CX168
8-Channel Installed Sound
Professional Audio Amplifier
User Manual
*TD-000095-00*
TD-000095-00 rev.A
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TABLE OF CONTENTS
INTRODUCTION:
CX168 Overview .......................................................................................4
Front Panel Illustration .........................................................................................4
Rear Panel Illustration ........................................................................................5
Mounting Dimensions .........................................................................5
INSTALLATION:
What is Included..............................................................................................6
Rack Mounting ....................................................................................6
Supporting the Rear of the Amplifier.....................................................6
Fan Cooling...........................................................................................7
AC Mains (AC Power) Connection..............................................................................7
SETUP:
Setting the Configuration (MODE) Switches....................................................8
Setting Operating Mode (Stereo, Parallel, or Bridge)........................................9
Clip Limiter Setting.............................................................................10
Low Frequency (Subaudio) Filter Settings................................................................10
Low Frequency Filtering Tips and CX168 Frequency Response Curve...................11
CONNECTIONS:
Inputs: Connecting to the Input Terminal Block Inputs ...................................12
Connecting to the DataPort Inputs.......................................................13
Outputs: Connecting the Outputs in Stereo or in Bridge Mode .........................14
How to use the 8-pin Output Connectors................................15
OPERATION:
Power Switch ............................................................................................16
LED Indicators .......................................................................................17
Gain Controls ......................................................................................18
Security Plate for Gain Controls .........................................................19
DataPort Connector ...................................................................................20
DataPort Guidelines for the CX168.........................................21
APPLICATIONS:
Four Room, Stereo Feed..............................................................................................22
Tri-Amplified, Stereo Cabinets with Subwoofer..............................................22
APPENDIX:
Detailed Explanation of Stereo, Parallel, and Bridge Operating Modes..........24
Multiple Speaker Loads in Series........................................................26
Multiple Speaker Loads in Parallel........................................................27
TROUBLESHOOTING ........................................................................................................28
SPECIFICATIONS ......................................................................................................30
WARRANTY INFORMATION .............................................................................................32
HOW TO CONTACT QSC AUDIO PRODUCTS ............................................................................32
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INTRODUCTION
Congratulations on your purchase of the CX168 power
amplifier. To help you obtain the best results from your
purchase, we encourage you to carefully review this manual.
With information including connections, configuration and
operation, it offers many useful guidelines.
Alternatively, these DataPorts facilitate connection of signal
processing equipment, such as QSC’s DSP-3, which offers two
channels of independent digital signal processing - including
crossover filters, shelf filters, signal delay, compression, peak
limiting, and parametric filters.
The CX168 provides a high level of channel density in a small,
lightweight form factor ideal for multi-zone audio systems.
Representing the culmination of QSC’s extensive experience
in power amplifier development, the CX168 is a highly
versatile, reliable, and user-friendly tool that will likely remain
a central component of your system for years to come.
As individual channel pairs may be bridged, the CX168 is
configurable as a 4-, 5-, 6-, 7-, or 8-channel unit. Further, the
CX168 features detachable Phoenix-style input and output
connectors—enabling the audio system to be wired with
greater ease. Other features include 1-dB recessed and
detented gain controls and a security cover for tamper-proof
installations.
Like the entire CX Series, the CX168 is equipped with QSC’s
exclusive PowerWaveTM switching power supply technology
to virtually eliminate noise and hum while reducing the unit’s
overall weight. Comprehensive protection circuitry includes
DC, infrasonic, thermal overload and short circuit protection.
The CX168 is easy to use. All operating mode switches are
grouped together on the rear panel, with one switchblock per
channel pair. These switches enable clip limiter on/off, LF
filter on/off, LF filter select and operation modes. The
amplifier’s front panel includes corresponding LEDs to indicate
Bridged or Parallel modes in addition to Signal and Clip
status.
The CX168 includes 4 HD15 DataPorts (one per channel pair)
for remote management or DSP. These ports allow each
channel pair to be governed by QSControl, QSC’s audio
networking system—enabling the system operator to control
amplifier gain levels, check the unit’s clipping and thermal
status, plus monitor numerous additional system parameters.
Your CX168 power amplifier was designed to provide many
years of trouble-free, great-sounding operation. We hope you
enjoy your new CX168.
FRONT PANEL
FRONT PANEL WITH
SECURITY PLATE
4
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INTRODUCTION
REAR PANEL
DIMENSIONS
AND MOUNTING
POINTS
5
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INSTALLATION: UNPACKING & RACK MOUNTING
What is Included
Save the container and packing material
so the amplifier may be shipped without
damage if service is ever required. If the
original container is not available, be
Your CX168 shipping container, as shipped from the factory,
includes:
sure to use a strong shipping container with enough
packing material to prevent the amplifier from being
damaged in transit.
- CX168 eight channel audio power amplifier
- this user’s manual
- security cover (plate) for gain controls
- self-adhesive rubber feet (use for non-rack mount applications)
- eight 3-pin terminal block input connectors
- two 8-pin terminal block output connectors
- #14AWG IEC-type detachable power cord
Rack Mounting
Use four screws and washers to secure the amplifier to the
equipment rack rails. Support the weight of the amplifier
while securing it to the rails to avoid bending or distorting
the mounting ears. The amplifier may be used in an
equipment rack or as a stand-alone unit. Rack mounting is
optional. Self-adhesive rubber feet are provided for non-rack
mount applications.
Supporting the Rear of the Amplifier
Unless the amplifier is being installed in its final, fixed
location, we strongly recommend supporting the rear of the
amplifier.
Supporting the rear of the amplifier is required for mobile
and portable use. If the amplifier is to be transported in any
way, install the optional rear rack mounting ear kit to
support the rear of the amplifier. During transport, the shock
loads encountered on the chassis and rack can easily
damage an unsupported amplifier and the rack rails. With
proper support, reliability is enhanced.
Optional rear rack mounting ear attachment methods-
refer to the rear rack mounting ear kit’s documentation
for details
Rear rack mounting ear kits are an accessory item and are
available from QSC’s Technical Services Department or from
your dealer or distributor. Refer to the literature included
with the rack mounting ear kit for installation instructions.
Two methods of rear rack mounting ear attachment are
possible; use the method that best suits you application.
6
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INSTALLATION: COOLING & AC MAINS REQUIREMENTS
Fan Cooling
The CX168 amplifier draws cool air into the rear of the
amplifier and exhausts hot air from the front. This is done so
the equipment in the rack stays as cool as possible. This
method of cooling gives the operator “direct” air tempera-
ture feedback at the front of the rack, where it is the most
convenient. The front panel’s temperature indicates “how
hard” the amplifier is working.
The fan varies speed automatically to maintain safe internal
temperatures and minimize noise. Keep the front and rear
vents clear to allow full air flow.
Air flow in QSC amplifiers
Do not obstruct the front or rear air vents! Make sure that plenty of cool air can enter
the rack, especially if there are other units which exhaust hot air into it.
AC Mains Connection
The correct AC line voltage is shown on
the serial number label. Make sure the AC
mains is the correct voltage. Connecting to the
wrong line voltage is dangerous and may
damage the amplifier.
