QSC CMX 300Va User manual

CMXa Series
User Manual
CMX 300Va
CMX 500Va
CMX 800Va
CMX 2000Va
*TD-000409-00*
TD-000409-00-A

2
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EXPLANATION OF SYMBOLS
The term “WARNING!” indicates instructions regarding personal safety. If the instructions are not followed the result may be bodily injury or death.
The term “CAUTION!” indicates instructions regarding possible damage to physical equipment. If these instructions are not followed, it may result in
damage to the equipment that may not be covered under the warranty.
The term “IMPORTANT!” indicates instructions or information that are vital to the successful completion of the procedure.
The term "NOTE" is used to indicate additional useful information.
The intent of the lightning flash with arrowhead symbol in a triangle is to alert the user to the presence of un-insulated "dangerous"
voltage within the product's enclosure that may be of sufficient magnitude to constitute a risk of electric shock to humans.
The intent of the exclamation point within an equilateral triangle is to alert the user to the presence of important safety, and operating
and maintenance instructions in this manual.
IMPORTANT SAFETY INSTRUCTIONS
WARNING!: TO PREVENT FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE.
• Read these instructions
• Keep these instructions.
• Heed all warnings.
• Follow all instructions.
• Do not use this apparatus near water.
• Clean only with a dry cloth.
• Do not block any ventilation opening. Install in accordance with the manufacturer's instructions.
• Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat.
• Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A
grounding type plug has two blades and a third grounding prong. The wide blade or the third prong are provided for your safety. If the provided
plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet.
• Protect the power cord from being walked on or pinched particularly at plugs, convenience receptacles, and the point where they exit from
the apparatus.
• Only use attachments/accessories specified by the manufacturer.
• Unplug this apparatus during lightning storms or when unused for long periods of time.
• Refer all servicing to qualified service personnel. Servicing is required when the apparatus has been damaged in any way, such as power-supply
cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture,
does not operate normally, or has been dropped.
• The appliance coupler, or the AC Mains plug, is the AC mains disconnect device and shall remain readily operable after installation. On units
equipped with powerCon® connectors, the AC Mains disconnect device is the AC Mains plug only; do not use the appliance coupler.
• Adhere to all applicable, local codes.
• Consult a licensed, professional engineer when any doubt or questions arise regarding a physical equipment installation.

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RoHS Statement
The CMX 300Va, CMX 500Va, CMX 800Va and CMX 2000Va amplifiers are in compliance with European Directive 2002/95/EC – Restriction of
Hazardous Substances (RoHS).
The CMX 300Va, CMX 500Va, CMX 800Va and CMX 2000Va amplifiers are in compliance with “China RoHS” directives. The following chart is provided
for product use in China and its territories:
CMXa
部件名称
(Part Name)
有毒有害物质或元素
(Toxic or hazardous Substances and Elements )
铅
(Pb)
汞
(Hg)
镉
(Cd)
六价铬
(Cr(vi))
多溴联苯
(PBB)
多溴二苯醚
(PBDE)
电路板组件
(PCB Assemblies) XOXOOO
机壳装配件
(Chassis Assemblies) XOXOOO
O:表明这些有毒或有害物质在部件使用的同类材料中的含量是在SJ/T11363_2006极限的要求之下。
O: Indicates that this toxic or hazardous substance contained in all of the homogeneous materials for this part is below the limit requirement in SJ/
T11363-2006.
X:表明这些有毒或有害物质在部件使用的同类材料中至少有一种而含量是在SJ/T11363_2006极限的要求之上。
X: Indicates that this toxic or hazardous substance contained in at least one of the homogeneous materials used for this part is above the limit
requirement in SJ/T11363-2006.
FCC Statement
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 be 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 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.

