QSC Audio Stereo Amplifier TD 000271 01 User Guide

TM  
GX POWER AMPLIFIER SERIES  
User Manual  
GX3 300 watts per channel at 8 ohms  
GX5 500 watts per channel at 8 ohms  
EN  
TD-000271-01 REV. A  
*TD-000271-01*  
 
3
GX POWER AMPLIFIER SERIES  
Professional Power Amplifiers  
WELCOME  
Thank you for purchasing a QSC Audio amplifier. The GX Series is  
the latest in a long line of hard-working, low cost amplifiers, designed  
to produce the best possible results for a wide range of users. In  
most cases, you can plug and play with no surprises, but for best  
results, we recommend you review the enclosed user guide.  
UNPACKING  
EN  
Confirm that the amplifier has no visible shipping damage. Confirm  
that amplifier has the correct AC cord and voltage rating for your  
region (See rear panel, Serial Number plate). It is best to keep the  
carton in case the amplifier needs to be returned, at least until it has  
been tested.  
FEATURES  
Power levels matched to the most popular speakers used by  
entertainers.  
Optimized for maximum real-world headroom into 4Ω and  
8Ω speaker systems.  
SUPPORT AND SERVICE  
Inputs: XLR, 1/4” TRS and phono input connectors for  
compatibility with any source.  
QSC Audio Products maintains a world-wide network of distributors  
and service centers. These local agencies will be able to answer your  
questions and take care of any problems.  
Outputs: Speakon® combo accepts 1/4” (TS) plugs or  
Speakon 2-pole and 4-pole plugs (connects 2 poles only).  
Binding posts support all other speaker wiring systems.  
QSC WEBSITE  
supported in multiple languages. Visit frequently for new  
announcements, typical questions, and other user information.  
Minimum depth chassis (only 10.1” / 257 mm) fits in  
compact, inexpensive effects racks.  
Light weight – less than 26 lbs (12.5 kg).  
IMPORTANT SAFETY PRECAUTIONS  
QSC products are designed for safe operation, and have been  
certified by recognized product safety agencies to meet all normal  
standards for this type of product. However, dangerous voltages  
and power levels exist within the covers of this amplifier. The user  
is requested to study the precautions in this manual. If the product  
has been dropped, dented, soaked, or appears to have loose parts  
inside, the risk of shock is increased. Unplug the AC cord, and take  
the product to qualified service personnel for inspection and repairs.  
Detented gain controls for precise setting and matching of  
sensitivity.  
GuardRail automatically protects the amplifier and  
loudspeakers from damage due to temperature rise or  
overdrive without shutting down the show.  
Front panel LEDs monitor Power, Signal and Clipping.  
Subwoofer / Satellite crossover built-in.  
POWER RATINGS  
Watts at 0.1% clipping, both channels driven  
Model  
GX3  
8 ohms  
300  
4 ohms  
4ꢀ5  
ꢀ ohms*  
ꢀ00  
GX5  
500  
700  
350  
*NOTE: 2-ohm loading is not recommended for high power use.  
To avoid protective limiting, use only at low levels.  
 
4
FRONT PANEL FEATURES  
MODEL NUMBER  
The GX3 and GX5 power  
ratings are shown in the  
Specifications page.  
ON-OFF SWITCH  
Move the rocker switch up to turn on the amplifier.  
The blue PWR LED will turn on immediately.  
The red CLIP LEDs may trigger for 1-2 seconds until the amp  
has completed its turn-on cycle. If no lights come on, check the  
power cord and the AC reset on the rear panel.  
COOLING VENTS  
The internal fan draws air in from the left side,  
and exhausts on the right side. Keep vents clear.  
The fan speeds up in response to heavy use.  
EN  
DIMENSIONS  
10.1  
Inches (cm)  
(25.7)  
17.0  
(43.2)  
9.0  
(22.9)  
19.0  
(48.3)  
3.5  
(8.9)  
 
