QSC Audio Stereo Amplifier MX2000a User Guide

MXa Series  
MX 1000a  
MX 1500a  
MX 2000a  
MX 3000a  
®
*TD-000026-00*  
Rev. B  
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I. WARNING NOTICES  
CAUTION  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
SPEAKER DAMAGE  
CAUTION: To reduce the rish of electric shock, do not remove  
the cover. No user-serviceable parts inside. Refer servicing to  
qualified service personnel.  
The MXa Series amplifiers are among the most powerful  
professional amplifiers available and is capable of pro-  
ducing much more power than many loudspeakers can  
handle. It is the users responsibility to use suitable  
speakers with the amplifier and to use them in a sensible  
way that will not cause damage.  
WARNING: To prevent fire or electric shock, do not expose this  
equipment to rain or moisture.  
QSC will not be responsible for blown speakers. Consult  
the speaker manufacturer for power-handling recom-  
mendations.  
AVIS  
EitherchanneloftheMX3000aamplifierhasspecialclip-  
limitingprotectioncircuitrythatreducesthesignallevelat  
the onset of heavy clipping. This not only allows the  
amplifiertooperateatahighaveragepowerlevelwithout  
audible distortion occurring, but it also prevents the  
speakersbeing destroyed by excessive clipping. How-  
ever, if the amplifier is operating normally and your  
speakers fail anyway, it is virtually certain that they could  
not handle the high power, despite the lack of clipping.  
RISQUE DE CHOC  
ÉLECTRIQUE  
NE PAS OUVRIR  
ATTENTION: Pour eviter les risques de choc électrique, ne pas  
enlever le courvercle. Aucun entretien de pièces intérieures  
par lusager. Confier lentretien au personnel qualifié.  
AVIS: Pour eviter les risques dincendie ou délectrocution,  
nexposez pas cet article à la pluie ou a lhumidité.  
Even if you reduce the gain using the amplifiers front  
panel attenuator controls, it is still possible to reach full  
output power if the input signal level is high enough.  
A single high-power crescendo can blow high-frequency  
driversalmostinstantaneously,whilelow-frequencydriv-  
ers can usually withstand very high, continuous power  
levels for a few seconds before they fail. Reduce power  
immediately if you hear any speaker bottoming out”—  
harsh pops or cracking distortion that indicate that the  
speaker voice coil or diaphragm is striking the magnet  
assembly.  
VORSICHT  
GEFAHR EINES  
ELEKTRISCHEN SCHLAGES.  
NICHT ÖFFNEN!  
VORSICHT: Um das Risiko eines elektrischen Schlages zu  
vermindern, Abdeckung nicht entfernen! Keine Benutzer  
Wartungsteile im Innern. Wartung nur durch qualifiertes  
Wartungspersonal.  
QSC recommends that you use amplifiers of this power  
range for more headroom (cleaner sound) rather than for  
increased volume.  
WARNUNG: Zur vermeidung von Feuer oder elektrischen  
Schlägen, das Gerät nicht mit Regen oder Feuchtigkeit in  
Berührung bringen!  
SPEAKER OUTPUT SHOCK HAZARD  
An MXa amplifier is capable of producing hazardous  
output voltages. To avoid electrical shock, do not touch  
any exposed speaker wiring while the amplifier is operat-  
ing.  
SAFEGUARDS  
Electrical energy can perform many useful functions. This unit has  
been engineered and manufactured to assure your personal safety.  
Improperusecanresultinpotentialelectricalshockorfirehazards.  
Inordernottodefeatthesafeguards,observethefollowinginstruc-  
tions for its installation, use and servicing.  
RACK MOUNTING PRECAUTIONS  
In portable racks, to avoid damage to either the amplifier  
mountingearsorthemountingrails, supporttheamplifier  
at all four corners. Contact the QSC Customer Service  
Department to order rear support brackets.  
PRECAUTIONS  
L’énergie électrique peut remplir de nombreuses fonctions utiles.  
Cet appariel a été conçu et réalisé pour assurer une sécurité  
personnelle entiére. Une utilisation impropre peut entraîner des  
risques d’électrocution ou d’incendie. Dans le but de ne pas rendre  
inutiles les mesures de sécurité, bien observer les instructions  
suivantes pour l’installation, l’utilisation et l’entretien de l’appareil.  
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Theamplifiersrequirearackdepthof18inches(45.7cm)  
to clear the rear support ears. Allow some additional  
clearance for input and output connectors at the rear  
panel, which is 16.9 inches (42.9 cm) behind the plane of  
the front mounting rails. The built-in cooling fan draws air  
in at the rear of the chassis and exhausts it through vents  
in the front panel. The flow-through cooling scheme  
allows you to rack-mount the amplifiers one atop the  
other, with no clearance necessary in between. This  
mounting technique also helps support the weight of the  
upper amplifiers.  
II. OVERALL DESCRIPTION  
The MXa Series from QSC comprises four high-effi-  
ciency professional power amplifier models, each with  
two independent channels. The MX 1000a, MX 1500a,  
and MX 2000a, can deliver, respectively, 275, 400, and  
475 watts into 8-ohm loads, and 400, 600, and 725 watts  
into 4-ohm loads  
Either channel of the MX 3000a is capable of delivering  
850 watts into 8-ohm loads, 1300 watts into 4-ohm loads,  
or more than 1600 watts into 2 ohms.  
TheMXaSeriesderivesmuchofitsdesignfromourhigh-  
end EX Series amplifiers. They are engineered for stabil-  
ity and exceptional reliability, with protection for open or  
short circuits and mismatched loads. To protect your  
loudspeakers, the outputs mute during turn-on and turn-  
off, and also in the event of a DC fault. All protection  
circuitry automatically resets to normal when conditions  
assure safe operation.  