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Warranty (USA only; other countries, see your dealer or distributor)
QSC Audio Products 3 Year Limited Warranty
QSC Audio Products, LLC (”QSC”) guarantees its products to be free from defective material and/or workmanship 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, one of our authorized service stations or an authorized QSC International Distributor via pre-paid 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. This limited warranty is freely transferable during the term of the warranty period. The warranty on QSC products is NOT VALID if the products
have been purchased from an unauthorized dealer/online e-tailer, or if the original factory serial number has been removed, defaced, or replaced in
any way. Damage to, or loss of any software or data residing on the product is not covered. When providing repair or replacement service, QSC will
use reasonable efforts to reinstall the product’s original software configuration and subsequent update releases, but will not provide any recovery or
transfer of software or data contained on the serviced unit not originally included in the product.
Customers may have additional rights, which vary from state to state or from country to country. In the event that a provision of this limited warranty is
void, prohibited or superseded by local laws, the remaining provisions shall remain in effect.
The QSC limited warranty is valid for a period of three (3) years from date of purchase in the United States and many (but not all)
other countries.
For QSC warranty information in countries other than the United States, contact your authorized QSC international distributor. A list of QSC
International distributors is available at www.qsc.com.
To register your QSC product online, go to www.qsc.com and select ”Product Registration”. Other questions regarding this warranty can be answered
by calling, e-mailing or contacting your authorized QSC distributor.
Phone: [phone] within US and Canada, [phone] international, Email: [email protected], Website: www.qsc.com.

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Introduction
These rugged, fan-cooled, 2-channel, 2RU/3RU amplifiers provide high-value performance and power in a strong, compact chassis. The series
comprises four models: the CMX 300Va, CMX 500Va, CMX 800Va and CMX 2000Va.
Features
CMX 300Va CMX 500Va CMX 800Va CMX 2000Va
Stereo Mode (both channels driven)
8/ FTC 20 Hz - 20 kHz / 0.1% THD
8/ EIA 1 KHZ / 0.1% THD
4/ FTC 20 HZ - 20 KHZ / 0.1% THD
4/ EIA 1 KHZ / 0.5% THD
4/ EIA 1 KHZ / 1% THD
2/ EIA 1 KHZ / 1% THD
70 V - Direct drive / EIA 1 kHz / 1% THD
100 V - Direct drive / EIA 1 kHz / 1% THD
185 W
200 W
280W
300 W
430 W
-
260 W
300 W
400 W
500 W
700 W
-
450 W
500 W
650 W
800 W
1200 W
400 W
1050 W
1100 W
1600 W
2000 W
2500 W
2500 W
1000 W
Bridge Mono Mode
8/ FTC 20 Hz - 20 kHz / 0.1%THD
8/ EIA 1 kHz / 0.1%THD
4/ EIA 1 kHz / 1%THD
70 V - Direct drive / EIA 1 kHz / 1% THD
100 V - Direct drive / EIA 1 kHz / 1% THD
140 V - Direct drive / EIA 1 kHz / 1% THD
530 W
600 W
830 W
600 W
-
800 W
900 W
1400 W
1200 W
600 W
1300 W
1500 W
2400 W
2000 W
2300 W
3200 W
3600 W
5000 W
3600 W
5000 W
— Table 1 —
• Independent, user-defeatable clip limiters
• Fully selectable low-frequency filtering; choice of 30 or 50 Hz roll-off
• Stereo (dual-channel), parallel-input, or Bridge Mono
operating modes
• Balanced inputs — XLR, ¼" (6.3 mm) TRS, and barrier strip
• Pluggable terminal block and NL4 outputs
• 21 detent gain knobs
• Front panel LED indicators for signal and clip and power
• Attenuation control security plate

