSP-4 is configured (programmed) by using the included Signal Manager software. The software must be installed
on your PC and the PC must be connected to the DSP-4 using a 9-pin serial cable and an available COM port. Once
programmed, the module can operate without any connection to the computer. Any time changes are needed to the
DSP’s configuration, the RS-232 connection must be active (cable connected). Software operating instructions are
provided in the form of an in-depth Help file in the Signal Manager software.
IMPORTANT! Please read before operating the DSP-4 with your audio system.
The DSP-4 is a professional level DSP product that allows the user to produce virtually unlimited signal
processor variations and configurations. Because of the infinite configuration possibilities of digital signal
processing and the DSP-4, it is possible to create configurations that may result in unwanted signals or
uncontrollable output
Signal Manager has no way of knowing if the DSP configuration you have designed will produce the results
you intend. You can create signal loops in your configuration that may oscillate and could damage your
sound system if you apply such configurations to the DSP-4. When applying an untested configuration or
when designing or experimenting with the DSP-4, it is a very good idea to turn down the amplifier’s physical
gain controls. That way, you won’t damage your speakers or create very loud sounds if you apply a
configuration that doesn’t do what you thought it would.
As a general rule, DO NOT CREATE SIGNAL LOOPS! Do not mix the output of a DSP object back into its
own input! There is nothing useful to achieve by doing that, you will only create an oscillator that could
These objects produce signals that can harm your speakers. Turn down the gain. If you don’t hear a signal
when you think you should, DO NOT INCREASE THE GAIN!!! If the signal isn’t audible at lower levels, there
is something else wrong. Turning up the gain to full exposes you and your system to the possibility that
some loose connection somewhere will suddenly send a full-amplitude signal through your sound system.
Like all freely configurable signal processing tools, the DSP-4 will do what the configuration you design
tells it to do. This may not be what you expect it to do, so use caution.
Special Information About Saving DSP-4 Configurations
The computer which is used to create the DSP-4 signal flow configurations, and subsequently
save them to disk, should be the same computer used to modify and adjust the DSP-4 settings
in the future. Naturally, this might not always be the case. At the least, a copy of the DSP-4
configuration(s) should be saved to floppy disk, so the configuration files can be transferred to
whatever computer(s) might be used to adjust or modify the DSP-4 module settings in the future.
The reason:
The Signal Manager software works in conjunction with the DSP-4 module to create specific signal processing algorithms for filters, delays,
limiters, and the like. The algorithms are displayed on the computer screen as ”configuration files”, with graphical representations of each
function and parameters. The user creates a signal chain, “wiring” together blocks of functions as needed for each particular audio channel
or channels.
USE- Special Information About Saving DSP-4 Configurations
Special Information About Saving DSP-4 Configurations (continued)
When you build a DSP-4 configuration from scratch (or load one from disk) and perform an “Apply to DSP” operation, the information
downloaded into the DSP-4 module is NOT the graphical representation of what is displayed on the screen. The downloaded information
consists of the compiled algorithm coefficients of the functions, i.e. “just the math”. If building a new configuration from scratch, when you
apply it to the DSP-4 you will also be prompted to save it to disk as a Configuration file (*.cfg). The path for this Configuration file is then
associated with the compiled information that is applied to the DSP-4. A previously saved (to disk) configuration file may also be applied
to the DSP-4, and that particular file path is associated with the algorithms now loaded in the DSP-4.
When you connect a DSP-4 to a computer, the Signal Manager software first attempts to locate and display the configuration file that has
been associated with the algorithm coefficients currently running in the DSP-4, to correlate “what you hear” with “what you see”. This would
allow you to further adjust a delay or a filter parameter, for instance. If the correct file is located, based on the associated path name, the
graphical configuration is displayed. If the file is not found (the file has been renamed, moved, deleted, or you are not using the same
computer on which the DSP-4 was originally configured) the computer will display a message asking if you would like to browse for a
Answering YES will open the Browse window. Once a configuration is selected, it is displayed on the screen, but not applied to the DSP4. Answering NO will merely display a blank workspace to the screen with no configuration loaded. At this point, what is displayed is NOT
what is currently running in the DSP-4 memory.
When the proper configuration file is displayed on the screen, go to the Configuration->Edit menu (Ctrl-E), followed by an Apply to DSP
command (Ctrl-D). This will download the currently displayed configuration back into the DSP-4 (overwriting itself), allowing synchronization
of what is displayed with what is running in the DSP-4. At this point, you may adjust parameters or modify settings as usual.
Overall Notes and Warnings
• The last applied configuration that is “running” in the DSP-4 when it is turned off becomes the active
configuration once the power is reapplied on to the DSP-4. This ensures that the system “comes up” just
as it was left the last time it was powered down.