Each channel has its own transformer secondary (MX  
1000a and MX 1500a) or power transformer (MX 2000a  
and MX 3000a) and bipolar multi-rail power supply. The  
power transformers are mounted in the front of the  
amplifier chassis, as close to the front mounting rails as  
possible; this keeps the units center of gravity forward to  
minimize the twisting force on the front mounting ears.  
Still, the amplifier should be supported at all four corners,  
especially if it is in a portable rack such as in touring or  
mobile applications.  
The amplifiers feature thermal protection. The MX 3000a  
features a variable-speed fan, which responds continu-  
ously to the cooling needs to minimize noise and dust  
build-up, and a thermal limiter that reduces gain up to 15  
dB if the amplifier overheats above 80˚ C. The other  
models have a two-speed fan. If an MXa amplifier over-  
heats to 85˚ C or higher, a protection circuit mutes the  
output.  
The MX 1000a and MX 1500a are both two rack spaces  
high and weigh 19 kg (42 lb). The MX 2000a and MX  
3000a occupy three rack spaces. The MX 2000a weighs  
24.5 kg (54 lb), and the MX 3000a weighs 31 kg (69 lb).  
GAIN 1  
10  
GAIN 2  
10  
ON  
12  
8
12  
8
PROT CLIP  
SIG PWR  
PWR SIG  
CLIP PROT  
14  
18  
24  
6
14  
18  
24  
6
4
4
2
2
OFF  
0
0
MX 1500a  
Professional Stereo Amplifier  
- dB  
- dB  
Figure 1: QSC MX 1500a Front Panel (identical to the MX 1000a)  
GAIN 1  
10  
GAIN 2  
ON  
10  
12  
8
12  
8
PROT CLIP  
SIG PWR  
PWR SIG  
CLIP PROT  
14  
18  
24  
6
14  
18  
24  
6
4
4
2
2
OFF  
0
0
MX 2000a  
Dual Monaural Amplifier  
- dB  
- dB  
Figure 2: QSC MX 2000a Front Panel (identical to the MX 3000a)  
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MX 1500a INPUTS  
III. INPUTS  
The amplifiers input sensitivity is 1.07 volt rms; at this  
signal level and any attenuators set for full gain, the  
amplifier will produce full rated power350 watts, 20Hz-  
20kHz,0.1%THDintoan8-ohmload.Theinputimped-  
ance is 20 kilohm balanced and 10 kilohm unbalanced,  
typical of QSC amplifiers.  
An MXa amplifier features balanced inputs, connected  
via barrier strip terminals or 1/4(6.3 mm) tip/ring/sleeve  
phone jacks. The tip of the input jack is wired for nega-  
tiveorinvertedpolarity,whiletheringisthenon-inverting  
input. Thus, ifthevoltageatthetipispositivewithrespect  
to that at the ring, the amplifier channel will produce a  
negative voltage at its output.  
For use with unbalanced signals, connect the unused  
terminal to ground to avoid a reduction in gain caused by  
a floating input; use a two-conductor (tip/sleeve) plug, or  
connect a jumper between the inverting input terminals  
on the barrier strip and their adjacent ground terminal.  
MX 2000a INPUTS  
The amplifiers input sensitivity is 1.05 volt rms; at this  
signal level and any attenuators set for full gain, the  
amplifier will produce full rated power450 watts, 20Hz-  
20kHz,0.1%THDintoan8-ohmload.Theinputimped-  
ance is 20 kilohm balanced and 10 kilohm unbalanced,  
typical of QSC amplifiers.  
MX 1000a INPUTS  
The amplifiers input sensitivity is 1.1 volt rms; at this  
signal level and input attenuators set for full gain, the  
amplifier will produce full rated power250 watts, 20Hz-  
20kHz,0.1%THDintoan8-ohmload.Theinputimped-  
ance is 20 kilohm balanced and 10 kilohm unbalanced,  
typical of QSC amplifiers.  
MX 3000a INPUTS  
The amplifiers input sensitivity is 1 volt rms; at this signal  
levelandanyattenuatorssetforfullgain,theamplifierwill  
produce full rated power800 watts, 20Hz-20kHz, 0.1%  
THDinto an 8-ohm load. The input impedance is 20  
kilohm balanced and 10 kilohm unbalanced, typical of  
QSC amplifiers.  
An MXa Series amplifier features a Level I Open Input  
Architecture slot. See Section 2 for more information  
about Open Input Architecture.  
BRIDGED MONO  
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WARNING:TO REDUCE THE RISK OF FIRE  
OR ELECTRIC SHOCK, DO NOT EXPOSE THIS  
EQUIPMENT TO RAIN OR MOSTURE.  
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CHANNEL 2  
CHANNEL 1  
AVIS  
RISQUE DE CHOC ELECTRIQUE  
NE PAS OUVRIR  
CAUTION  
RISK OF ELECTRIC SHOCK  
DO NOT OPEN  
TIP NEG RING POS  
SLEEVE GND  
TIP NEG RING POS  
SLEEVE GND  
CLASS 2 WIRING  
STEREO 4 OHM MIN/CH.  
CH 2 INPUT CH 1  
BRIDGED MONO 8 OHM MIN. CLASS 1 WIRING MUST BE USED  
BRIDGED MONO OPERATION: PLACE BRIDGING SWITCH ON INPUT PANEL  
TO BRIDGED POSITION. CONNECT INPUT SIGNAL TO CH 1 ONLY.  
CONNECT SPKR (+) TO CH 1 (+) OUTPUT. CONNECT SPEAKER () TO  
CH 2 (+) OUTPUT. SET CH 2 GAIN FULLY CLOCKWISE AND REGULATE  
LEVEL WITH CH 1 GAIN CONTROL.  