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Front Panel
1. Power switch
2. Power indicator LED
3. Cooling vents
4. Clip and Signal indicator LEDs, (Channel 1)
5. Attenuation controls (Channel 1)
6. Clip and Signal indicator LEDs, (Channel 2)
7. Attenuation control (Channel 2)
8. Lockout plate retention screw
— Figure 1 —
87654321
— Figure 2 —
2
3468
7 5 1 8
Back Panel
1. Barrier strip input
2. XLR inputs, Channels 1 and 2
3. TRS inputs, Channels 1 & 2
4. Configuration dip switches
5. Fan
6. NL4 output, Channel 1 and 2
7. Terminal block connector outputs, Channels 1 and 2
8. Circuit Breaker
9. Serial number label
10. Configuration switch chart
11. IEC power inlet (power cord connector)
— Figure 3 —
123 64 5 7 8 10 119

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Features and Setup
Attenuation Control Security Plate
The Attenuation control security plate (— Figure 4) provides protection against accidently adjusting the Attenuation controls on the amplifier face.
Attach the plate, after making final adjustments to the Attenuation controls, by sliding the tabs into the installation slots. Secure in place with the
attachment screw.
Setting the Mode Switches
The CMXa has mode switches for STEREO, PARALLEL INPUTS, or BRIDGE MONO modes. Each channel has independent clip limiting and low
frequency filtering.
Clip Limiter
What it is
When the audio signal drives the amplifier's output circuit beyond its power capability, it clips,
flattening the peaks of the waveform. The clip limiter detects this and reduces the gain to
minimize the amount of overdrive. To preserve as much of the program dynamics as possible,
limiting reduces the average program level until peaks barely clip.
Each channel has its own clip limiter, and you can switch it on or off independently, as shown
in — Figure 5.
When to use it (or not)
When driving full-range speakers, clip limiting reduces high-frequency distortion caused by bass overloads. It also protects higher frequency drivers
from excess overdrive and harsh clipping harmonics.
When driving subwoofers, some users let the amplifier clip without limiting because it gives extra “punch” to kick drums and similar sounds.
CAUTION: In bi-amp systems, excessive limiting will affect the frequency balance.
— Figure 4 —
— Figure 5 —

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Input Low-Frequency Filter
What it is
The low-frequency (LF) filter rolls off signals below either 30 Hz or 50 Hz (— Figure 8 and — Figure 9).
This improves bass performance by limiting sub-audio cone motion, making more power available for
the speakers' rated frequency range.
The filter settings for each channel are controlled individually through the DIP switch settings shown
in — Figure 6. When the filter is turned off (— Figure 7), a 5 Hz roll off protects against DC or deep
sub-audio inputs.
When to use it (or not)
As a rule, your speakers will sound better with proper
filtering. Unless you already have filtering in a preceding
device, match the setting to the low frequency rating of
your speakers. Vented (bass reflex, ported, etc.) speakers
are especially sensitive to cone over-excursion at
frequencies below their rated limit.
The 50 Hz filter works well with most compact full-range
speakers, and has a slight boost at 100 Hz for greater
fullness. The 30 Hz filter is intended for subwoofers and
large full-range cabinets. The “off” position should be used
only for applications such as studio playback monitoring,
where you need to know if there are unwanted sub-audio
signals present in your mix.
— Figure 6 —
— Figure 7 —
— Figure 8 —
— Figure 9 —

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Parallel Input Mode
What it is
The Parallel Input switches let you operate the amplifier in Parallel mode, delivering the same
signal to both channels without using a Y cable. Each channel drives its own speaker load, with
independent gain, filtering, and clip limiting.
Set switch positions 4 and 5 to "PARALLEL INPUTS" to couple the inputs together (— Figure 10).
Turn the switches to "STEREO" for stereo, bi-amping, or other 2-channel modes.
With the inputs in parallel, you can use the other set of input connectors to carry the signal to
other amps (— Figure 11). This is often called a “daisy-chain.”
When to use it
Use the Parallel mode when driving two speakers with one input signal (Parallel mode) while keeping separate control of both channels' gain, filtering,
and limiting. Use Parallel mode and Bridge Mono mode to patch the signal to additional amplifiers through the extra input jacks.
NOTE: If you're using a balanced signal, use only balanced patch cables; even one unbalanced cable will unbalance the entire signal
chain, possibly causing hum.
NOTE: Turn off the “Parallel Inputs” switches when feeding the amp two separate signals.
— Figure 10 —
— Figure 11 —
Amp 1 Amp 2