Connect the AC line cord by orienting the
IEC plug correctly and pushing the plug firmly
into the IEC receptacle. It should seat tightly. It
can only be inserted when it is properly
oriented.
Use the cord supplied with the amplifier, or an
equivalent. Insure that the wire gauge of the
cord is #14AWG. Use of #16 or #18 AWG can
be dangerous and is not recommended.
The correct AC line voltage is shown on the
serial number label.
Use the best possible connection to the
AC power source. Avoid extension cords as
they will cause some voltage drop between
the AC source and you amplifier. If the use of
an extension cord is required, ensure that it is
the shortest length possible and is at least
#14 AWG. Ensure that all grounding connec-
tions are maintained.
Connecting to the wrong line voltage is
dangerous and may damage the amplifier or
constitute the risk of electric shock. Verify the
correct AC line voltage by checking the
specification printed on the serial number
label on the rear panel.
NOTE: Excessive length or inadequate gauge
may result in short muting episodes if all
channels are driven to full power.
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SETUP: SETTING THE MODE CONFIGURATION DIP SWITCHES
Setup
By using the mode switches and connecting to the amplifier
properly, the CX168 amplifier can be configured as a 1 to 8
channel amplifier. This flexibility enables the CX168 to be
used for most any multichannel application.
The CX168 can be thought of as four separate 2-channel
amplifiers on one chassis. Each of the four amplifier
sections may be operated in Stereo, Parallel, or Bridge mode
independently of the others. For example, channels 1 & 2
could be set for stereo operation while channels 3 & 4 are
set for parallel operation; all while channels 5 & 6 and
channels 7 & 8 are set for bridge mode.
The channels are grouped as follows:
Channels 1 and 2
Channels 3 and 4
Channels 5 and 6
Channels 7 and 8
You can set the operating mode for each group by setting
that group’s configuration DIP switches in the desired
positions. It is NOT POSSIBLE to group the channels
differently. For instance, you can not bridge channels 3 & 5
“MODE” configuration DIP switches are located on
because they are not in the same channel group.
the rear panel and look like the illustration above.
Switch positions shown are for example only. Set
switches as required for your application.
Before setting the configuration DIP switches, you must first
decide how the amplifier will connect to the speaker
system.
“MODE” switch settings and speaker connection diagrams are printed on a rear panel label, as shown, above.
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SETUP: SETTING THE MODE: STEREO, PARALLEL, OR BRIDGE
Modes
The following descriptions apply to a channel pair (such as Ch. 1 & 2 or Ch. 7 & 8). It is possible to set each channel pair’s mode
differently and customize the system configuration. All possible combinations will not be shown. The following describes the
behavior of one channel pair in the three modes of operation and the BRDG and PAR LED’s:
Stereo- Stereo mode supports two completely
separate audio channels, usually referred to as ‘left’
and ‘right’. Stereo configurations have two separate
input signals and two separate output signals.
Mode switch settings and LED indication for stereo mode operation.
BRDG and PAR indicators should not be illuminated when in stereo mode.
Parallel- Parallel mode applies one input signal to
both channels. Both inputs of a channel pair are
connected in parallel when the mode switch is set
for parallel, therefore, connect only one input per
channel pair when in parallel mode. The outputs are
connected the same as stereo mode. Each speaker
will be supplied the same signal, which is still
controlled by that channel’s gain control.
Mode switch settings and LED indication for parallel mode operation.
PAR indicator should be illuminated and BRDG indicator should not be
illuminated when in parallel mode.
Bridge- Bridge mode combines the two channels of
a pair (such as Ch. 3 & Ch. 4) into one higher-
powered channel. Like parallel mode, both inputs of
a channel pair are connected in parallel when the
mode switch is set for parallel, therefore, connect
only one input per channel pair when in bridge
mode. There are 4 possible channel pairs that can
be bridged on the CX168. They are Ch.1-2 Bridge,
Ch. 3-4 Bridge, Ch. 5-6 Bridge, and Ch. 7-8 Bridge.
Any pair or number of pairs can be independently
configured in bridge mode. Use the first channel’s
Mode switch settings and LED indication for parallel mode operation.
BRDG indicator and PAR indicator should be illuminated when in bridge
mode.
input and gain control when in bridge mode. The
second channel’s gain control is non-operative and
should be turned all the way down.
Note! Do not connect more than one input per channel pair when operating in parallel or bridge mode. However,
in parallel or bridge mode, the unused input terminals may be used for daisy-chaining the input signal to other
channels of the CX168 or to other amplifiers.
For pictorial description of operating modes, see Appendix.
9
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SETUP: MODE SWITCHES: CLIP LIMITER AND LOW FREQUENCY FILTERS
Clip Limiter
The CX168 amplifier has separate clip limiters for each of
the 8 channels. These clip limiters respond only to actual
amplifier clipping. Amplifier clipping generates internal error
signals which cause the clip limiter to quickly reduce gain
and minimize the overdrive. To preserve as much of the
program dynamics as possible, limiting occurs only during
actual clipping. Each channel’s clip limiter can be switched
on or off individually.
The clip limiter is internally set to respond as fast as
possible after clipping is detected. For program material that
is primarily “full-range”, the effect on the overall audio
quality should be imperceptible. We recommend using the
clip limiters for almost all applications, especially full-range
audio applications. Clipping can cause high-frequency
artifacts to be output to the speakers, potentially damaging
fragile high-frequency drivers.
For program material that is primarily low-frequency in
nature (low-frequency or subwoofer drive) this may be
perceived as a “rubbery” effect on the audio. If this is the
case, it may be preferable to turn the clip limiters off and let
the amplifier clip occasionally. With robust, low-frequency
drivers, the occasional clipping should cause no problems.
CAUTION! Clip limiting reduces extreme
overdrive peaks, allowing a higher average
signal level without distortion. Increasing the
gain with the clip limiter engaged until
clipping is again audible, can double the
average output power. Be careful not to
exceed the power rating of the speakers!
Low Frequency Filter
When driving speakers with limited low frequency
response, it is important to limit the low frequency
response of the amplifier. Doing so can result in more
usable bass response since the speaker is not being
overloaded by very low frequencies it can’t handle.
Explanation- Low frequency sound waves require much
more speaker cone motion to produce the same apparent
loudness as higher frequencies. Properly designed speaker
enclosures help the speaker to move more air with less
motion using techniques like porting. Such enclosures only
benefit from porting down to a certain frequency. Below
this frequency, the speaker is “unloaded” and is basically
free to move around uncontrollably without producing much
bass. Limiting the frequency range of the low frequency
content enables the speaker to behave the way it was
designed to. If frequencies lower than designed are
supplied to the speaker, performance will degrade.
All low frequency filters will change the character of low
frequency transients. For best results, the cabinet design,
speaker capabilities, and program material must be taken
into account when configuring low frequency filtering.
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SETUP: MODE SWITCHES: CLIP LIMITER AND LOW FREQUENCY FILTERS
Low Frequency Filtering Tips:
•
•
•
•
•
•
The OFF position should be used only for subwoofer systems with rated frequency response below 33 Hz. or if low frequency
filtering is provided by other devices.