STEREO  
PARALLEL  
BRIDGE  
CH 2  
CH 1  
GND  
+
+
Figure 3: QSC MX 1500a Back Panel (identical to the MX 1000a)  
BRIDGED MONO  
WARNING:TO REDUCE THE RISK OF FIRE  
OR ELECTRIC SHOCK, DO NOT EXPOSE THIS  
EQUIPMENT TO RAIN OR MOSTURE.  
+
+
CHANNEL 2  
CHANNEL 1  
TIP NEG RING POS  
SLEEVE GND  
TIP NEG RING POS  
SLEEVE GND  
CH 2 INPUT CH 1  
CLASS 2 WIRING  
STEREO 4 OHM MIN/CH.  
STEREO  
BRIDGED MONO 8 OHM MIN. CLASS 1 WIRING MUST BE USED  
BRIDGED MONO OPERATION: PLACE BRIDGING SWITCH ON INPUT PANEL  
TO BRIDGED POSITION. CONNECT INPUT SIGNAL TO CH 1 ONLY.  
CONNECT SPKR (+) TO CH 1 (+) OUTPUT. CONNECT SPEAKER () TO  
CH 2 (+) OUTPUT. SET CH 2 GAIN FULLY CLOCKWISE AND REGULATE  
LEVEL WITH CH 1 GAIN CONTROL.  
PARALLEL  
BRIDGE  
CH 2  
CH 1  
GND  
+
+
AVIS  
RISQUE DE CHOC ELECTRIQUE  
NE PAS OUVRIR  
CAUTION  
RISK OF ELECTRIC SHOCK  
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DO NOT OPEN  
Figure 4: QSC MX 2000a Back Panel (identical to the MX 3000a)  
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IV. OUTPUTS  
V. OPERATIONS  
When the amplifier is first turned on, the red PROTLED  
on each channel will light for about three seconds, during  
which the output relays will stay open to mute the speak-  
ers. After the turn-on muting interval, the PROTLEDs  
turn off, the green PWRLEDs light, and the output  
relays close to enable the speaker outputs. Even during  
themutinginterval, theyellowSIGandredCLIPLEDs  
operate normally if there is a signal present. If the CLIP”  
LED is on while the amplifier is muted, cut the gain back  
immediatelytoavoidafull-powerblastofsoundwhenthe  
output relays close. (Whenever it is practical, at turn-on  
youshouldhavetheattenuatorsallthewaydowntoavoid  
this situation.) If a channel stays muted with PROTlit,  
or if its SIGor CLIPindicators light up when the gain  
is turned all the way down, it may be defective; see the  
troubleshooting segment for more information.  
Four touch-proofbinding postsone pair per chan-  
nelon the rear panel allow speaker cable connections  
to the amplifier outputs. The special design allows con-  
nection of large diameter speaker cable while reducing  
shock hazard due to the high output power of MXa  
amplifiers.Thehotterminalofeachoutputpairisthered  
one; the black one is signal ground.  
If you are operating the amplifier in bridgedmode,  
connect the speaker load across the red terminals only;  
the red terminal of Channel 1 then is hotor in-phase.”  
The red terminal of Channel 2 is not grounded, however,  
so use the same precautions in handling and dressing  
the wire that you would for the normal hotoutputs.  
CONTROLS AND DISPLAYS  
The SIGLED indicates signal levels that are -30 dB  
The front panel-mounted attenuator controls are labeled  
indBofattenuationandarecontinuouslyadjustablefrom  
0 dB (full gain) to (full kill).  
(referenced to full output power) or higher.  
When the amplifier is shut off, the amplifier should mute  
both channels virtually instantaneously, with the PROT”  
indicators lit until the power supplies are discharged.  
The LED displays for each channel function as follows:  
ON/OFF MUTING  
The PROTindicator lights  
whenever the output is muted. At  
turn-on, the amplifier mutes for a  
few seconds; at turn-off, it mutes  
immediately and remains muted  
until the power supplies have  
drained.  
PWR SIG  
CLIP PROT  
LED  
COLOR  
PWR  
SIG  
Green  
Yellow  
Red  
Main power supply active on this channel.  
Shows signal is present  
NO SIGNAL  
PWR SIG  
CLIP  
Shows output capability is being  
exceeded, with clipping distortion  
Only the PWRLED is lit. This is  
normal.  
CLIP PROT  
PROT  
Red  
Shows when the output is muted by  
protection circuitry.  
Table 1: LED Display Operation  
NORMAL SIGNAL  
The PWRLED is lit, and the  
SIGLED is lit or flashing. This  
is normal.  
CLIP PROT  
PWR SIG  
AC POWER  
Any MXa Series amplifier can be wired for 100, 120, or  
220240 VAC, 50 or 60 Hz operation. Unless it is spe-  
cially ordered, each amplifier is configured for the line  
voltage in the market for which it is intended. For ex-  
ample, those intended for Japan are 100 VAC; for North  
and Central America, 120 VAC; for Europe and most of  
Asia, 220240 VAC.  
OCCASIONAL CLIPPING  
The PWRand SIGLEDs are lit,  
and the CLIPLED flashes on  
occasional peaks. This is normal.  
CLIP PROT  
PWR SIG  
STEADY CLIPPING  
ThePWR,SIG,andCLIPLEDs  
are lit continuously. The channel is  
in hard clipping, and you should  
reduce power immediately to avoid  
speaker damage.  
CLIP PROT  
PWR SIG  
The power cord has a plug for connecting to a standard  
AC source. For 120-volt operation, the plug is a standard  
15-amperegroundedNEMAfitting;itmeetssafetyagency  
requirements for current consumption of less than 12  
amperes during normaloperation, but peak current  
draw under heavy usage can be much higher.  