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Bridge Mono Mode
What it is
Bridge Mono mode combines the power of both amp channels into one speaker, resulting in
twice the voltage swing, four times the peak power, and approximately three times the sustained
power of a single channel. This mode uses Channel 1's input, attenuation control, input filter, and
clip limiter; Channel 2's dip switch settings should be in the OFF position, the attenuation control
should be at maximum attenuation (— Figure 12 and — Figure 13).
When to use it (or not)
Use Bridge Mono mode to deliver the power of both channels to a single 8 or 4load. Set
switch positions 6 and 7 to BRIDGE MONO ON (— Figure 12). Use Channel 1's inputs, and
connect the loudspeaker as shown in — Figure 14 or — Figure 15).
Bridge Mono Precautions
This mode puts a high demand on the amplifier and speaker, Excessive clipping may cause
protective muting or speaker damage. Be sure the speaker has a sufficient power rating.
WARNING!: Output voltages greater than 100 volts RMS are available
between the bridged terminals of the CMXa. CLASS 3 wiring methods (NEC
1999), as specified in accordance with national and local codes, must be used
to connect the speaker.
Channel 2 settings, switches
8, and 10 are set to off.
— Figure 12 —
To patch the signal to additional amplifiers, use
the parallel input switches described under
Parallel Input Mode.
— Figure 13 —
— Figure 14 —
— Figure 15 —

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The Difference Between Modes
Stereo Mode
Stereo mode is the typical way of using the amplifier. Each channel is fully independent. Separate signals connect at the inputs, the attenuation knobs
control their respective channels, and separate speakers connect to each output. The dip switches are set as shown in — Figure 16, a schematic
illustration in — Figure 17.
Examples:
• Two-channel (stereo) playback.
• Two independent mono signals, such as main and monitor mixes.
• Bi-amped operation, with the low frequencies in Channel 1 and the highs in Channel 2.
Parallel Input Mode
This mode is similar to the Stereo mode, except that the inputs for Channel 1 and Channel 2 are internally connected together. A signal into Channel
1 jack drives both channels directly (— Figure 18). Use Channel 1 Input, do not connect different sources to both channels. Each channel's attenuation
control still functions as usual, and each channel feeds its own speaker load. The dip switches are set as shown in — Figure 19.
In Parallel mode, you can patch the input signal on to additional amplifiers by using any of the remaining input jacks. See Ch. 2 in — Figure 18.
Example:
One mono signal driving both channels, with independent attenuation control for each speaker system.
— Figure 16 —
— Figure 17 —
— Figure 18 —
Can be used to Daisy-chain additional amplifiers
— Figure 19 —