Know the specification of the speaker cabinet you are driving. Match the low frequency roll off setting to the specified low
frequency capability of the speaker cabinet. Do not drive the speaker with frequencies below its rating.
Unless you have low frequency filtering before the amplifier, use the low frequency filter to protect your loudspeakers from
cone over-excursion caused by frequencies below the speaker’s limits.
The 33 Hz. rolloff is a good “all purpose” setting. Turn the filter on by setting the appropriate DIP switch to ON position and
select 33 Hz. using its 33/70 Hz. DIP switch. This setting is a good starting point for most large, full-range cabinets.
The 70 Hz. rolloff is a good setting to use with smaller, compact speaker cabinets having limited bass capability. Turn the
filter ON and select the 70 Hz. setting when using smaller cabinets.
The frequency selection ( 33 or 70 Hertz) has no effect unless the filter is set to the ON position.
Frequency Response Curves
11
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CONNECTIONS: INPUTS- Using the Terminal Block Inputs
Each channel has an active balanced "Euro-style" terminal block
input jack. These terminal blocks allow the input wiring to be
terminated using simple hand tools and allows for quick
reconfiguration when needed. The input impedance is 20k ohm
balanced or 10k ohm unbalanced.
Balanced connection is recommended for all audio inputs.
Balanced signals are less prone to AC hum and other electrical
noise. Unbalanced signals can be suitable for short cable runs.
The signal source's output impedance should be less than 600
ohms to avoid high frequency loss in long cables.
If the DataPort is being used for the input signal source,
the terminal block connections should not be used for
inputs. However, they may be used for daisy chaining the
DataPort input signal to other channels or amplifiers. The signal
available from the terminal block input connections will be about
10 dB lower than the signal presented to the DataPort.
TERMINAL BLOCK
CONNECTORS
Terminal Block Connectors:
Balanced inputs: Connect the
conductors to the connector as
shown.
shield
Terminal block: balanced connections
Unbalanced inputs: Connect the
conductors to the connector as
shown. Make sure that the unused
side of the balanced input is
connected to ground, as shown.
jumper
shield
Terminal block: unbalanced connections
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CONNECTIONS: INPUTS- Using the DataPorts
If used, the DataPort must be connected to a QSC DataPort product
using a QSC DataPort cable. Do not use computer cables; they look
similar but can cause operational problems with your amplifier and/or
DataPort accessories.
DATAPORT
CONNECTORS
The CX168 amplifier is equipped with four QSC DataPort connections
that may be used for connecting to accessory QSC DataPort devices.
Each DataPort services a specific channel pair; the channels are paired
as:
Ch. 1 and Ch. 2
Ch. 3 and Ch. 4
Ch. 5 and Ch. 6
Ch. 7 and Ch. 8
Each DataPort and its associated terminal block input pair can be
configured independently (there is no requirement to use a DataPort
connection for all channels). Only the Ch.1-Ch.2 DataPort can control the
power supply standby mode.
The DataPort connection will supply the input signals to the amplifier. If
using the DataPort connection for audio input signals, do not apply
inputs to the terminal block input connectors. If the DataPort connection
is used only for monitoring amplifier operating conditions and NOT for
providing audio inputs to the amplifier, then the terminal block inputs
may be used to supply the audio inputs to the amplifier.
How to Connect to the DataPort:
Direct mounting of DataPort accessories is NOT supported by the CX168 amplifier. Devices
that are normally mounted directly to the amplifier must be mounted remotely and connected to the
DataPort using a DataPort cable. This is due to the high density of connectors on an eight-channel
amplifier; there is not enough space to allow for accessories to be mounted directly to the back of the
amplifier.
If the accessory attaches with a QSC DataPort cable, orient the HD-15 male plug correctly with
the DataPort socket on the amplifier (it is “D” shaped and will fit only one way). Push the plug onto the
socket firmly and ensure it is seated properly. Finger-tighten the 2 retaining screws. Do not over tighten.
Basic DataPort Notes:
1- The amplifier Gain controls will need to be set at their anticipated high-level setting. Use reduced level
setting during setup & test.
2- If using the DataPort for audio input signals, control of the audio level will be accomplished with the
DataPort accessory device to which the amp is connected.
3- Control of the amplifier’s AC power standby mode will only be possible via the Ch.1-2 DataPort. The
amplifier’s POWER switch must be physically set to the “ON” position to use the standby control feature.
4- The order in which the four DataPorts are connected to external devices makes no difference to the
amplifier. However, the host controller to which the amplifier is connected will show the channels in the
order that cables are connected.
13
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CONNECTIONS: OUTPUTS
Outputs
Refer to the label on the rear panel of the amplifier for proper wiring connections. The output connection for STEREO and
PARALLEL modes is on the left side of the label , while the output connection for BRIDGE mode is shown to the right side of
the label. Note: Polarity changes from channel to channel and is different for bridge mode. Be certain of polarity of connec-
tions before applying power. Reversed polarity may degrade audio frequency response.
Speaker connection diagrams and “MODE” switch settings are printed on a rear panel label, as shown, above.
Stereo and Parallel Mode
In stereo or parallel mode, each speaker is connected to its
own individual channel of the amplifier. This connection
method is shown on the left side of the connection diagram
(rear panel) or in the diagram, right.
Use 4 ohm minimum impedance in stereo or parallel
mode. Ensure the mode configuration switches are set for
stereo or parallel mode when connecting speakers to each
channel’s output.
Stereo or parallel connection- single speaker shown con-
nected to amplifier channel 6 output. Ensure that all speaker
connections maintain proper polarity ( + to +, - to - ).
Bridge Mode
In bridge mode, each speaker is connected to a bridged-pair of
outputs. The channels must first be “bridged” by setting the
mode configuration switches to the bridge settings. Then con-
nect the speakers as shown on the right side of the connection
diagram (rear panel) or in the diagram, right.
Use 8 ohm minimum impedance in bridged mode.
Ensure the mode configuration switches are set for bridge
mode when connecting speakers to bridged output pairs .
BRIDGE MODE PRECAUTIONS:
Do not use 2 ohm or 4 ohm loads in bridge mode! 8
ohms is the minimum impedance for bridge mode
operation. This mode puts a high demand on the
Bridge connection- single speaker shown connected to am-
plifier channels 5 and 6 (bridged with mode switch settings).
amplifier and speaker. Excessive clipping may cause
protective muting or speaker damage. Ensure the speaker has
a sufficient power rating.
Ensure that all speaker connections maintain proper polar-
ity ( + to +, - to - ).
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CONNECTIONS: OUTPUTS- USING THE TERMINAL BLOCK CONNECTORS
OUTPUT TERMINAL SAFETY WARNING!
Do not touch output terminals while amplifier power is on.
Make all connections with amplifier turned off. Risk of
hazardous energy!
When selecting speaker cable (wire), always use the
largest wire size and shortest length of wire practical for
an installation. Larger wire sizes and shorter lengths
minimize power loss and degradation of damping factor. Do
not place speaker cables next to input wiring.
Terminal Block Connections
The output connections are made by attaching speaker
wires to the 8-pin terminal block connectors. Once these
connectors have been “populated” with the necessary
speaker wire connections, plug the terminal blocks into
their respective output jack.