THERMAL MUTING  
PWR SIG  
The SIGLED is flashing, and the  
PROTLED is lit; this indicates  
that the protection circuitry is mut-  
ing the output. The condition will  
reset itself when conditions allow.  
CLIP PROT  
KEY  
Not Illuminated  
Flashing  
Full Brightness  
Figure 5: LED displays further explained.  
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PROBLEM: Hum in the audio  
Because of its grounded-collector output  
TROUBLESHOOTING  
transistor configuration, which maximizes  
thermal efficiency, the signal ground on an  
MXaamplifiercannotbelifted.Theamplifiers  
balancedinputsaremeanttorejecthum,but  
if hum remains a problem, check the tight-  
ness of the two mounting screws on the  
standard input panel; if they are loose, the  
panelitselfmightnotbewellgroundedtothe  
chassis.Ifyouhaveanyproblemswiththese  
screws, contact the QSC Customer Service  
Department. In some cases, such as when  
the audio signal cables are routed near  
lighting dimmers that use triacs, you may  
need to use input isolation transformers be-  
cause of the extremely high noise field pro-  
duced by the dimmer circuitry. See the para-  
graphs on Open Input Architecture for fur-  
ther information on input transformers.  
PROBLEM: Channel will not come out of muting  
If reducing the gain control to attenuation  
does not release muting, the channel is  
defective or overheated (seeOverheating,”  
below).  
If reducing the gain releases the muting,  
raise the gain back up slowly while you  
watch the SIGand CLIPindicators; the  
problem may be an abnormal signal (with  
excessive ultrasonic energy, for example)  
that could otherwise damage your speak-  
ers.  
PROBLEM: No sound  
Is the channel muted? (If the PROTindica-  
tor is lit, the channel is muted; see below.)  
In addition, be sure to check wiring to assure  
that shields are properly terminated and no  
ground loops have been created.  
Is the SIGLED lit or flashing? (If so, the  
speaker is open or blown, there is an open  
circuit in the speaker wiring, or there is an  
open circuit in the internal output wiring of  
the amplifier.)  
PROBLEM: Overheating  
If the SIGindicator is dark, there is prob-  
ably not enough signal, or even none at all.  
Try turning up the front panel attenuators or  
boosting the signal level at the input.  
The thermal management system on an  
MXa Series amplifier features either a two-  
speed fan (MX 1000a, MX 1500a, and MX  
2000a) or a variable-speed fan (MX 3000a)  
that modulates the cooling air flow over the  
heatsinks in response to the cooling needs.  
If the air flow is blocked, however, or if the  
amplifier is overdriven into very low imped-  
ance loads, the amplifier could overheat  
even though the fan is running at full speed.  
IftheSIGindicatorshowslittleornoactivity  
but the CLIPLED is lit or flashing, there is  
probablyashortcircuitinthespeakerwiring.  
It is also possible, but less likely, that the  
channels output relay is defective and will  
not open, thereby short-circuiting the chan-  
nel output and producing the same symp-  
toms.  
At approximately 55°C, the fan runs at high  
speed.  
At approximately 80˚ C, the thermal limiter  
on the MX 3000a will start to reduce gain, up  
to 15 dB as needed, to reduce the amount of  
heat produced.  
PROBLEM: Channel goes into muting, with PROT”  
LED on  
If the fan is running full speed, the channel  
probably suffers from severe overheating.  
Unless there is a blockage in the flow of  
cooling air, the channel should return to  
normalwithinaminuteorso(seeOverheat-  
ing,below).  
Atapproximately85˚C,thechannelsoutput  
relay will mute the output. The channel will  
remain muted until the temperature drops to  
asafelevel.Evenwhilethechannelismuted,  
the SIGand CLIPindicators will function  
normally. If the CLIPindicator is flashing or  
continuously lit, reduce the gain to hasten  
the cool-down and prevent repeated ther-  
mal shutdowns.  
If the fan is not running at full speed, or the  
channel does not reset to normal after a  
cool-down period, the muting is probably  
because of a DC fault or other amplifier  
failure, especially if the SIGor CLIPindi-  
cators are lit even with the attenuator turned  
all the way down.  
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SPECIFICATIONS  
FTC Watts Per Channel 20Hz-20kHz, 0.1% THD EIA Watts Per Channel 1kHz, 1% THD  
MODEL  
8Load  
4Load  
8Load  
4Load  
2Load*  
MX 1000a  
MX 1500a  
MX 2000a  
MX 3000a  
250  
350  
450  
800  
350  
500  
650  
1200  
275  
400  
475  
850  
400  
600  
725  
1300  
500  
750  
1000  
1600  
*typical  
Bridged Mono 20Hz-20kHz, 0.1% THD  
Bridged Mono 1kHz, 1% THD  
MODEL  
16Load  
8Load  
4Load*  
MX 1000a  
MX 1500a  
MX 2000a  
MX 3000a  
500  
700  
900  
1600  
700  
1000  
1500  
2000  
3200  
1000  
1300  
2400  
*typical  
MX 1000a  
MX 1500a  
MX 2000a  
MX 3000a  
DYNAMIC HEADROOM  
8 ohms  
2.0  
2.3  
2.0  
2.5  
2.0  
2.5  
1.9  
2.9  
4 ohms  
DISTORTION  
SMPTE-IM  
Less than 0.05%  
FREQUENCY RESPONSE  
20 Hz to 20 kHz, ±0.15 dB  
8 Hz to 100 kHz, +0, -3 dB  
DAMPING FACTOR  
NOISE (A-weighted)  
VOLTAGE GAIN, dB  
Greater than 200  
100 dB below rated output (20 Hz to 20 kHz)  
40 (32 dB)  
1.1  
50 (34 dB)  
1.07  
56 (35 dB)  
1.05  
80 (38 dB)  
1.0  
SENSITIVITY, V RMS  
(for rated power, 8-ohms)  
INPUT IMPEDANCE  
CONTROLS  
10K unbalanced  
20K balanced  
Front: AC Switch, Ch. 1 and Ch. 2 Attenuator Knobs  
Rear: Parallel/Stereo/Bridge Switch  
INDICATORS (per channel)  
PWR:  
SIG:  
CLIP:  
PROT:  
Green LED  
Yellow LED  
Red LED  
Red LED  
8
 
MX 1000a  
MX 1500a  
MX 2000a  
MX 3000a  
CONNECTORS (each channel)  
COOLING  
Input:  
Output:  
Barrier strip and 1/4RTS phone jack  
Touch-Proofbinding posts  
MX 1000a, MX 1500a, MX 2000a: 2-speed fan with back-to-front air flow  
MX 3000a: Continuously variable speed fan, with back-to-front air flow  
AMPLIFIER PROTECTION  
Output Averagingshort-circuit protection, open circuit, ultrasonic, RF, thermal  
muting (thermal limiting also on MX 3000a). Stable into reactive or mismatched  
loads.  