• Do not run your amplifier “wide open” (maximum gain) while making real-time adjustments to the DSP4’s setup. The nature of the communication path between the PC and DSP-4 is inherently more complex than
direct physical controls of an equivalent analog processing device. Unpredictable results may occur due
to failure of the PC or the communications channel. Under such circumstances, damage to your speakers
is possible if the amplifier gain is set for high power levels. Use the minimum useful gain settings while
making system adjustments.
Audio converters
24-bit resolution, 48 kHz sampling rate
Frequency response at 3 dB below full scale input voltage
20 Hz–10 kHz ±0.3 dB (XLR outputs)
20 Hz–20 kHz ±0.7 dB (XLR outputs)
20 Hz–20 kHz±0.2 dB (DataPort outputs)
<0.01% typical THD+N @ +4 dBu out, 20 Hz–20 kHz
Delay (throughput)
1.5 millisecond
Dynamic range
>104dB min., unweighted, 1.5V input sensitivity
>106dB min., unweighted, all other input sensitivities
>107dB min., A-weighted, 1.5V input sensitivity
>109dB min., A-weighted, all other input sensitivities
better than 62dB down, 20 Hz–20 kHz, all sensitivities
better than 85dB down, 1 kHz bandpass, all sensitivities
Common-mode Rejection
50dB min.
In-phase or inverted
>90 dB attenuation
Program inputs
2 via XLR female or DataPort
Electronically balanced
All shield terminals connected to chassis
Input sensitivity
1.5, 4.0, 9.0 or 18.0 Vrms (full scale input level)
6, 14.5, 21.5 or 27.5 dBu
3.5, 12.0, 19.0 or 25.0 dBv
8.6 K Ohm balanced input
4.3 K Ohm unbalanced input
Program Outputs
2 via XLR male or DataPort
Pseudo balanced
All shield terminals connected to chassis
Outpu Level, pad* out (pad in)
6 (4) Vrms , full scale input level
*pad is software selectable
18 (14.5) dBu
15.5 (12) dBv
600 ohms typical
Note: Specifications are subject to change without notice.
all professional audio power amplifiers
Full Feature Set
all QSC DataPort-connected amplifiers (“V2” DataPort reduced set)
Features Supported by QSC DataPort Amps
channel CLIP sensing, PROTECT status, active Power Limiting
DataPort Connector & Cable (if using)
proprietary pinout HD-15 connector, 1 female “input” DataPort and
1 male “output” DataPort. Cables are of proprietary construction
and are available from QSC’s Technical Services Department. No
“output” cable required for QSC amps that support direct mounting.
Amplifiers per DSP-4
1 two-channel amplifier per DSP-4
RS-232 port is used for “downloading” DSP configurations into the
DSP-4 from your PC.
Cable Type
Normal 9-pin serial data cable, male-to-female, 25 feet maximum
1 discrete input (pin #9 of RS-232 port), TTL compatible
single ended input
Resistance for closure detect
<800 Ohms
Resistance for open detect
>3.2 K Ohms
Maximum voltage input
Height, Width, Depth
3.50 x 3.75 x 2.05 inches
0.9 lbs. (0.41 kg)
direct mount to QSC 2RU, DataPort amplifiers
remote mount to other amplifiers
Operating Temperature Range
0° to 50° C.
Note: Specifications are subject to change without notice.
Architect’s and Engineer’s Specifications
The Digital Signal Processor (DSP) shall provide two independent
channels of DSP for signal delivery to QSC DataPort equipped
power amplifiers. The processing shall be distributed with the DSP
module mounted directly to the rear of the power amplifiers.
Output Power Limiter—For each audio channel, the DSP shall
provide a power limiter that is assignable anywhere in the
signal chain and can be switched on or off. The limiter shall
Contact Closure I/O—The DSP shall provide a trigger input
usable for contact-closure (or other) purpose which shall
be CMOS & TTL signal compatible.
Delay— The DSP shall multiple delays with a total available delay
time of at least 910 milliseconds.
Power Supply—The DSP shall be provided power through its
DataPort connection to most QSC DataPort equipped
amplifiers. For older amplifiers and non-QSC amplifiers,
a coaxial power jack will be provided on the DSP for
connection to an external power source. Power required
Attack time
shall be +15 VDC at 300 mA (max.).
provide the following adjustments:
Release time
Amplifier Interface—The DSP shall attach directly to the rear of
Butterworth (6,12,18,24 dB per octave slope)
each power amplifier. The DSP’s interface to each power
amplifier shall be via an HD-15 connector (DataPort).
This interface shall transmit two amplifier input audio
signals as well as all control and monitoring signals.
Special signal conditioning and grounding techniques
shall be used in this interface to ensure negligible levels
of noise and crosstalk. For non-DataPort amplifiers, there
shall be mounting and interface options provided for
Bessel (6,12,18,24 dB per octave slope)
operating with the DSP.