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Bridge Mono Mode
This mode combines the full power capabilities of both channels into a single speaker system. The
amplifier internally re-configures so that both channels operate as a unit. This delivers double the
output voltage, resulting in four times the peak power and three times the sustained power into a
single 8 or 4speaker load. The Bridge Mono mode section on page 10 describes the special
loudspeaker connection used.
Examples:
• Driving a single 8speaker with the combined 4power of both channels.
• Driving a single 4speaker with the combined 2power of both channels.
Precautions:
• Bridge Mono mode makes it possible to drive thousands of watts into a single speaker. AC
current consumption will usually be higher. Avoid excessive signal level, and make sure the wiring and speaker can handle the power.
• If the load is 4or less and prolonged overloads occur, the amplifier will probably mute for several seconds during peaks, and the circuit
breaker may trip.
• Do not use 2loads.
• Ensure Channel 2 dip switches are set to off (— Figure 20), and Channel 2 attenuation control is set to maximum attenuation.
NOTE: See the additional Bridge Mono precautions on page 10.
Distributed Constant Voltage Outputs
Please refer to the above section on Bridge Mono mode for proper setup
configuration.
70/100 Volt Operation:
• The CMX 300Va and 500Va must be configured for Bridge Mono mode for 70
Volt operation.
• The CMX 800Va and CMX 2000Va can operate in 70 Volt operation in Stereo
mode or Bridge Mono mode.
• The CMX 500Va and CMX 800Va must be configured for Bridge Mono mode
for 100 Volt operation. Please refer to the Bridge Mono mode section for proper
setup configuration.
The CMX 2000Va can operate in 70 Volt or 100 Volt operation in STEREO mode or
BRIDGE MONO mode..
Set Channel 2 dip switches,
8 and 10, to off.
— Figure 20 —
Channel 1 Input, Channel 2 Not Used
— Figure 21 —
Channel 2 Can Be Used to
Daisy-chain to Other Amplifiers.
— Figure 22 —
CMX 300Va CMX 500Va CMX 800Va CMX 2000Va
Stereo Mode (Both Channels Driven)
70 Volt - - 400 W 2500 W
100 Volt - - - 1000 W
Bridge Mono Mode
70 Volt 600 W 1200 W 2000 W 5000 W
100 Volt - 600 W 2300 W 3600 W
— Table 2 —

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Installation
Rack mounting of the amplifier is optional.
Use four screws and washers when mounting the amplifier to the front rack rails.
Support the amp at the rear also, especially in mobile and touring use; rear rack mounting ear kits are available from QSC’s technical services
department or by special order from your dealer or distributor. Use the dimensions in — Figure 23 and — Figure 24 for planning.
— Figure 23 —
3.5”
88.9 mm
17.3”
440 mm
16.3”
414 mm
2.25”
5.7 mm
15”
381 mm
19”
483 mm
— Figure 24 —
2.25”
57 mm
3.0”
76 mm
5.2”
133 mm
17.3”
440 mm
19”
483 mm
16.3”
414 mm 15”
381 mm

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Connections
Inputs
Each channel has active balanced XLR and ¼" (6.3 mm) inputs wired in
parallel (— Figure 25). The input impedance is 20 kbalanced, 10 k
unbalanced.
Balanced signals are less prone to AC hum, but unbalanced signals can be
suitable for short cable runs. The signal source’s output impedance should
be less than 600to avoid high frequency loss in long cables.
Balanced Inputs
Use the XLR or ¼" (6.3 mm) TRS input jacks, or the barrier strip (— Figure
26 through — Figure 28).
Unbalanced Inputs
• Connect the unused side (Pin 3) of the balanced input to ground (Pin 1), as shown in — Figure 26.
• A tip-sleeve ¼" (6.3 mm) connector will correctly terminate the unused side of the input as shown in — Figure 27.
• For Stereo operation, use the inputs for both Channel 1 and Channel 2. For Parallel or Bridge Mono operation, use the Channel 1 input.
• See the section on operating modes for more information. To patch the audio signal to other amps (Parallel and Bridge Mono modes only), see
the instructions for using Parallel Inputs on page 9.
— Figure 25 —
1 =
2 = +
3 =
XLR unbalanced Jumper pin 1 to pin 3
— Figure 26 —
TRS unbalanced
No modification needed
— Figure 27 —
Balanced Unbalanced
— Figure 28 —