LOAD PROTECTION  
Turn-on/turn-off muting, clip limiting (MX 3000a only), DC-fault load grounding  
relay with internal fault fuses.  
OUTPUT CIRCUIT TYPE  
MX 1000a, MX 1500a, MX 2000a: Complementary linear stage with  
2-step high-efficiency circuit  
MX 3000a: Complementary linear stage 3-step high-efficiency circuit  
POWER REQUIREMENTS  
100, 120, 220-240 VAC, 50/60 Hz  
POWER CONSUMPTION  
Normal operation: 1/8 power @ 4per channel  
Maximum: full power @ 2per channel  
Divide current by 2 for 220-240 VAC operation  
Normal Operation @ 120 VAC  
Maximum @ 120 VAC  
4A  
22A  
5.5A  
29A  
7.5A  
38A  
<12A  
58A  
DIMENSIONS  
Faceplate Width  
Chassis Depth  
Standard 19" (48.3 cm) Rack Mounting  
17.9(45.5 cm) deep (to support rear ears)  
Faceplate Height (2 rack spaces)  
Faceplate Height (3 rack spaces)  
3.5(8.9 cm)  
3.5(8.9 cm)  
5.25(13.3 cm)  
5.25(13.3 cm)  
WEIGHT  
Shipping, Lbs  
Net, Lbs  
49 lbs/22.2 kg  
42 lbs/19 kg  
49 lbs/22.2 kg  
42 lbs/19 kg  
62 lbs/28 kg  
54 lbs/24.5 kg  
74 lbs/33.8 kg  
69 lbs/31 kg  
OPEN INPUT ARCHITECTURELEVEL I  
On the rear of an MXa or EX amplifier are an upper and  
a lower input panel; both are easily removable for future  
upgrades. ThisistheconceptofOpenInputArchitecture,  
and the opening in which the panels mount is called the  
slot. As installed at the factory, the lower is the MXa or  
EX standard input panel and the upper one is a blank. A  
ribbon cable connects the slotpanels to the rest of the  
amplifier. It carries input signals, speaker output monitor  
signals, muting status, and clip activity; these are for  
supporting future accessories and remote control sys-  
tems. Although the physical dimensions of the MXa and  
EX panels are the same, their internal cabling is different  
and the MXa platform does not support all the EX  
functions. The MXa Open Input Architecture slot thus is  
designated as Level Iand the EX as Level II.”  
The MX-1 Input Expander panel may be installed in the  
upper panel position. It features XLR inputs and addi-  
tional 1/4RTS inputs. Installation instructions are in-  
cluded with the expansion kit.  
Other accessories include a stereo precision attenuator  
(for the lower panel position) and a cinema crossover (for  
the upper panel position). More are in development.  
The standard input panel shipped with each MXa Series  
amplifier has balanced 1/4(6.3 mm) RTS phone jacks  
and barrier strip inputs and the Parallel-Stereo-Bridge  
switch. The panels circuit board has solder footprints for  
passive roll-off circuit components, input isolation trans-  
formers, and other special customizations.  
9
 
INSTRUCTIONS FOR BRIDGED  
OPERATION  
PARALLEL, STEREO, OR BRIDGED  
OPERATION  
1. Set the switch to the Bridgeposition.  
The Parallel-Stereo-Bridge switch is located on the input  
panel, next to the input jack for channel 1).  
2. Connect the signal to channel 1s input only.  
Do not connect anything to the input of  
channel 2.  
The most commonly used operating mode for a power  
amplifier is Stereo,in which the two channels are  
independent and separate all the way from input to  
output. Set the switch in the center position for stereo  
operation.  
3. Turn up the gain on channel 2 all the way.  
Use channel 1s gain control to set the level.  
Both channels’ “SIGand CLIPindicators  
should flash identically. (If you have used  
other amplifiers, this step may be different.  
But it is correct; in the bridged mode, chan-  
nel 2 receives its feed from a sample of  
channel 1s output. The sample is calibrated  
such that channel 2, at full gain, will produce  
a voltage equal in magnitude but opposite in  
polarity to channel 1s.  
Paralleltiesthetwochannelinputstogethersothatboth  
will be driven by the same signal, without the need for  
externaljumpersorwiring. Aftertheinputsbothchannels  
operate independently; though they carry the same sig-  
nal, their gain controls affect only their respective chan-  
nels, and they must use separate speakers. Never par-  
allel the speaker outputs!  