The output jacks are configured in two discrete connectors.
One connector carries the connections for channels 1
through 4. The other, channels 5 through 8. Each connector
has 8 pins, each of which connects to the speaker wire
using a screw-clamp. Refer to the diagram, right, for the
basic connection procedure. Be sure that speaker polarity is
maintained. The locations of the “+” and “-” terminals on
the amplifier is not the same for each channel.
Ensure that all wires are neatly terminated with no loose
strands. Do not strip the insulation back excessively. Loose
strands and exposed wire beyond the terminals may cause
a short circuit and cause protective muting of the amplifier.
Once all the required connections have been made to the
terminal block connectors, they may be inserted into the
OUTPUTS jack on the rear panel. Orient the connector
properly (it only fits one way) and push it in until it is fully
seated in the receptacle. Note each connector is oriented so
its wires face outwards.
How to make connections to the terminal block:
1- Strip the wires approximately 0.28” (7mm).
2- Twist any loose strands of wire together.
3- Loosen the appropriate retaining screw fully.
4- Insert the stripped wire into the receptacle.
5- Tighten the appropriate retaining screw to secure.
15
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OPERATION: POWER SWITCH and GAIN CONTROLS
Power Switch
The power switch is a rocker-type switch. It is located on
the left side of the front panel. To turn the amplifier on, push
in on the top of the switch. To turn the amplifier off, push in
on the bottom of the switch.
The green power LED should light up when the switch is in
the on position.
When the power is switched off, the LED may takes several
seconds to go out; this is normal.
To turn the amplifier ‘on’, push in on the top por-
tion of the rocker switch firmly. It should move
inward and snap into the ‘on’ position. After
switching on, the power LED should illuminate.
To turn the amplifier ‘off’, push in on the bottom
portion of the rocker switch firmly. It should move
inward and snap into the ‘off’ position. After
switching off, the power LED should extinguish.
If the POWER LED fails to illuminate when
the switch is in the ON position:
1- Check the AC cord and insure that both ends are fully
inserted into their receptacles. If the power LED still fails to
illuminate,
2- Check the AC outlet for voltage with a circuit tester or
known good device (lamp, etc.).
3- Make sure that the amplifier is not in STANDBY mode. If
the amplifier is being controlled by one of its DataPort
connectors, the amplifier may be in standby mode. Verify the
AC power status from the DataPort device controlling the
amplifier.
The ‘POWER’ LED is located at the upper-left of
the gain controls section of the front panel. It is a
green LED that illuminates when the power is
turned on (and the amplifier is properly connected
to the correct AC source). The power LED extin-
guishes when the power is turned off.
16
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OPERATION: LED INDICATORS
LED Indicators
The LED indicators provide basic operation information to the operator. The ‘nor-
mal’ indications of the LED’s are shown, below. NOTE! The BRDG and PAR mode
indicator LED’s are discussed on page 9.
If no indication: Check AC power cord, AC mains, and
that the DataPort is not being used to force the
amplifier into ‘Standby’ mode.
POWER: The power ‘on’ indicator LED is located at the
upper-left of the gain control cluster. It is green and
illuminates when the power switch is set to the on
position and AC power is present at the IEC cord
receptacle.
When power is switched off: the LED may take
several seconds to extinguish (go out); this is normal.
Normal indication: at power-on the LED will illumi-
nate.
SIGNAL: Each channel has a green ‘signal’ LED
located to the right of its gain control. The ‘signal’ LED
lights up when the input signal is sufficiently strong.
If no indication: check gain settings, input cables,
connections and audio source. If audio source is
extremely low signal strength, signal LED may not
illuminate; this is normal but indicates that the input
Normal indication: illuminates when the input signal signal strength should be increased.
is present and sufficiently strong.
Occasional illumination: normal for weak input
signal strength.
Fully illuminated (on): normal.
If no indication: normal if the amplifier is operated at
nominal output levels. If the input signal is weak, it may
not be capable of driving the amplifier into clipping,
even at full gain.
CLIP : Each channel has a red ‘clip’ LED that illumi-
nates when the channel clips. It is located to the upper-
right of each channel’s gain control.
Normal indication: illuminates briefly at extreme
output power peaks. Occasional clipping at high power
levels may be normal. At power-on, the clip LEDs may
briefly flash during turn-on muting.
Occasional illumination: Occasional clipping (once
briefly every few seconds) when operation at high
power levels does not indicate trouble. Continuous
operation at high power may trigger the thermal
protection circuitry, shutting down the amplifier and
fully illuminating the clip LED.
Continuous operation at high power may trigger the
thermal protection circuitry, shutting down the amplifier
and fully illuminating the clip LED. Operation will
resume after the amplifier has cooled down sufficiently.
Illuminated most of the time: Not normal; for cleaner
sound, reduce the output of the amplifier and/or input
signal to avoid thermal shutdown of the amplifier and
possible speaker damage. If clipping persists at normal
levels, check for shorted or abnormal load impedances.
Fully illuminated (on): Amplifier is in thermal shut
down. Reduce gain settings or input signal and allow
the amp to cool down. Leave the power on so that the
fan continues to run; operation will automatically
resume after the amplifier has cooled sufficiently.
17
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OPERATION: GAIN CONTROLS
Gain Controls
The gain controls are located on the right side of the front
panel. They are operated by rotating the control clockwise to
increase gain or counterclockwise to decrease gain. When
turned fully counterclockwise, gain is fully reduced and no
output signal will be present. When turned fully clockwise,
the voltage gain of the amplifier is +26dB and the output
signal will potentially be full strength (provided the input is
fully driven).
The gain controls are detented in 21 steps for repeatable
adjustment. Surrounding the Gain control, the power
attenuation level is shown in dB. Each detent is approxi-
mately 1dB change in amplifier gain.
Location of gain controls on the front panel of the CX168
To operate the gain control, rotate the control’s knob so that
the desired level is achieved. A small, flat-tipped screw-
driver (#1 blade size) is typically used. Be sure not to use
large screwdrivers as it is possible to damage the gain
control by applying excessive torque. Gain controls are
sensitive, electronic components and should be treated with
care.
Each channel pair’s gain controls and indicator LED’s are
grouped together as shown, right. The channels are paired
in the following manner:
Channel Pair #1- Ch. 1 and Ch. 2
Channel Pair #2- Ch. 3 and Ch. 4
Channel Pair #3- Ch. 5 and Ch. 6
Channel Pair #4- Ch. 7 and Ch. 8
As detailed in the ‘Setup’ section of this manual, channels
can only be paralleled and bridged within their channel pair. Typical channel-pair control and indicator group on the CX168
Example- Channel 3 can be bridged with channel 4 only; it
can not be bridged with any other channel.
The dB markings around the gain controls are attenuation.
They show attenuation from full gain. At 0db attenuation,
the voltage gain of the amplifier is 26dB. If the gain control
is set at the 7dB attenuation position, then the voltage gain
of the amplifier is 19dB (26dB - 7 dB).
Typical gain control showing attenuation level
markings and LED’s for the channel. Note that
there is only one BRDG (bridge) and one PAR
(parallel) indicator per channel pair.