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Outputs
NL4 Outputs
CMXa amplifiers offer a choice of output connections, with two NL4 jacks and a
Terminal Block connector.
The NL4 connector is designed specially for high-power speaker connections. It
locks in place, prevents shock hazard, and assures the correct polarity.
The upper NL4 jack has both Channel 1 and Channel 2 outputs, so it is especially
useful for Parallel, bi-amp, or Bridge Mono mode operation (see Bridge Mono
mode operating precautions on page 10). The other NL4 carries only the output
from Channel 2.
For easier insertion, use the NL4FC connectors with quick-lock thumb latches (Not
shown).
Speaker Cabling
Larger wire sizes and shorter lengths minimize both loss of power and degradation
of damping factor. Do not place speaker cables next to input wiring.
WARNING!: To prevent electric shock, do not operate the
amplifier with any of the conductor portion of the speaker
wire exposed.
Terminal Block Connector
The terminal block connector requires the following assembly.
1. Strip the wires to 7 ~ 8 mm.
2. Insert the wires into the male part of the connector according to the Mode you
are using. See below.
3. Use a flat-tip screwdriver to secure the wires. Tighten the screws to 6 in.-lbs.
4. Insert the plug into the receptacle on the amplifier.
5. Use a flat-tip screwdriver to secure the connector. Tighten the screws to 6 in.-lbs.
Stereo and Parallel Mode: Connect the wires as shown in — Figure 30, or as shown
by the solid wires in — Figure 32.
Bridge Mode: Connect the wires as shown in — Figure 31, or as shown by the
dashed wires in — Figure 32.
Stereo, Bi-amp, or Parallel Mode
— Figure 29 —
Stereo, Bi-amp, or Parallel Mode
— Figure 30 —
Bridge Mono Mode
— Figure 31 —
— Figure 32 —
Terminal Block Connector Wiring UL IEC
Wire range - 6 mm2
Solid wire (AWG) 28 – 10 -
Stranded wire (AWG/mm2 ) 28 – 10 -
Torque (lb.-in.) 6 -
Wire strip length 7 – 8 mm -
— Table 3 —

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Operation
AC Power Switch (AC Mains)
Make sure you connect the amplifier to the correct AC line voltage, as shown on the serial number label.
Connecting to the wrong line voltage is dangerous and may damage the amplifier (— Figure 33).
Before applying power, check all connections and turn the attenuation controls fully counter clockwise to
maximum attenuation.
One second of muting is normal when the amp is turned on or off (— Figure 34).
Attenuation Controls
The controls are marked with a scale indicating attenuation. Maximum attenuation is fully counter clockwise,
minimum attenuation is fully clockwise. he Attenuation controls are marked in numeric increments from ∞
to 0 (clockwise) indicating the amount of attenuation. Settings should normally be made within the lower
attenuation range. The range above 14 on the attenuation scale should not be used for normal program
levels, as the input headroom could be exceeded, but can be used for testing at reduced gain levels. At the
maximum attenuation setting (∞), the signal is completely cut off(— Figure 35).
LED Indicators
The green SIGNAL LED indicators light at approximately 0.1% of full power.
The red CLIP LED indicator flashes during overload (clipping). If the amplifier's
protection circuitry triggers protective muting, the signal and clip LEDs will not light.
If this occurs during use, see the Troubleshooting section on page 17.
Fan Cooling
The fan speed varies automatically
to maintain safe internal
temperatures. Keep the front and
rear vents clear to allow full air flow.
Hot air exhausts out the front of the
amp so it does not heat the interior
of the rack. Make sure that plenty
of cool air can enter the rack,
especially if there are other units
which exhaust hot air into it.
Safe Operating Levels
The amp's protective muting
system guards against excessive
internal temperatures. With normal
ventilation and 4 - to 8loads, the
amplifier will handle any signal level
including overdrive-but make sure that the speakers can handle the full power! However, lower load impedances and higher signal levels produce
more internal heating. Into 2loads, frequent or prolonged clipping (indicated by constant flashing of the red CLIP LED) may trigger protective
muting. Bridged mono mode doubles the output impedance of the amp; 4is the minimum load impedance. Heavy clipping may cause muting. If
this happens, see the Troubleshooting section on page 17.
— Figure 33 —
120 VAC 220-240 VAC
— Figure 34 —
— Figure 35 —
Model Maximum Voltage Gain
CMX 300Va 31.6 x (30 dB)
CMX 500Va 40 x (32 dB)
CMX 800Va 46 x (33 dB)
CMX 2000Va 31.6 x (30 dB)
— Table 4 —
— Figure 36 —
Cool air enters the
amplifier and rack.
Warm air exits the
amplifier and rack.
Rack