High- and Low-Pass Crossovers—For each channel of audio,
the DSP will provide high-pass and low-pass crossovers
that are assignable anywhere in the audio chain. The
crossovers must be capable of being switched in or out
of the signal chain. The DSP shall provide the following
crossover responses:
Linkwitz-Riley (12 & 24 dB per octave slope)
High- and Low-Pass Shelf Filters—For each audio channel, the
DSP shall provide high-pass and low-pass shelf filters
that are assignable anywhere in the audio chain. The
shelf filters must be capable of being switched in or out
of the signal chain. The DSP shall provide the following
shelf filter adjustments:
Amplifier Output Monitoring—When used with QSC DataPort
amplifiers, the DSP shall provide clipping and protect
status detection at the amplifier’s output terminals.
Noise & Tone Generation-- The DSP shall provide pink and
white noise generation capability. It shall also provide for
tone generation.
Presets— The DSP shall be capable of storing at least 8 preset
Variable corner frequency
configurations. The control software shall provide man-
Variable gain
agement of these presets.
Variable slope
Compressor— The DSP shall provide a signal compressor that is
assignable anywhere in the signal chain. It shall have adjustable
threshold, attack time, release time, and compression ratio.
Mixer— The DSP shall provide multiple 2-to-1 mixers.
Polarity— The DSP shall provide for polarity reversal.
General—All audio inputs and outputs shall be balanced with a
nominal input level of +4 dBu and maximum level of +21
dBu. Input and output Gain controls shall be provided.
Input and post-processor output connectors shall be
Control— The DSP shall be configurable via RS-232 or via a
networked DataPort connection.
The Digital Signal Processor shall be the QSC DSP-4.
APPENDIX- DataPort Pinout
The diagram below shows the pin assignments used for the HD-15 connectors on
the DSP-4 and amplifier.
Signal Description
Ch. 1 Minus (-) Input Signal
This information is shown for reference
AC Standby Control
only and is subject to change without no-
V- MON Ch. 1 and Encode 1
tice as the DataPort feature is specific to
I- MON Ch. 1 and Encode 2
QSC products and not intended for inter-
Clip/Protect Ch. 1
face to other manufacturer’s equipment.
Hard Ground
Ch. 1 Plus (+) Input Signal
Ch. 2 Plus (+) Input Signal
+15V from Amplifier
Data Reference Ground
Ch. 2 Minus (-) Input Signal
Amplifier IDR (Model ID)
V- MON Ch. 2 and Encode 3
I- MON Ch. 2 and Encode 4
Clip/Protect Ch. 2
Note: Powerlight 6.0 and Powerlight 9.0 amplifiers
require that pin #9 be removed from the remote mounting
interconnect cable (DPX-2).
Amplifier damage may result from use of cable that has
pin #9 connections present.
Description of Encode Signals
encode 1
Bridge mode & power detect
encode 2
Temperature, channel 1
encode 3
encode 4
Standby mode detect
Temperature, channel 2
APPENDIX- RS-232 Port Pinout & Connector P-N’s
RS-232 PINOUT: The diagram below shows the pin assignments for the RS-232 connector on the DSP-4.
Note that Pin #9 is used for Contact Closure function (normally not used in RS-232).
Signal Description
Signal GND
contact closure
Balanced connection is recommended for all inputs. The
XLR input pinout
XLR inputs on the DSP-4 are electronically balanced. Balanced
input cables are recommended to minimize noise pick up and
pin 2
pin 3
prevent ground loops.
pin 1
If constructing your own cables, refer to the pinout, above, for
proper connector wiring.
Unbalanced inputs can be used if required. If unbalanced
Jumper pin 1 to 3
XLR input pinout
audio sources are used, the minus (-) and shield terminals should
be connected with a jumper wire.
However, it is preferable to use an audio transformer (or other
unbalanced-to-balanced “converter”) to provide a balanced input
to the DSP-4.
pin 2
jumper pin1 to pin 3
pin 1
APPENDIX- Application Information
As design improvements are continuous, the following information is subject to change. Contact QSC for current information.
QSC’s DSP-4 Module has been designed to attach directly to the DataPort connector of QSC’s CX, DCA, and Powerlight 2 series
amplifiers. When attached to CX, DCA, and Powerlight 2 amps manufactured 08/99 and later, the module receives its power
through the DataPort from the amplifier. Modules connected to earlier models of those just mentioned and all Powerlight
amplifiers (the “non-2’s”) require an external DC supply (available from QSC).
TO CLARIFY: CX, DCA, and PL2 amps made prior to August 1999 DO NOT provide adequate power supply voltage to
the module, requiring the use of the same type of external DC supply as used with Powerlight amplifiers. The amps in
question will have a serial number PRIOR to 0899XXXXX, where the first four digits of the serial number are the MMYY datecode.