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OPERATION: GAIN CONTROL SECURITY PLATE
Gain Control Security Plate
After final gain adjustments have been made, the gain controls can be covered with a security plate. This easy-to-use security plate
makes it difficult for others to adjust the gain. This may be desirable in instances where the gain controls should not be tampered with. To
install the security plate:
3. Line up the tabs with the keyed portion of the
ventilation slots, insert into the slot and then slide
the panel fully right, locking it in the slot.
1. Use a 9/64” or 3.5mm hex key to loosen
the screw. Do not remove; just loosen sev-
eral turns.
2. Orient the panel as shown and slide the right end
of the plate under the screw.
4. Make sure the LED’s are visible, then tighten the
screw with the hex key. Do not over tighten!
When properly installed, the security panel will still allow you
to monitor all the channel status LED’s and power LED. The
amplifier front panel will look like the illustration, right, after
installing the security plate.
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OPERATION: USING THE QSC DATAPORT CONNECTIONS
DataPort Connectors
QSC’s DataPort equipped amplifiers offer operators of larger
audio systems a high degree of system monitoring and
operation from remote locations. A system operator in a
sports complex might be located hundreds of yards (meters)
from the actual amplifiers, making ‘normal’ control and
monitoring of the system difficult, at best. By integrating
QSC’s DataPort-equipped amplifiers with QSC’s DataPort
accessories, a dependable and robust control and
monitoring solution can easily be implemented.
The DataPort is used for connection to optional QSC
DataPort accessories. DataPort accessory devices can
provide remote cinema monitoring, DSP, filter and crossover
A single DataPort is assigned to each channel pair. Each DataPort
functions.
is marked with the channel numbers served by that DataPort. Note,
above, that each DataPort is clearly labeled and is located be-
tween its respective channel’s terminal block connectors.
The DataPort connections on the CX168 offer full-featured
implementation of DataPort accessories and supply the
required accessory voltage to DataPort devices that require
it. CX168 amplifiers DO NOT support direct mounting of
smaller accessories, like the DSP-3, due to the high density
of connectors on the rear panel but they may be connected
via cables.
Using the DataPort
Use a QSC DataPort cable to connect the CX168 DataPorts
to DataPort accessories. Consult the accessory’s
documentation for recommended mounting and interconnect
information.
Do not use terminal block connections for inputs when the
DataPort is used as the input signal source. If you do, the
signals from the DataPort and terminal block inputs will be
mixed, possibly with unexpected results.
See the following section for general operating notes
regarding the DataPorts on the CX168.
Connect to the DataPort using a QSC DataPort cable. Align the
connector with the socket housing and insert fully. Finger-tighten
the retaining screws.
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OPERATION: USING THE QSC DATAPORT CONNECTIONS
What Can I Connect to the DataPort?
Consult your QSC representative for up-to-date accessory compatibility. QSC has several DataPort-based accessories
available like the:
CM16a Amplifier Controller & Monitor
DSP-3 Digital Signal Processing Module
DSP -30 Digital Signal Processor
XC-3 Crossover
SF-3 Subwoofer Filter
LF-3 Low Frequency Filter
DCM Crossovers & Monitors
General Guidelines to using the DataPorts on the CX168
1. Each channel pair ( Ch.1-2, Ch.3-4, Ch.5-6, and Ch.7-8) has its own dedicated DataPort connector that applies
control and monitoring functions to its specific channel pair.
2. The DataPort for channels 1 and 2 has a special function on the CX168. It is the ‘master’ DataPort for controlling
AND reporting power supply status of the amplifier. It is only possible to control and report the status of the power
supply using the Ch.1 & Ch.2 DataPort.
3. In order for the Ch.1 & Ch.2 DataPort to control the power status of the amplifier, the front-panel power switch
MUST be in the ON position. If the power switch is in the ‘off’ position, the amplifier will not respond to any com-
mands sent to its Ch.1 & Ch.2 DataPort.
4. The DataPort connection can be used for amplifier status monitoring only, using the terminal block inputs for
supplying input signals to the amplifier. Ensure that the DataPort connection supplies NO INPUT SIGNAL when
operating in this fashion. If signal is applied to both the DataPort and the terminal block input connector at the same
time, the signals will be summed and amplified. The result may be undesirable.
5. If using the DataPort for supplying the audio input signals to the amplifier, we don’t recommend using the terminal
block input connectors, even if they are connected to non-operating audio sources. The DataPort and terminal block
inputs are connected in parallel and isolated by about 20k ohms of resistance. Even with this isolation, it is possible
that connection to other signal sources may significantly alter the input impedance at the DataPort. This could affect
output levels as connections are altered.
6. If using the DataPort for supplying the audio input signals to the amplifier, do not use the unused terminal block
inputs for daisy-chaining the DataPort signals to other channel pairs or other amplifiers. The DataPort device
supplying the audio signal will not accurately report gain and levels will be effected.
7. The heat sink temperatures of the CX168 are reported on the first channel of each channel pair’s DataPort. In other
words, to monitor all four heat sink temperatures, all four DataPorts must be connected to the monitoring device (such
as QSC’s CM16a). Temperatures will be reported on channels 1, 3, 5 and 7.
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APPLICATIONS: TYPICAL APPLICATION EXAMPLES
Four Room Stereo Feed
A simple application of the CX168 would be an installation with 4 rooms of coverage; each room to be provided with a stereo
audio feed. All speakers are 4 ohm or greater impedance and have a frequency response rated down to 45 Hz., making them
suitable for the 70 Hz. low frequency setting. Clip limiting will be used with these full-range speakers. Operating mode of all four
channel pairs will be set to ‘stereo’ because the audio inputs are stereo and a stereo result is desired in each room.
Input connections can vary too much to provide meaningful examples. For this example, assume that each input has its own
discrete signal provided at the terminal block input connectors.
Routing would make sense if kept in room number order:
Room #1:
Room #2:
Room #3:
Room #4:
Fed by channel pair #1 (Ch.1&2)
Fed by channel pair #2 (Ch.3&4)
Fed by channel pair #3 (Ch.5&6)
Fed by channel pair #4 (Ch.7&8)
MODE switch configuration:
Ch.1/ Ch.2 mode switch:
Clip Limiters ON
Low Frequency Filter ON
Low Frequency Setting 70 Hz.
Mode: stereo
Ch.3/Ch.4 mode switch:
Ch.5/Ch.6 mode switch:
Ch.7/Ch.8 mode switch:
same as first mode switch
same as first mode switch
same as first mode switch
Tri-Amp’d Stereo Cabinets with Subwoofer Driven by Bridged Channel Pair (next page)
Two discrete 3-way (tri-amp) cabinets are to be connected to the CX168 along with an 8 ohm subwoofer cabinet.
The subwoofer will require the most amount of power and therefore will be driven by two channels bridged into one. Its impedance
meets the minimum requirement for bridged output. All other drivers are 4 ohms or greater and meet the single channel minimum
impedance requirement. Each of the tri-amp cabinets will be driven with three discrete channels (totaling 6 channels). The total
required channel count is 8; the CX168 is the perfect tool for the job.