The Bridgeposition uses both channels to provide  
about three times the power to a single speaker load that  
a single channel does. In this position the switch feeds  
channel 2 with an inverted signal from channel 1. Thus,  
when one channel pushes,the other pulls,providing  
twice the voltage swing of a single channel.  
4. Connect the single speaker load across the  
red binding posts of the amplifier outputs as  
shown in Figure 2-2. The positive speaker  
wire goes to channel 1, and the negative to  
channel 2.  
BRIDGED-MONO MODE CAUTION:  
TIP NEG RING POS  
SLEEVE GND  
The voltage across the outputterminals ofa bridgedMXa  
amplifier may equal or exceed 100 volts rms and may be  
as high as 170 volts (MX 3000a), 130 volts (MX 2000a), or  
120 volts (MX 1500a). Use fully insulated CLASS ONE  
wiring, andthe loadmustbe ratedforupto2400watts (@  
8 ohms) for the MX 3000a, 1300 watts (@ 8 ohms) for the  
MX 2000a, 1000 watts (@ 8 ohms) for the MX 1500a, and  
700 watts (@ 8 ohms) for the MX 1000a.  
STEREO  
PARALLEL  
BRIDGE  
CH 1  
Figure 6: Parallel-Stereo-Bridge switch shown in the  
normal (Stereo) mode position.  
VORSICHT BEIM ÜBERBRÜCKTEN  
MONO-MODUS:  
STEREO  
Switch on Input Panel  
(Left side of rear panel)  
PARALLEL  
BRIDGE  
Zwischen den überbrückten Terminals eines MXa-  
Verstärkers besteht eine Ausgangsspannung mit einem  
quadratischen Mittelwert von mehr als 100 Volt und  
vielleicht von bis zu 170 Volt (MX 3000a), 130 Volt (MX  
2000a), oder 120 Volt (MX1500a). Zu verwenden ist voll  
isolierte Verdrahtung der US-Klasse Eins, und die  
angeschlossene Belastung muß für bis zu 2400 Watt (8  
Ohm) beim MX 3000a, 1300 Watt (8 Ohm) beim MX 2000a,  
1000 Watt (8 Ohm) beim MX 1500a, und 700 Watt (8 Ohm)  
beim MX 1000a ausgelegt sein.  
BRIDGED MONO  
+
+
CHANNEL 2  
CHANNEL 1  
CLASS 2 WIRING  
STEREO 4 OHM MIN/CH.  
BRIDGED MONO 8 OHM MIN. CLASS 1 WIRING MUST BE USED  
BRIDGED MONO OPERATION: PLACE BRIDGING SWITCH ON INPUT PANEL  
TO BRIDGED POSITION. CONNECT INPUT SIGNAL TO CH 1 ONLY.  
CONNECT SPKR (+) TO CH 1 (+) OUTPUT. CONNECT SPEAKER () TO  
CH 2 (+) OUTPUT. SET CH 2 GAIN FULLY CLOCKWISE AND REGULATE  
LEVEL WITH CH 1 GAIN CONTROL.  
+
CONNECT ONE SPEAKER LOAD ONLY.  
Figure 7: For Bridge mode, use CH 1 input only, and set  
Input switch and connect load as shown.  
10  
 
AC CURRENT CONSUMPTION  
VI. LONG-TERM OUTPUT  
POWER  
A major objective in the design of the MXa Series  
amplifierseven the highest-powered modelsis to  
permit their operation from readily available, standard  
ACpowersources.TheMX3000acandeliver1600watts  
per channel into 2-ohm loadsa total of 3200 wattsyet  
its rated current draw under normal conditionsis less  
than 12 amperes at 120 volts AC, which is 1440 watts.  
In a properly designed sound system, you can usually  
obtain the desired sound level without using the full  
outputpoweroftheamplifier;iftheCLIPindicatorsflash  
once in a while, that is perfectly normal.  
Iftheamplifierisoperatedatextremelyhighpowerlevels,  
it may overheat or may even damage the speakers. The  
amount of stress on the amplifier depends largely on the  
load and how hard the amplifier drives it. In general, the  
lower the load impedance, the more stressful the load is.  
How is this possible? First, normal conditionsin power  
amplifier rating means operation, using pink noise as a  
source, at an average power level equal to one-eighth of  
maximum power. This is recognized by most of the  
worlds safety agencies as the loudest you can play  
music through an amplifier and still keep the incidence of  
clipping to a reasonable minimum. An amplifiers peak  
current draw at full output power into 2 ohms is several  
times what the normaldraw is, but its various protection  
circuits will prevent this conditions lasting more than a  
minute or two.  
8-Ohm Loads  
The amplifier can operate at practically any power level  
without risk of overheating. However, if it is pushed hard  
enough to continually light the CLIPindicator, the  
amplifiers average output power can reach 250 to 800  
watts (depending on the model), which is more than  
many speakers can handle.  
When you plan the AC power hookups for your amplifi-  
ers, use Table 2 to predict the current requirements per  
amplifier. You can use the one-eighth power figures to  
predict the normal continuous current draw, then add a  
safety margin to allow for occasional crescendos.  
4-Ohm Loads  
If the CLIPindicator flashes occasionally, the amplifier  
is approaching its maximum long-term power capacity. If  
it is lit about half the time, the amplifier channel will  
probably go into thermal protection within a few minutes.  
2-Ohm Loads  
Except for an occasional flash, keep the CLIPindicator  
dark to avoid overheating the amplifier channel.  