17
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Troubleshooting
Problem: No Sound
Indication: POWER indicator not lit
Check the AC plug. Also check the circuit breaker on the rear panel.
Confirm that the AC outlet works by plugging in another device. If too many amplifiers are used on one outlet, the building’s
circuit breaker may trip and shut off power.
An overload in Bridged Mono mode may cause the amplifier to click off for several seconds. Check the load impedance (4minimum), or
reduce signal level.
An amplifier which keeps shutting off may have a serious internal fault. Turn it off, remove AC
power, and have the amplifier serviced by a qualified technician.
Indication: SIGNAL LED responding to signal level
If the green SIGNAL indicators are lighting normally, the fault is somewhere between the amp
and the speaker. Check the speaker wiring for breaks. Try another speaker and cable.
Indication: SIGNAL LED not lit
If the green POWER indicator LED is lit and the fan is running, yet the signal LEDs indicate no
signal, check the input. Make sure the signal source is operating and try another input cable.
Connect the source to another channel or amplifier to confirm its operation.
Indication: CLIP LED flashing
If the red CLIP indicator flashes when signal is applied, the amplifier output may be shorted.
Check the speaker wiring for stray strands or breaks in the insulation.
Indication: CLIP LEDs bright and steady
The amplifier is in protective muting.
One second of muting is normal when the amp is turned on or off.
Overheating will cause protective muting. The fan will be running at full speed and the chassis
will be hot to the touch; sound should resume within a minute as the amplifier cools to a safe
operating temperature. Check for proper ventilation. If the fan isn’t running at all, the amplifier
requires servicing.
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, that cable or speaker is
shorted. Try another cable and speaker to locate the fault.
Indication: CLIP LED 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 attenuation controls at mid point so that
the source does not have to be overdriven.
— Figure 37 —
= lit
= blinking
= o
KEY
— Figure 38 —
POWER SIG SIGCLIP CLIP
— Figure 39 —
POWER SIG SIGCLIP CLIP
— Figure 40 —
POWER SIG SIGCLIP CLIP
— Figure 41 —
POWER SIG SIGCLIP CLIP
— Figure 42 —
POWER SIG SIGCLIP CLIP
— Figure 43 —
POWER SIG SIGCLIP CLIP
— Figure 44 —
POWER SIG SIGCLIP CLIP

18
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Problem: No channel separation
Check the switch settings on the back of the amplifier. Make sure the “Parallel Input” and “Bridge Mode” switches are OFF in dual-channel, bi-amp, or
stereo use where different signals go to each channel.
Make sure other equipment in the signal path, such as mixers, preamps, etc., are set for stereo, not mono.
Problem: Hum
Move cabling and signal sources to identify “hot spots” in the system. Cables with faulty shielding are a frequent entry point for hum.
Problem: Hiss
Unplug the amplifier input to confirm that the hiss is coming from the source or a device upstream; erratic or popping noises indicate an electronic
fault in the offending unit.
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.