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APPLICATIONS: TYPICAL APPLICATION EXAMPLES
Tri-Amp’d Stereo Cabinets with Subwoofer Driven by Bridged Channel Pair (continued)
Routing is a function of ‘easiest wiring’ order and is:
LF Driver Left:
Mid Driver Left
HF Driver Left
HF Driver Right
Ch. 4
Ch. 3
Ch. 2
Ch. 1
Mid Driver Right Ch. 5
LF Driver Right
Subwoofer
Ch. 6
Bridge Ch. 7 & 8
MODE switch configuration:
Ch.1/Ch.2 Mode: Stereo
Ch.1 Clip Limiter: ON
Ch.1 LF Filter: OFF
Ch. 2 Clip Limiter ON
Ch. 2 LF filter OFF
Ch.3/Ch.4 Mode: Stereo
Ch. 3 Clip Limiter ON
Ch.3 LF Filter:
Ch. 4 Clip Limiter OFF
Ch. 4 LF filter ON
OFF
Ch. 4 LF frequency 70 Hertz
Ch. 5/Ch. 6 Mode: Stereo
Ch. 5 Clip Limiter ON
Ch.5 LF Filter:
Ch. 6 Clip Limiter OFF
Ch. 6 LF filter ON
OFF
Ch. 6 LF frequency 70 Hertz
Ch. 7/Ch. 8 Mode Bridged
Ch. 7 Clip Limiter OFF
Ch. 7 LF Filter
Ch. 8 Clip Limiter no effect in bridge
Ch. 8 LF Filter no effect in bridge
OFF
Channels 1 through 6 are configured for ‘stereo’ mode because all channels are completely separate from one another. Channels 7 and
8 are bridged to combine their power to drive the subwoofer (sub’s are the most inefficient driver and therefore require the largest
portion of the system power).
Clip limiters are used on the mid range drivers and the HF drivers because they are the most fragile and are damaged easily by clipping
events. The LF drivers and the sub’s are rugged enough to handle even prolonged clipping events without damage and thus no clip
limiting is used.
Low frequency filtering is used only on the LF drivers. The HF and mid range drivers have filtering before the amplifier and need no
filtering from the CX168. The subwoofer cabinet can handle the low frequencies without problem, so no filtering for them. The LF
drivers response specification will dictate at what frequency (33 or 70 Hz.) the low frequency filter is set for.
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APPENDIX: DESCRIPTION OF STEREO & PARALLEL OPERATING MODES
NOTE! In the following diagrams, channels 1 and 2 are shown as examples only. Any channel pair can be configured as
shown here. The channels pairs on the CX168 are : Channels 1 and 2, Channels 3 and 4, Channels 5 and 6, and Channels 7
and 8. Therefore, in any example below, replace channel 1 and 2 with the channel pair numbers you are setting up.
Stereo Mode:
Each input signal is sent to its respective channel. Each
channel has independent low-frequency (subaudio) filtering,
clip limiting, gain control, and output connection.
When to use STEREO input configuration: Use stereo
mode for stereo sources (L-R inputs) and any other situation
that requires each channel to be completely separate from
the other.
How to use STEREO mode:
1- Set the MODE switches for stereo mode operation.
STEREO MODE OPERATION
2- Connect the two input signals to CH1 and to CH2 (or
signals may be provided from DataPort connection).
NOTE: Ensure that the MODE SWITCHES are set
to STEREO when feeding two separate signals to
the two channels.
3- Connect the two speakers; one to channel 1’s output
terminals, one to channel 2’s output terminals.
Parallel Mode:
The channel 1 and channel 2 inputs are connected together,
applying a single input signal to both channels of the
amplifier. A signal into any input jack will drive both channels.
Each channel's low frequency filtering, clip limiting, and gain
control still function independently. Each channel drives its
own speaker load.
You can patch the input signal on to additional amplifiers
(daisy chain) by using any of the remaining input jacks. This
feature eliminates the need for “Y” cables.
When to use PARALLEL input configuration: Use parallel
mode when you need one signal to drive both channels; each
channel having its own control (gain, clip limiter, low-
frequency filter).
How to use PARALLEL mode:
1- Set the MODE switches for PARALLEL mode.
PARALLEL MODE OPERATION
2- Connect the one input signal to either channel’s input
connector. The unused input may be used for daisy chaining
the signal to another device or channel pair.
3- Connect the two speakers: one to channel 1’s output
terminals, one to channel 2’s output terminals.
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APPENDIX: DESCRIPTION OF BRIDGE OPERATING MODE
Bridge Mode
Bridge mode combines both output channels into one output.
This mode is for driving a single, high-power-rated load with
twice the “normal” voltage swing. This results in about 4
times the peak power and about three times the sustained
power of a single channel. It is also common to call this
bridge mono mode.
When to use BRIDGE mode: Use BRIDGE mode when you
need to deliver the power of two channels to a single 8 ohm
load, such as a subwoofer. Do not use less than 8 ohm loads
in bridge mode. Refer to the CONNECTIONS section of this
manual for details.
How to use BRIDGE mode:
BRIDGE MODE OPERATION-
1- Set the MODE switches for bridge mode.
Note that speaker connection for bridge mono mode is
different than other modes. See section on Connections:
Outputs for proper bridge mode output connections.
2- Connect the one input signal to channel 1 or channel 2’s
input.
3- Connect the one speaker load to the bridge output
terminals
4- For a bridged pair, use the first channel’s gain control, clip
limiter and filter. The second channel’s controls will have no
effect.
5- Turn the second channel’s gain to zero gain. Filters and
limiter settings of second channel do not matter.
Normal Operating Levels
The amplifier’s protective muting system guards against excessive internal temperatures. With normal ventilation and
loads, the amplifier will handle any signal level, including overdrive. Lower load impedances and higher signal levels
produce more internal heating. Loads below 4 ohm loads may trigger thermal shutdown.
A Note on Sound Pressure Levels
Sound is heard as the ear converts vibration from sound waves into
impulses in the nerves of the ear. Sounds above 90 decibels, particu-
larly if the sound is prolonged, may cause such intense vibration that
the inner ear is damaged. 90 decibels is about the loudness of a large
truck about 5 yards away. A jackhammer emits sounds of about 120
dB from 3 feet away, and a jet engine emits sound of about 130 dB
from 100 feet away. Motorcycles, snowmobiles, and similar engines
range around 85 to 90 dB, and a rock concert may approach 100 dB. A
general rule of thumb is that if you need to shout to be heard, the
sound is in the range that can damage hearing.
Some jobs in the entertainment industry involving loud noise from
music carry high risk for hearing loss. In the U.S., the maximum job
noise exposure is regulated by law. Both the length of exposure and
the extent (decibel level) of exposure are considered. If exposure is
at or greater than the maximum exposure, protective mea-
sures must be taken. The table at right is referenced from OSHA’s
Permissible Noise Exposure table G16.