Table 2: Current requirements, in amperes, at 120 VAC under various conditions (divide by 2 for 220240 VAC operation):  
Output  
AC Current  
AC Current  
AC Current  
AC Current  
MODEL Load power  
@ Full power @ 1/3 power @ 1/8 power @ Idle  
MX 1000a  
MX 1500a  
MX 2000a  
MX 3000a  
8+8  
4+4  
2+2  
275 x 2  
400 x 2  
500 x 2  
10  
15  
22  
5.5  
7.5  
10  
3
4
5
1
1
1
8+8  
4+4  
2+2  
400 x 2  
600 x 2  
750 x 2  
14  
21  
29  
7
11  
13  
4
5.5  
6.5  
1
1
1
8+8  
4+4  
2+2  
475 x 2  
725 x 2  
1000 x 2  
16  
25  
38  
9.5  
15  
21  
5
7.5  
11  
1
1
1
8+8  
4+4  
2+2  
850 x 2  
25  
40  
58  
16  
31  
42  
9.5  
15  
20  
1
1
1
1300 x 2  
1600 x 2  
11  
 
HEAT EMISSIONS  
Essentially, a power amplifier draws electrical energy  
from the AC mains, converts it to DC, and then converts  
itagainintoananalogoftheinputsignaltosendouttothe  
loudspeakers. Any AC power that enters the amplifier  
through the power cord and does not exit through the  
speaker outputs turns into heat, which the amplifier must  
rid itself of by exhausting it to the outside. In indoor use  
this may present a sizeable challenge to a buildings air  
conditioning system. Use Table 3 to predict the heat that  
will be emitted by your amplifier.  
Table 3: Heat emissions of MXa amplifiers under various conditions:  
Load 1/3 Power, both channels 1/8 Power, both channels Idle, both channels  
MODEL  
MX 1000a  
BTU/hr  
1035  
kcal/hr  
BTU/hr  
580  
kcal/hr  
150  
BTU/hr  
kcal/hr  
8Ω  
4Ω  
2Ω  
265  
365  
545  
75  
75  
75  
20  
20  
20  
1430  
2140  
270  
305  
915  
1035  
MX 1500a  
MX 2000a  
MX 3000a  
8Ω  
4Ω  
2Ω  
1165  
1875  
2770  
295  
475  
700  
770  
1010  
1415  
195  
255  
360  
110  
110  
110  
28  
28  
28  
8Ω  
4Ω  
2Ω  
1850  
3100  
4730  
470  
785  
1080  
1755  
2760  
275  
445  
700  
145  
145  
145  
40  
40  
40  
1195  
8Ω  
4Ω  
2Ω  
2980  
7100  
755  
1795  
2600  
2015  
3600  
5040  
510  
910  
200  
200  
200  
50  
50  
50  
10280  
1275  
PROTECTION CIRCUITS  
The design goal in high-efficiency, lighter-weight ampli-  
fierssuchastheMXaSeriesistocontrolmorepowerwith  
fewer or smaller load-bearing components, e.g., resis-  
tors, transistors, transformers, etc. However, the higher  
power flow through these components makes effective,  
responsive protection circuitry absolutely vital. To this  
end,thedesignoftheMXaseriestakesacomprehensive  
approach to protection.  
ing the speakers when the amplifier is turned on or off.  
The turn-on delay is approximately three seconds to  
allow the power supplies and circuitry to stabilize. Turn-  
off muting occurs almost immediately after power is shut  
off. Muting occurs whether power is turned on and off  
using the front panel power switch or externally at the AC  
source.  
An NTC (negative temperature coefficient) thermistor in  
series with the power switch and transformer primary  
limits inrush current. The thermistor initially has a high  
resistance, which then diminishes rapidly as it warms, to  
avoid power loss. Typically, the inrush current of an MXa  
Series amplifier thus is equal to that of another amplifier  
of about 1/3 to 1/2 its power rating.  
As in all QSC amplifiers, the inputs are resistively buff-  
ered for overload and RF protection. Chassis bypass  
capacitors at inputs and outputs further improve RF  
rejection.  
MXa amplifiers use the proven Output Averagingshort  
circuit protection system. This circuit permits full output  
current even into resistive or reactive 2-ohm loads, but  
reduces the current safely by about 75% if the output is  
shorted.  
When the DC fault protection circuitry senses a DC  
voltage on the amplifier output, it activates a relay which  
shorts the output and load to ground. If the DC is due to  
a fault in the amplifier channels output circuitry, it will  
probably produce enough current flow to blow the fault  
fuseinserieswiththeoutput.Thiswilldisablethechannel  
Turn-on/turn-off muting keeps transientsboth from the  
amplifieritselfandfromupstreamequipmentfromreach-  
12  
 
output until it can be repaired, at which time the fuse  
should be replaced also.  
VIII. TECHNICAL ASSISTANCE  
& SERVICE  
Temperature sensors on the channel heatsinks and the  
power transformers are part of the thermal management  
circuitry. On the MX 1000a, MX 1500a, and MX 2000a,  
the temperature sensors govern whether the dual-speed  
fan should run at low or high speed. Below 55˚ C, the fan  
runs at low speed; above, it runs at high speed. At or  
above 85˚ C, the channel mutes to go into thermal  
protection.  
Servicing your unit requires a trained technician capable  
of performing the type of service you need. There are no  
user serviceable components inside your unit and the  
danger of electric shock exists. Additionally, some of the  
components in your unit has QSC specific parts that  
require QSC replacements. Comprehensive service  
manuals for some models are available at QSC.  
On the MX 3000a, the thermal management circuitry  
controls the variable-speed fan according to how much  
cooling air flow is required. At and above 80˚ C, the  
thermal limiting circuit reduces the audio signal by up to  
15 dB. At 85˚ C, the channel mutes to go into thermal  
protection.  
TECHNICAL ASSISTANCE  
If you suspect that your [product] is defective, check your  
system configuration and [product] settings to determine  
the origin of the problem. In many cases, incorrect audio  
interfacing, poor cabling, or other system level impair-  
ments are the cause of problems in audio systems. For  
technical assistance beyond the information given in this  
manual, QSC Technical Services may be contacted.  