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Specifications
CMX 300Va CMX 500Va CMX 800Va CMX 2000Va
Stereo Mode (both channels driven)
8/ FTC 20 Hz - 20 kHz / 0.1% THD
8/ EIA 1 KHZ / 0.1% THD
4/ FTC 20 HZ - 20 KHZ / 0.1% THD
4/ EIA 1 KHZ / 0.5% THD
4/ EIA 1 KHZ / 1% THD
2/ EIA 1 KHZ / 1% THD
70 V - Direct drive / EIA 1 kHz / 1% THD
100 V - Direct drive / EIA 1 kHz / 1% THD
185 W
200 W
280W
300 W
430 W
-
260 W
300 W
400 W
500 W
700 W
-
450 W
500 W
650 W
800 W
1200 W
400 W
1050 W
1100 W
1600 W
2000 W
2500 W
2500 W
1000 W
Bridge Mono Mode
8/ FTC 20 Hz - 20 kHz / 0.1%THD
8/ EIA 1 kHz / 0.1%THD
4/ EIA 1 kHz / 1%THD
70 V - Direct drive / EIA 1 kHz / 1% THD
100 V - Direct drive / EIA 1 kHz / 1% THD
140 V - Direct drive / EIA 1 kHz / 1% THD
530 W
600 W
830 W
600 W
-
800 W
900 W
1400 W
1200 W
600 W
1300 W
1500 W
2400 W
2000 W
2300 W
3200 W
3600 W
5000 W
3600 W
5000 W
Distortion (SMPTE-IM) < 0.02% < 0.01% < 0.01% < 0.01%
Signal to Noise (20 Hz – 20 kHz) 8> -100 dB
Input Sensitivity 81.15 V (+3.4 dBu) 1.15 V (+3.4 dBu) 1.23 V (+4.0 dBu) 1.42 V (+5.3 dBu)
Voltage Gain (8) 30 dB 32 dB 33 dB 36 dB
Output Circuitry Class AB Class AB 2-tier Class H 3-tier Class H
Power Requirements
Typical, 1/8 power, pink noise at 4
120 VAC
230 VAC
Severe, 1/3 power pink noise at 4
120 VAC
230 VAC
4.4 A
2.2 A
6.6 A
3.3 A
5.4 A
2.7 A
9.6 A
4.8 A
6.3 A
3.2 A
15.6 A
7.8 A
13.9 A
7 A
26.9 A
13.5 A
Frequency Response 20 Hz – 20 kHz, +0, -1 dB -3 dB points:
5 Hz and 50 kHz (LF filter bypassed / 8)
20 Hz – 20 kHz, +/- 1 dB dB -3 dB points:
5 Hz and 50 kHz (LF filter bypassed / 8)
Damping Factor > 300 at 8
Input Impedance () 10 kunbalanced / 20 kbalanced
Input Clipping 10 Vrms (+22 dBu) 6.4 Vrms (+18 dBu)
Cooling Continuously variable speed fan, back-to-front air flow
Connectors (each channel) Input: Active balanced; barrier strip, XLR and ¼" (6.3 mm) TRS tip and XLR (pin 2 positive)
Output: Detachable terminal block and NL4
Controls Front: AC Switch, Channel 1 and Channel 2 attenuation knobs
Rear: 10-position DIP switch
Indicators Power-on: Green LED / Signal: Green LED (1 per channel) / Clip: Red LED (1 per channel)
Amplifier Protection Stable into reactive or mismatched loads
Load Protection On/off muting, AC Coupling On/off muting, triac crowbar on each channel
Dimensions (HWD)
Inches
Millimeters
2RU
3.5 x 19 x 15
89 x 483 x 381
3RU
5.25 x 19 x 15
133 x 483 x 381
Weight
Net
Shipping
35 lb (15.9 kg)
41 lb (18.6 kg)
40 lb (18.2 kg)
46 lb (20.9 kg)
44.5 lb (20.2 kg)
50.5 lb (23.0) kg)
75 lb (34 kg)
87 lb (39.5 kg)

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Mailing Address:
QSC Audio Products, LLC
1675 MacArthur Boulevard
Costa Mesa, CA 92626-1468 USA
Telephone Numbers:
Main Number: [phone]
Sales & Marketing: [phone] or toll free (USA only) [phone]
Customer Service: [phone] or toll free (USA only) [phone]
Facsimile Numbers:
Sales & Marketing FAX: [phone]
Customer Service FAX: [phone]
World Wide Web:
www.qsc.com
E-mail:
[email protected]
[email protected]
© 2013 QSC Audio Products, LLC. All rights reserved. QSC™ and the QSC logo are registered trademarks of QSC Audio Products, LLC.
All other trademarks are the property of their respective owners. Patents pending.