5
GAIN CONTROLS, CH1, CH2  
The markings show attenuation in dB. For normal  
use, keep the control in the upper half of its range  
(less than 10 dB of attenuation). If set below half,  
the source may overload before the amplifier  
reaches full power.  
RACK MOUNTING  
Fits standard 19-inch rack, 2RU.  
Accepts #10 or 6 mm screws,  
as determined by the rack rails.  
Add rear support to prevent  
damage in portable rigs.  
EN  
RED CLIP LEDS  
Red flashing indicates the amp is being overdriven. Heavy overdrive triggers internal gain  
reduction, to reduce overload distortion. Normal gain will resume after the signal level returns to  
normal. See Troubleshooting if the red LED remains on continuously.  
GREEN SIGNAL LEDS  
The green LED starts flashing on soft signals (-35 dB), and changes to steady green as the  
signal level increases.  
BLUE POWER LED  
The blue PWR (POWER) LED indicates that the AC switch is on, and the amp is receiving  
power. Within two seconds, it is ready to use.  
ALTERNATE GAIN MARKING  
When the CROSSOVER switch is active (see rear panel),  
LF (CH 1) controls low frequencies (subwoofer),  
HF (CH 2) controls the high frequencies (mid-high box).  
 
6
REAR PANEL FEATURES  
CROSSOVER SWITCH  
EXHAUST VENT  
Keep vent clear. Install in  
open-back rack.  
CROSSOVER POSITION  
Splits a full-range signal to drive a subwoofer and top box.  
CH 1 receives the lows, from 20-100Hz, for the subwoofer.  
CH 2 receives 100Hz to 20kHz, to power a full range speaker.  
When using CROSSOVER mode, connect signal to CH 1 only.  
Use the two Gain controls to balance the LF and HF signals  
(see Front Panel).  
FULL RANGE POSITION  
For normal, 2-channel use with all inputs active.  
The crossover is bypassed.  
EN  
REAR EAR MOUNTING  
INPUT CONNECTIONS  
Rear ears designed for protecting the  
rear connector wire dressing and  
supporting the amplifier in a rack. A rear  
rack support mounting kit (model FG-  
000031-00 pack of two) is available from  
QSC Technical Services Group.  
BALANCED XLR INPUTS  
Pin 2 Positive, Pin 3 Negative, Pin 1 Shield (Ground).  
Recommended for long or short runs, either fixed or  
frequently changed. Each channel’s XLR and TRS jacks  
are connected internally, and provide feed thru  
to the other connector.  
BALANCED 1/4-INCH TRS INPUTS  
Tip positive, Ring Negative, Sleeve Shield (Ground).  
Recommended for long or short runs that are frequently  
changed.  
UNBALANCED 1/4-INCH TS INPUTS  
Accepts unbalanced 1/4-inch plugs for short runs.  
Tip positive, Sleeve Shield (Ground).  
UNBALANCED PHONO INPUTS  
Tip Positive, Barrel Shield (Ground). Recommended  
for semi-permanent connections to nearby sources,  
within the same rack. NOTE: when using these  
inputs, the TRS or XLR inputs should not be used.  
 
7
AC BREAKER RESET  
If the amplifier shuts off after a long burst of power,  
turn off the AC switch and check the circuit breaker.  
The button can be pressed back in after a 30 second  
cool-down period. If the breaker trips repeatedly,  
the amplifier may need servicing.  
SERIAL NUMBER AND RATINGS  
The rated AC voltage and output power  
is shown on the serial number plate.  
Record the serial number in a safe place.  
EN  
AC INLET  
SPEAKER CONNECTIONS  
BINDING POSTS  
Accepts banana plugs  
(not permitted in CE regions).  
Bare wires or terminals may be  
inserted into the side holes.  
1/4-INCH CONNECTORS  
Insert plug into the center of  
the Speakon-Combo jack.  
Use only heavy duty speaker cables.  
SPEAKON CABLES (2 wire type):  
Insert and turn until the connector clicks.  
Use the thumb latch or locking ring  
to release the plug.  
 