VII. WARRANTY AND  
DISCLAIMERS  
FACTORY SERVICE  
DISCLAIMER  
Intheeventthatyour[product]doesneedfactoryservice,  
you may reach QSC Technical Services for return in-  
structions. A Return Authorization (RA) number must be  
obtained from QSC Technical Services. QSC may not  
account for products that are returned without a Return  
Authorization number.  
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 SPL-1.  
PRODUCT WARRANTY  
QSC Audio Products, Inc. guarantees the SPL-1 to be  
free from defective material and/or workmanship for a  
period of three years from date of sale, and will replace  
defective parts and repair malfunctioning products under  
this warranty when the defect occurs under normal  
installation and useprovided the unit is returned to our  
factory via prepaid transportation with proof of purchase  
(sales receipt). This warranty provides that examination  
of the returned product must disclose, in our judgment, a  
manufacturing defect. This warranty does not extend to  
any product which has been subject to misuse, neglect,  
accident, improper installation, or where the date code  
has been removed or defaced.  
Product Return Guidelines  
1. Pack the product well for protection during ship-  
ment. QSC will provide the factory packaging free  
of charge upon request.  
2. Include a copy of the sales receipt, your name,  
return address, phone number, and defect de-  
scription with your return correspondence.  
3. Call QSC Technical Services for a Return Autho-  
rization number.  
4. Mark the Return Authorization number on the  
outside of the packaging.  
5. Ship the product prepaid to QSC Audio Products.  
We recommend United Parcel Service (UPS).  
QSC TECHNICAL SERVICES  
1675 MacArthur Blvd  
Costa Mesa, CA 92626  
Telephone: (800) 772-2834  
(714) 957-7150  
(714) 754-6175  
Fax: (714) 754-6173  
Bulletin Board: (714) 668-7567  
13  
 
File Library  
QSControl Hardware Support  
QUALIFIED SERVICE CENTERS  
QSC maintains a service center network for your conve-  
nience. If you choose to return your product to a local  
service center, you may call QSC Technical Services for  
a referral. Accessories, input modules and other periph-  
eral QSC products must be returned to the factory for  
service.  
QSControl Software Support  
EX, MXa, VS, USA, and Series One  
Slot Accessories  
General Notes  
File Types  
Graphics  
Mechanical drawings  
Specifications  
Application notes  
INTERNATIONAL SERVICING  
Field service notes  
Service bulletins  
For QSC products that are purchased outside of the  
United States, service must be referred to the distributor  
or dealer from where the product was purchased. There  
are numerous service centers in many countries. The  
service centers in your country may be located by your  
dealer, distributor, or by contacting QSC Technical Ser-  
vices.  
Schematics  
Pin-outs  
Owners manual text segments  
Environment files  
Computer utilities and drivers  
Service manual text segments  
Computer configuration tips  
Block diagrams  
These are primarily text, graphics, utility, and program files.  
IX. QSC ONLINE  
Security Levels  
New User  
Full User  
QSC User  
Sysop  
Cursory access, for review  
Customer access  
Full access  
If you have a computer with a modem you can take  
advantage of QSCs convenient technical support bulle-  
tin board system, QSC OnLine. Download software  
updates, messages, or hardware application notes; up-  
load questions, comments, and useful tips, and more.  
This service is available free of charge, around the clock,  
Supervisory access  
User Privileges and Security  
New User  
Full User  
QSC User  
30 minutes per day  
No uploads  
No downloads  
365 days a year (366 days in leap years).  
Standard messages access  
Bulletin access  
As of March 18, 1994  
90 minutes per day  
5 uploads per day  
BBS Hours:  
24 hours a day  
BBS Telephone Number:  
(714) 668-7567  
5 downloads per day  
Standard messages access  
Bulletin access  
General  
Automatic system maintenance hours:  
Unlimited time per day  
10 uploads per day  
1:00 a.m.2:00 a.m. Pacific Time  
(no log-ons during this hour)  
10 downloads per day  
Unlimited messages access  
All menu and system access  
System type:  
Host location:  
Open (no subscription fee)  
QSC Customer Service Department  
Costa Mesa, California  
*Uploads and messages subject to verification and editing by the sysop.  
Support Areas  
Communications Settings  
Bulletins  
14400 bps (also supports 1200, 2400, and 9600 bps)  
Advertisements  
8 bits, no parity, 1 stop bit  
Ordering and Support Information  
Newsletter  
Conferences  
Mail Messages  
General Forum  
Parts & Accessory Ordering  
Technical Commentary  
QSControl Hardware Support  
QSControl Software Support  
EX, MXa, VS, USA, and Series One  
Slot Accessories  
General Notes  
14  
 
X. IMPORTANT ADDRESS AND  
TELEPHONE INFORMATION  
Factory address:  
QSC Audio Products, Inc.  
1675 MacArthur Boulevard  
Costa Mesa, California 92626-1468  
USA  
Factory telephone numbers:  
Main Number  
(714) 754-6175  
Sales Direct Line  
Sales  
(714) 957-7100  
(800) 854-4079  
(toll-free in U.S.A. only)  
Sales & Marketing FAX  
(714) 754-6174  
(714) 957-7150  
Customer Service  
Customer Service  
(800) 772-2834  
(toll-free in U.S.A. only)  
Customer Service FAX  
QSC OnLine Technical  
(714) 754-6173  
(714) 668-7567  
15  
 
®
A
U
D
I
O
QSCis a registered trademark of QSC Audio Products, Inc.  
1675 MacArthur Blvd. Costa Mesa, CA 92626  
(714) 754-6175 FAX (714) 754-6174  
 

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