Again, the modules WILL work with these amps, but will require the use of our external power supply.
•Full feature set, Direct-mounting, No external power required, No special interconnect cables required for the
following QSC power amplifiers with serial numbers of 0899XXXXX and later, where the first four digits of the serial number are the MMYY
datecode :
CX series:
DCA series:
PL2 series:
PL2A series:
CX302 - CX1202V (all)
DCA1222, DCA1622, DCA2422, DCA3022, DCA342
PL224, PL230, PL236, PL218
•Remote Mounting Required, QSC DataPort Cable required: Full feature-set, no external power required.
CX series:
DCA series:
CX204V, CX254, CX404, CX168
DCA1644, DCA1824
•Remote Mounting, QSC DataPort Cable and External Power required: Full feature-set.
Powerlight series:
PL1.0 through PL4.0 (all)
PL6.0 and PL9.0 require modified DataPort cable between DSP-4 and amplifier.
Powerlight 6.0 and 9.0 MUST have
pin #9 removed from the Amplifierto-DSP DataPort Cable (DPX-2) before use!
•Remote Mounting and External Power required. No DataPort Connection possible, Power Limiting not available.
ISA series:
The ISA amplifiers have a “V2” DataPort that may be used for audio inputs only.
MX series:
PLX series:
RMX series
USA series:
ALL non-QSC amplifiers can be used with the DSP-4
Section 7: Maintenance, Warranty & QSC Contact Information
The faceplate and chassis can be cleaned with a soft cloth and
QSC Audio Products, Inc. is not liable for any damage to speakers,
nonabrasive, mild cleaning solution. Products like Simple Green
amplifiers, or any other equipment that is caused by negligence or
and Windex work well. Do not use powders or scrubbing pads of any
improper installation and/or use of the DSP-4 digital signal proces-
type as they are usually abrasive and will permanently damage the
sor. Due to the inherent complexity of the communications between
finish of your DSP-4. Dampen a soft, lint-free cloth with the
the DSP-4 and the host computer, QSC Audio Products, Inc. is not
cleaning solution and wipe the DSP-4 down gently. Insure that
liable for any direct or indirect damage caused by computer commu-
cleaning solution does not get down into the connectors. Do not
nications failure.
spray the solution directly onto the DSP-4 as it will penetrate into
Product Warranty
the connectors.
QSC Audio Products, Inc. (“QSC”) guarantees its products to be
User Maintenance
free from defective material and / or workmanship for a period of
There is no user-level maintenance on the DSP-4. Contact QSC’s
three (3) years from date of sale, and will replace defective parts
Technical Services Department if service is required.
and repair malfunctioning products under this warranty when the
Warranty Information
defect occurs under normal installation and use - provided the unit
is returned to our factory or one of our authorized service stations
If the DSP-4 isn’t working properly, please verify that a
known good 9-pin serial cable is used between the DSP-4
and the computer. If proper operation can not be restored,
the DSP-4 may require service. This must be performed by
qualified service personnel. To obtain the location of your
nearest QSC Authorized Service Center, please contact
your QSC dealer or contact QSC’s Technical Services
via prepaid transportation with a copy of proof of purchase (i.e.,
sales receipt). This warranty provides that the examination of the
return product must indicate, in our judgment, a manufacturing
defect. This warranty does not extend to any product which has
been subjected to misuse, neglect, accident, improper installation,
or where the date code has been removed or defaced. QSC shall
not be liable for incidental and/or consequential damages. This
warranty gives you specific legal rights, and you may also have
other rights which vary from state to state. This limited warranty
is freely transferable during the term of the warranty period.
If the DSP-4 is returned to the factory for service, it should be sent
in the proper QSC carton. If you did not save the original carton, ask
Main Number
(714) 754-6175
Sales Direct Line (714) 957-7100
your QSC dealer for one or call QSC to have one sent to you. This
warranty does not cover shipping damage caused by improper
packing or the use of improper shipping cartons.
or (800) 854-4079 toll free (U.S.A. only)
Technical Services (714) 957-7150
or (800) 772-2834 toll free (U.S.A. only)
QSC Audio Products, Inc.
1675 MacArthur Boulevard
Sales & Marketing FAX
(714) 754-6174
Technical Services FAX
(714) 754-6173
Costa Mesa, CA 92626-1468 USA
1675 MacArthur Boulevard
Costa Mesa, California 92626 USA
PH: (714) 754-6175 FAX: (714) 754-6174
© Copyright 2002, QSC Audio Products, Inc.
QSC® is a registered trademark of QSC Audio Products, Inc., Costa Mesa, CA
“QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office
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