8
SYSTEM HOOKUP EXAMPLES  
INPUT CONNECTIONS  
SPEAKER CONNECTIONS  
8 OR 4 OHM  
XLR  
MIXER  
SIGNAL LEVEL SOURCE  
SPEAKON  
SET TO FULL RANGE  
SET TO FULL RANGE  
SET TO FULL RANGE  
¼
MIXER  
EN  
¼
SIGNAL LEVEL SOURCE  
WIRE  
PHONO  
MIXER  
SIGNAL LEVEL SOURCE  
BANANA JACKS  
One 4-OHM speaker, or two 8-OHMspeakers, may be connected to each channel.  
If speakers have pass through jacks, do not put more than two in a chain.  
CONNECTION MULTIPLE SPEAKERS  
To connect two speakers to one amplifier channel,  
connect one speaker with Speakon or 1/4 –inch jack,  
and connect the other speaker with a banana plug  
or wires to the binding posts.  
8 OHM  
8 OHM  
8 OHM  
8 OHM  
It is also possible to use banana plug for one speaker,  
and binding post wires for the other speaker.  
Second speaker  
First speaker  
4 OHM  
8 OHM  
4 OHM  
8 OHM  
Speakon  
and wires to  
the binding posts.  
Second speaker  
1/4 –inch jack,  
And wires to the  
First speaker  
4 OHM  
binding posts.  
4 OHM  
4 OHM  
4 OHM  
Second speaker  
First speaker  
banana plug  
and binding post  
 
SYSTEM HOOKUP EXAMPLES  
SUBWOOFER AND TOP BOX  
Move the CROSSOVER switch to  
the CROSSOVER position.  
Connect a single source, into the  
Ch 1 input.  
Connect a subwoofer to the  
Ch 1 output and connect a  
2-way to box to the Ch 2 output.  
8 OR 4 OHM  
INPUT  
TOP  
SET TO CROSSOVER  
8 OR 4 OHM  
SUB  
8 OHM  
8 OHM  
POWERING HOUSE AND MONITOR SPEAKERS  
MAIN  
MAIN  
EN  
Set the CROSSOVER switch  
to the FULL RANGE position.  
Use a mixer with Main and  
Monitor outputs. Connect cables  
into Ch 1 and 2 respectively.  
Connect Ch 1 output to  
two large speakers.  
Connect Ch 2 output to  
two floor wedges.  
SET TO FULL RANGE  
4 OR  
8 OHM  
4 OR  
8 OHM  
STEREO PLAYBACK  
OR  
Set the CROSSOVER switch in the  
FULL RANGE position. Connect a  
Left / Right signal source to channel 1  
and channel 2 respectively using  
XLR, TRS or PHONO connectors.  
Connect a speaker to each channel  
using SPEAKON, ¼’ PHONE,  
L
R
BANANA JACKS or WIRE.  
SET TO FULL RANGE  
L1  
USING BOTH CHANNELS FOR THE SAME  
L2  
4 OR  
4 OR  
8 OHM  
Move the CROSSOVER switch to the  
FULL RANGE position. Hook up a single source  
using Ch 1 XLR input. Install a RTS jumper  
going between Ch1 and Ch2.  
8 OHM  
Connect a speaker to each channel.  
Each speaker ahs its own gain  
adjustment on the front panel.  
DO NOT connect both channels  
Into the same speaker.  
SET TO FULL RANGE  
FULL RANGE  
DO NOT connect both  
Channels to the same speaker.  
RTS jumper  
between  
CH1 and CHꢀ  
 