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APPENDIX: MULTIPLE SPEAKER LOADS IN SERIES
Multiple Lo-Z Loads in Series:
Series connection is where the same signal current flows
through each of the speaker loads. The signal goes into one
terminal of the first speaker and out its other terminal; then the
signal goes into one terminal of the next load, and so on. If any
of the speakers in a series-connected branch of a system fails,
the signal is prevented from flowing through any of the loads (no
sound). Total impedance for series connections is the sum of
each of the impedances in the chain (see illustration, below).
speaker cabinets are NOT wired for series connection ability;
consult your speaker’s documentation for connection information.
It is not recommended to connect speakers of different imped-
ances in series because power will be divided unequally
between them. If you are experienced with mixing and matching
speaker loads of varying impedances, no damage to the amplifier
will result as long as the total impedance is within 4 to 16 ohms
per stereo/parallel channel or 8 to 16 ohms, bridged.
Series connection schemes are usually used with “raw”
speakers (not often with speaker cabinets) for wiring conve-
nience. The exposed speaker connections make this method
easy for small “strings” of speakers in one area. Most PA-type
Below are examples of series connections for 2, 4, 8, and 16 ohm
speaker loads. Series connections resulting in an impedance of
250 ohms or greater are not recommended.
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APPENDIX: MULTIPLE SPEAKER LOADS IN PARALLEL
Multiple Lo-Z Loads in Parallel:
If each speaker load is connected across the same signal source
(the output of the amplifier), then the loads are in parallel with
one another. If one of the speakers fails in a parallel-connected
system branch, the remaining speakers will continue to operate.
If all speaker loads are the same impedance, the total imped-
ance of a parallel-connected system branch is the impedance of
one speaker load divided by the number of loads in the branch
(example: three 8-ohm loads in parallel: 8/3=2.667 or roughly 2.7
ohms, too low to use on the CX168).
Most PA-type speaker cabinets are provided with two or more
input jacks that are wired in parallel. If one cabinet is connected
to the amplifier, the load impedance is equal to the one cabinet’s
specified impedance. If you attach another similar cabinet to the
remaining jack of the first cabinet, the two cabinets are now in
parallel with each other and the impedance will be half of the
one-cabinet value. Consult your speaker’s documentation for
connection details as there are many connection methods in use.
Below are examples of parallel connections of 4, 8 and 16 ohm
speakers. 2 and 4 ohm parallel loads are not usable because the
parallel impedance of 4 ohm loads will always be 2 ohms or less;
this is too low an impedance for the CX168 amplifier.
It is not recommended to connect speakers of different imped-
ances in parallel because power will be divided unequally
between them. If you are experienced with mixing and matching
speaker loads of varying impedances, no damage to the
amplifier will result as long as the total impedance is within 4 to
16 ohms per channel, dependant upon operating mode.
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TROUBLESHOOTING: NO SOUND
Problem: NO SOUND
• INDICATION: POWER LED INDICATOR NOT ILLUMINATED
• Check both ends of the AC line cord for proper connection. Both ends should be fully seated in their connectors.
• Check that the AC outlet works by plugging in a known-good device or by testing with a voltmeter. If too many amplifiers are used on
one outlet, the building's circuit breaker may trip and shut off power. If this is the case, unplug some of the amplifiers from the outlet,
reset the building’s breaker and try again. For the other amps, use an outlet that is connected to another circuit breaker to distribute
the load current.
• If using the DataPort connections, the channel 1 and 2 DataPort controls the power supply of the amplifier. Check whether or not the
DataPort accessory connected to the CX168 is forcing the power supply into standby mode.
• An amplifier which keeps tripping the AC circuit breaker may have a serious internal fault. Turn it off, remove AC power, and have the
amplifier serviced by a qualified technician.
• INDICATION: SIGNAL LED’S NOT RESPONDING TO INPUT SIGNAL LEVEL (NOT LIGHTING)
• If the green power indicator LED is lit, but the signal LEDs do not light up at all, check the input. Make sure the signal source is
working and try another input cable. Connect the source to another channel or amplifier to check that it is working.
• If you are using the terminal block inputs, be sure the connectors are fully inserted at both ends of all interconnecting cables. If you
are using the DataPort for your input signal, ensure the DataPort cable is properly connected at both ends and that the device
supplying the audio signal to the DataPort is properly configured.
• Check gain controls.
• INDICATION: SIGNAL LEDS RESPONDING TO SIGNAL LEVEL
• If the green signal LED indicators are lighting normally, the fault is somewhere between the amplifier and the speakers. Check the
speaker wiring for breaks. Check for proper connection at each end. Try another speaker and cable, if necessary. If your system has
multiple speakers connected in series, any one speaker failure will cause all other speakers (in the same series circuit) to lose their
signal.
• INDICATION: CLIP LED FLASHING
• If the red clip indicator flashes when signal is applied, the amplifier output may be shorted. Check that the speaker cable connec-
tions are tight and reliable at both ends. Check the speaker cables for stray strands or breaks in the insulation. Trim off all loose
strands of wire and insulate any exposed wire with electrical tape. All connections should be made with great care and all wire
terminations should be carefully checked to ensure quality workmanship.
• If the red clip indicator flashes when connecting the speaker cable between the + and - terminals, then that speaker cable (or
speaker) may be shorted. Check the cable and the speaker.
• INDICATION: CLIP LEDS BRIGHT AND STEADY
The amplifier is in protective muting.
• Three seconds or so of muting is normal when the amp is turned on. After power-up muting, the Clip LED‘s should go out.
• Overheating will cause protective muting and the Clip LED to fully illuminate. If the amp is overheated, the fan will be running at full
speed and the chassis will be very warm to the touch; sound should resume within a minute as the amplifier cools to a safe
operating temperature. DO NOT TURN THE AMP OFF! This would stop the fan from cooling the inside of the amplifier. Instead,
reduce the input signal ( or amp gain setting) and wait for the amp to resume operation automatically.
• Check for proper ventilation. If the fan isn't running at all, the amplifier requires servicing.
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TROUBLESHOOTING: DISTORTION, NO CHANNEL SEPARATION, HUM, HISS, FEEDBACK
PROBLEM: DISTORTED SOUND
• INDICATION: CLIP LED FLASHING
• If the red clip indicator flashes before the signal indicator does, the load impedance is abnormally low or shorted. Unplug each speaker
one-by-one at the amplifier. If the clip LED goes out when you disconnect a cable, then that cable or speaker is shorted. Try another
cable and speaker to locate and/or remove the fault.
• INDICATION: CLIP INDICATOR NOT FLASHING
• This could be caused by a faulty speaker or loose connection. Check the wiring and try another speaker.
• The signal source may be clipping. Keep the amplifier gain controls at least halfway up (-10 dB or less) so that the source does not
have to be overdriven.
PROBLEM: NO CHANNEL SEPARATION
• Check the mode switch settings on the back of the amplifier. If the mode switches are set for BRIDGE or PARALLEL mode, there
will be no channel separation. The mode switches must be set for STEREO for each channel to operate independently.
• Make sure other equipment in the signal path to the amplifier, such as mixers, preamps, etc., is set for stereo, not mono.
PROBLEM: HISS
• Unplug the input cables to the amplifier. If the hiss goes away, then the problem is with the equipment or cables leading to the
amplifier.
• If the hiss is present with no audio input cables connected, check that the AC line cord is properly grounded at its connection to
the line. If the ground connection is OK and the hiss continues with no input cables connected, then the amplifier requires
servicing.
• To keep the normal noise floor low, operate the primary signal source at full level, without clipping, and avoid boosting the
signal further between the source and the amplifier.
PROBLEM: SQUEALS AND FEEDBACK
• Microphone feedback should be controlled with mixer controls. If noise continues to build up with zero mic gain, there is
a serious fault in the signal processors or cables. Working in succession from the signal source towards the amplifier,
check each device in the signal path by reducing its gain or unplugging it.
PROBLEM: HUM
• Use a common AC ground connection for all audio equipment.
• Check the input cables for broken ground (shield) connection.
• Use balanced connections for the entire signal chain.
• The design of the amplifier eliminates internal hum fields, but
external transformers or other magnetic devices may cause hum.
Move cabling and signal sources to identify "hot spots" in the
system; then avoid those spots. Cables with faulty shielding are a
common entry point for hum. Use top quality cabling. Another
common source of magnetic fields are “wall warts” or pluggable
Magnetic field from power supplies in equipment can
induce hum into cabling that is located in the field. If
hum is a problem, try relocating cabling so that is away
from power supplies, transformers and other magnetic
transformers; keep input wiring away from them.
field producing devices.
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SPECIFICATIONS
CX168
OUTPUT POWER in watts
FTC:
8 ohms per channel (20 Hz.-20 kHz., 0.05% THD)
90
4 ohms per channel (20 Hz.-20 kHz., 0.1% THD)
8 ohms (1 kHz, 0.1% THD, 1 channel driven)
4 ohms (1 kHz, 0.1% THD, 1 channel driven)
130
EIA:
120 (100 watts, all channels driven)
180 (140 watts, all channels driven)
Bridged Mono:
16 ohms, 20 Hz.-20 kHz., 0.1% THD
180
8 ohms, 20 Hz.-20 kHz., 0.1% THD
DYNAMIC HEADROOM
260
2 dB at 4 ohms
DISTORTION
SMPTE-IM
Less than 0.02%
Less than 0.05%
Less than 0.02%
Typical 20 Hz.-20 kHz., 10 dB below rated power
Typical 1 kHz. and below, full rated power
FREQUENCY RESPONSE
+0.0, -3.0 dB: 8 Hz. to 50 kHz.
0.2 dB: 20 Hz.-20 kHz.
DAMPING FACTOR
>200 for 8 ohm load (5 kHz. and below)
-107 dB
SIGNAL to NOISE (unweighted, 20 Hz.-20 kHz.)
VOLTAGE GAIN (gain control set to 0 dB attenuation)
26 dB (20 X)
1.35 Vrms
INPUT SENSITIVITY for rated power into 8 ohms
INPUT CLIPPING, Vrms
INPUT IMPEDANCE
10 Vrms (+22 dBu)
10k ohms unbalanced , 20k ohms balanced
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SPECIFICATIONS
CX168
AMPLIFIER PROTECTION
Full short circuit, open circuit, thermal, ultrasonic and RF protection.
Stable into reactive or mismatched loads.
COOLING
Continuously variable speed fan; back-to-front air flow through tunnel heat sink
INDICATORS
Front Panel: POWER LED (green), 8 each (1 per channel) SIGNAL (green) and CLIP (red) LEDs
4 each (1 per channel pair) BRDG LED (yellow), 4 each (1 per channel pair) PAR LED (orange)
CONNECTORS
Input: (8) 3-pin terminal block (“euro” or “Phoenix”)
Output: (2) 8-pin detachable terminal block connectors
Control & Monitoring: (4) QSC DataPort connectors
LOAD PROTECTION
Turn-on/turnoff muting
AC coupling (DC fault blocking)
Clip limiting
OUTPUT CIRCUIT TYPE
POWER REQUIREMENTS
AB + B
SEE SERIAL NUMBER LABEL ON REAR PANEL FOR THE SPECIFIED OPERATING VOLTAGE
Configured at factory for either 100, 120 or 230 VAC, 50- 60 Hz.
CURRENT CONSUMPTION @ 120 VAC, typical
(both channels driven) in Amperes
Idle
0.6
6.2
9.2
9.2
14.2
1/8 power, 8 ohms*
1/8 power, 4 ohms*
1/3 power, 8 ohms*
1/3 power, 4 ohms*
NOTE: 1/8 power is representative of current draw with typical music program material with occasional clipping. *Pink noise
1/3 power is representative of program material with severe clipping.
CONTROLS
Front: AC POWER switch, (8) gain controls
Back: (4) DIP switch blocks with 10 poles (1 per channel pair): Clip Limiters, Stereo/Parallel/Bridge mode
selection, low frequency filter on/off and frequency selection.
DIMENSIONS
WEIGHT
19.0" (48.3 cm) wide, 3.5" (8.9 cm) tall (2 rack spaces)
14" (35.6 cm) deep (from front mounting rails) including rear support ears
21 pounds ( 9.5 kg) net, 27 pounds ( 12.3 kg) shipping
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
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WARRANTY INFORMATION & HOW TO CONTACT QSC
(USA only; other countries, see
WARRANTY
your dealer or distributor)
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 ISA amplifier.
Product Warranty
QSC guarantees the CX168 amplifier to be free from defective material and/or workmanship for a period of three years from the
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 a copy of the
proof of purchase, i.e., sales receipt. This warranty provides that examination of the returned 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.
HOW TO CONTACT QSC AUDIO PRODUCTS
Mailing address / Adresse postale / Postanschrift / Dirección postal:
QSC Audio Products, Inc.
1675 MacArthur Boulevard
Costa Mesa, CA 92626-1468 USA
Telephone Numbers / Numéros de téléphone / Telefonnummern / Números de teléfono:
Main Number / Numéro principal / Hauptnummer / Número principal
+(714) 754-6175
+(714) 957-7100
Sales Direct Line / Ligne directe ventes / Verkauf-Direkt / Línea directo ventas
Sales & Marketing / Ventes & marketing / Verkauf u. Marketing / Ventas y marketing
(800) 854-4079
(toll-free in U.S.A. only)
(sans frais aux É-U seulement)
(zollfrei nur beim USA)
(sin costo en EE. UU. solamente)
Customer Service / Service à la clientèle / Kundendienst / Servicio a la clientela
+(714) 957-7150
(800) 772-2834
(toll-free in U.S.A. only)
(sans frais aux É-U seulement)
(zollfrei nur beim USA)
(sin costo en EE. UU. solamente)
Facsimile Numbers / Numéros de télécopieur / Telefaxnummern / Número de FAX:
Sales & Marketing FAX / Télécopie ventes & marketing / Telefax der Verkauf u. Marketing / FAX ventas y marketing
+(714) 754-6174
Customer Service FAX / Télécopie service à la clientèle / Kundendienst-Telefax / FAX servicio a la clientela
+(714) 754-6173
World Wide Web:
E-mail:
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NOTES
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NOTES
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QSC Audio Products, Inc. 1675 MacArthur Boulevard Costa Mesa, California 92626 USA
“QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office.
©2000 QSC Audio Products, Inc.
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