10  
TROUBLESHOOTING  
NO POWER, NO LIGHTS, NO FAN  
NO SOUND, WITH BLUE LED ONLY, NO GREEN OR  
RED LED  
Confirm that the Gain controls are turned up. Confirm that  
the input cables are correctly installed at both ends. If using  
1/4-inch speaker cables, do not confuse with input cables.  
Confirm that the source is active. If necessary, try another  
source, or connect another amplifier to the existing source.  
Confirm that the AC cord is fully seated and connected to a  
live outlet. Check the AC source by trying another device  
such as a lamp. Check the BREAKER on the back of the  
amplifier by pushing in the button. If the breaker trips off  
quickly, the amplifier needs servicing.  
AMPLIFIER LOSES VOLUME  
If the amplifier is worked too hard, GuardRail™ will  
reduce volume to prevent thermal muting. The fan should be  
running at full speed. Reduce input signal somewhat and the  
amp should return to normal gain within 1-2 minutes. If the  
amp feels hot and the fan is not running, it needs to be  
serviced.  
NO SOUND, BUT THE GREEN LED IS RESPONDING  
The green LED indicates the amp is producing a signal, so  
sound should be heard if the speaker is connected. Check  
the speaker connections at both ends, and try a different  
speaker.  
EN  
NO SOUND, RED LED ON  
CHANNEL 1 PRODUCES DEEP BASS ONLY.  
Check the position of the CROSSOVER switch on the rear  
panel. Set on FULL RANGE for normal, independent use of  
each channel.  
The amp mutes briefly when turned on and off to prevent  
thumps. If the amp overheats severely, it will mute until it cools off.  
The fan will be running at full speed, and sound should  
resume in less than a minute. If the amp feels hot and the fan  
is not running, it needs to be serviced.  
CHANNEL ꢀ INPUT SEEMS DEAD.  
Check the position of the CROSSOVER switch on the rear  
panel. Set on FULL RANGE for normal, independent use of  
each channel.  
BACKGROUND HUM  
Balanced XLR or TRS cables are better for long runs. Hum can be a  
problem when connecting to TV-cable rigs, since the TV cable often  
creates a ground conflict. Request or install a TV-cable isolator to  
reduce this problem.  
AMPLIFIER SOUNDS DISTORTED.  
If the red CLIP LED is flashing, the amplifier is being played  
beyond its normal rated power. GuardRail™ circuitry will reduce  
volume somewhat to prevent severe overdrive, but if the input  
signal is further increased, the limiter can be overridden, with  
increased distortion.  
Hum can also occur earlier in the signal chain, depending on the  
types of connections. It often helps to plug everything into the same  
AC strip, if the total power consumption is not excessive.  
As a last resort, mild hum can sometimes be reduced by  
lowering the amp gain, and increasing the source gain to  
compensate, but you must ensure that the source can deliver  
the extra volume without overload distortion. If this does not  
reduce hum, it is coming from the source.  
If the speakers or speaker cables are shorted or defective,  
the amplifier may distort at lower-than-normal levels, with  
increased flashing of the red CLIP LED. This should be  
checked by trying an alternate speaker and cable.  
If too many speakers are connected to each channel  
(impedance below 4 ohms), the amp will overload more  
easily and will probably run hot.  
AMPLIFIER NEEDS SERVICING  
The following conditions indicate possible unsafe conditions  
that require service before using. If observed, unplug the AC  
cord from the wall and when safe, remove the amp for  
servicing.  
If the sound is distorted or garbled without flashing the red  
CLIP LED, the distortion is not occurring inside the amplifier.  
Either the speaker is bad or the input signal is distorted.  
• Confirm that the speaker is OK by trying a different unit.  
• Input overload can occur if the amplifier Gain controls are set too  
low, and the input source is overdriven to compensate Reduce the  
source volume until the distortion clears up, and increase amp Gain  
to reach the desired level. It is generally desireable to keep the  
amp gains at or near their full, clockwise, position.  
• If the amplifier emits smoke or burning smells  
• If the case is severely dented or deformed  
• If the amplifier is soaked with any fluid  
• If internal parts sound loose  
• If the AC breaker trips when power is applied  
• If the amplifier is dropped, carefully inspect for damage or  
loose parts before attempting to use.  
• Check all input connections. Do not plug two different sources into  
the same channel. Use a mixer to blend sources.  
 
11  
SPECIFICATIONS  
GX3  
GX5  
SPECIFICATION SUBJECT TO CHANGE WITHOUT NOTICE.  
OUTPUT POWER, 1 kHz, 0.1 % clipping  
8Ω, both channels driven  
8Ω, single channel driven  
4Ω, both channels driven  
4Ω, single channel driven  
2Ω, both channels driven, 1% clipping  
SIGNAL TO NOISE (20 Hz – 20 kHz)  
INPUT SENSITIVITy  
300 W  
350 W  
425 W  
500 W  
200 W  
100 dB  
1.2 Vrms  
32.2 dB  
Class B  
6.3 A  
500 W  
600 W  
700 W  
850 W  
350 W  
EN  
VOLTAGE GAIN AT 8Ω  
34.4 dB  
2-tier Class H  
6 A  
OUTPUT CIRCUITRy  
POWER REQUIREMENTS (1/8 power, pink noise  
at 4Ω 120 V AC)  
DISTORTION (1 dB below rated power, 20 – 20 kHz)  
8Ω, less than 0.05%  
4Ω, less than 0.1%  
FREQUENCy RESPONSE  
DyNAMIC HEADROOM, 4Ω  
DAMPING FACTOR  
20 – 20kHz, +0, -1dB  
2dB  
100  
INPUT IMPEDANCE  
Greater than 20K ohms (balanced or unbalanced)  
+24 dB (16 Vrms)  
MAXIMUM INPUT LEVEL  
INPUT CONNECTORS, each channel  
3-pin XLR and 1/4” TRS, balanced, parallel  
Phono, unbalanced  
OUTPUT CONNECTORS, each channel  
AMPLIFIER AND LOAD PROTECTION  
Speakon®, 1/4”, Binding Posts  
Short circuit, open circuit, thermal, RF protection  
Load protected against DC faults  
CONTROLS AND INDICATORS, FRONT PANEL  
Gain controls, 21 detents  
Red Clip LEDs, proportional, 0.1% THD threshold.  
Green Signal LEDs, threshold -35 dB  
Blue Power LED, AC-on.  
CONTROLS, REAR PANEL  
Full Range / Crossover switch  
100 Hz, 3rd order LP (sub), 2nd order HP (top).  
DIMENSIONS (HWD)  
WEIGHT – Shipping / Net  
AGENCy APPROVALS  
3.5” (2RU) x 19” x 10.1” (89 mm x 483 mm x 257 mm)  
30 / 25 lbs (13.5 / 11.5 kg)  
31 / 26 lbs (14 / 12 kg)  
UL, CE, RoHS / WEEE compliant  
AC POWER CONSUMPTION 1/8 power, ohms (AC Current and Heating, 120Vac)  
GX3  
GX5  
Operating Condition  
Idle  
AC amps  
0.2  
BTU / hr  
44  
904  
1160  
1109  
1515  
2105  
2297  
AC amps  
0.3  
BTU / hr  
60  
734  
1456  
1891  
1160  
2162  
3754  
8 + 8 ohms, 1/8 power (1)  
8 + 8 ohms, 1/3 power (2)  
8 + 8 ohms, full power (3)  
4 + 4 ohms, 1/8 power (1)  
4 + 4 ohms, 1/3 power (2)  
4 + 4 ohms, full power (3)  
4.1  
6.1  
9.75  
6.3  
9.4  
3.3  
8.5  
16.2  
5.8  
11.2  
24.5  
15.0  
(1) 1/8 power represents typical operating conditions. (2) 1/3 power represents peak program levels.  
(3) Full power is breaker limited to short periods. (4) For 230V, multiply AC current by 0.5. For 100V, multiply AC current by 1.25.  
 
WARRANTY  
(USA only; other countries, see your dealer or distributor)  
Disclaimer  
QSC Audio Products, Inc. is not liable for any damage to amplifiers or any other equipment that is caused by negligence or  
improper installation and/or use of this loudspeaker product.  
QSC Audio Products 3 Year Limited Warranty  
QSC Audio Products, Inc. ( QSC ) guarantees its products to be free from defective material and / or workmanship for a period  
of three (3) years from date of sale, and will replace defective parts and repair malfunctioning products under this warranty when  
the defect occurs under normal installation and use - provided the unit is returned to our factory or one of our authorized service  
stations via prepaid transportation with a copy of proof of purchase (i.e., sales receipt). This warranty provides that the examination  
of the return product must indicate, in our judgment, a manufacturing defect. This warranty does not extend to any product which  
has been subjected to misuse, neglect, accident, improper installation, or where the date code has been removed or defaced.  
QSC shall not be liable for incidental and/or consequential damages. This warranty gives you specific legal rights. This limited  
warranty is freely transferable during the term of the warranty period. Customer may have additional rights, which vary from state  
to state.  
EN  
In the event that this product was manufactured for export and sale outside of the United States or its territories, then this  
limited warranty shall not apply. Removal of the serial number on this product, or purchase of this product from an unauthorized  
dealer, will void this limited warranty. Periodically, this warranty is updated. To obtain the most recent version of QSC’s warranty  
How to Contact QSC Audio Products  
Mailing address:  
QSC Audio Products, Inc.  
1675 MacArthur Boulevard  
Costa Mesa, CA 92626-1468 USA  
Telephone Numbers:  
Main Number (714) 754-6175  
Sales & Marketing (714) 957-7100 or toll free (USA only) (800) 854-4079  
Customer Service (714) 957-7150 or toll free (USA only) (800) 772-2834  
Facsimile Numbers:  
Sales & Marketing FAX (714) 754-6174  
Customer Service FAX (714) 754-6173  
World Wide Web:  
TM  
QSC Audio Products, Inc. 1675 MacArthur Boulevard Costa Mesa, California 92626 USA  
©2007 “QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office.  
 

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