PLX Series Professional Audio Amplifiers
User Manual
®
4-ohm minimum impedance models with Speakon output terminals:
PLX 1104
PLX 1804
2-ohm minimum impedance models with Speakon and binding post terminals:
PLX 1802
PLX 2502
PLX 3102
PLX 3602
*TD-000214-00*
TD-000214-00 Rev.B
Introduction
Thank you for purchasing this QSC power amplifier. Please read the following directions to obtain the best results. This manual covers all
models of the PLX series. Illustrations show the PLX 1804 to be representative of the PLX 1104 and 1804 models, while the PLX 3602 illus-
tration is representative of the PLX 1802, PLX 2502, PLX 3102, and PLX 3602 models.
The PLX 1104 and PLX 1804 models feature:
•4-ohm minimum impedance
•Speakon loudspeaker connections
•QSC PowerLight high-performance, compact, and light weight switching power supply
•Complete amplifier protection
•XLR and 1/4-inch TRS balanced input connectors
•Gain controls are recessed and 21-step detented
•Active inrush current limiting eliminates need for power sequencing
•LED indicators for power, input signal presence, -10 dB, and clip/protect
•Rear chassis tabs and front panel design protect controls and connectors
In addition, the PLX 1802, PLX 2502, PLX 3102, and PLX 3602 models feature:
•2-ohm minimum impedance
•Bridgeable output
•Binding post loudspeaker connections
•Clip limiter
•33 Hz low frequency filter
•Low-cut/full-range/high-cut selector
•Stereo/bridge mode/parallel input selector
•Front panel LED indicators for parallel and bridge modes
Unpacking
Factory packed carton contains:
•PLX amplifier
•User's manual
•Adhesive rubber feet (for non-rack mount applications)
•IEC-type detachable power cord
Use the same type carton when shipping the amplifier.
Front Panel
1- Power Switch
2- Cooling Air Exhaust Vents
3- LED Indicators
4- Gain Controls
3
Rear Panel
1- Input Configuration switch
2- 1/4-inch TRS input connectors
3- XLR female input connectors
4- Low Frequency Filter switches
5- Speakon output connectors
6- Binding post output connectors
7- Cooling air inlet vents
8- Clip Limiter switch
9- Serial number plate
10- IEC-type AC mains inlet
11- Circuit breaker, resettable
Rack Mounting
The front panel casting includes features for
finger-lifting and gripping at each end.
Use four screws and washers to mount the amplifier to the
equipment rack rails. To use the amplifier outside a rack,
attach the self-adhesive rubber feet to the bottom.
For portable, mobile, or other applications where the rack
assembly may be moved, we strongly recommend support-
ing the rear of the amplifier. A rear rack ear kit is available
from QSC’s Technical Services Group.
The cast front panel includes finger grips at each end, mak-
ing lifting and setting into the rack more comfortable.
4
Cooling
Air flow in QSC amplifiers: Cool air is drawn into the
rear of the amplifier by the cooling fan. Warm air exits
the front of the amplifier.
Air flows from the rack, into the back of the amplifier, and out the
front. This keeps the rack cool. The fan automatically runs faster
when the amp is working hard.
Do not block the front or rear air vents!
AC Mains Connection
Connect AC power to the IEC socket on the back of the amplifier.
NOTE: Turn off the AC power switch before connecting AC power.
Connect the AC mains plug to a suitable AC mains outlet.
Orient the IEC connector with the connector prongs in
the socket, then push the connector firmly into the IEC
socket until fully seated.
The correct AC line voltage is shown on the serial number
label, on the rear panel. Connecting to the wrong line
voltage may damage the amplifier or increase the risk of
electric shock.
The rear chassis ear can be used to retain the IEC power
connector. After inserting the IEC block into the recepta-
cle, use a wire-tie or similar device to secure the cord to
the chassis ear.
AC Mains Current Draw
The table at the right provides typical current draw for each model as
a function of load and output power level. Units of measurement are
amperes rms.
NOTE! Current draw shown is for 120 VAC line. For 230
VAC models, multiply values shown by 0.5.
•1/8 power (pink noise) represents typical program with occa-
sional clipping. Use this rating for most applications.
•1/3 power (pink noise) represents severe program with heavy
clipping.
•Full power (sine) is continuous sine wave driven at 1% clipping.
•PLX 1802, PLX 2502, PLX 3102, and PLX 3602 models: Thermal
or overcurrent cutback limits duration of full power 2 ohm
operation. Long term, active limiting to 30A at 120V.
•PLX 1104 and PLX 1804 models: Long-term, circuit breaker lim-
ited to 15A at 120V.
5
Input Configuration Switch (PLX 1802/2502/3102/3602 models only)
Input Configuration selector switch
Select the input configuration by sliding the switch to the position which corresponds with the
desired input configuration.
•Bridge- upper position
•Stereo- middle position
•Parallel- lower position
Stereo Mode: Each channel remains independent, and each may be used for a different signal.
Parallel Mode: This setting connects both inputs together. One input signal feeds both chan-
nels. Do not connect different sources to each input. Each channel's Gain control and speaker
connection remain independent.
Clip Limiter ON/OFF switch
Bridge Mode: This setting combines both channels into a single channel with twice the output
voltage. Use only Channel 1’s input and Gain control. Set Channel 2's Gain control at minimum.
Use only one input when operating in parallel or bridge mode.
Low Frequency filter selection
switches for each channel
Clip Limiters (PLX 1802/2502/3102/3602 models only)
The amplifier has a clip limiter with an on-off switch. The limiter only responds to actual clipping,
and automatically compensates for load and voltage variations. Clip limiting is generally recom-
mended, especially to protect high frequency drivers.
•Set the switch UP (ON position) to use Clip Limiting.
•Set the switch DOWN (OFF position) to disable the clip limiter.
Low Frequency Filters (PLX 1802/2502/3102/3602 models only)
Each channel has independent filter selection of Full Range (infrasonic filter only), 33 Hz low cut,
100 Hz low cut, or 100 Hz High Cut. This allows tailoring the amplifier performance to that of the
loudspeakers, offering the best possible performance from the system. Proper filtering reduces
distortion and prevents amplifier overload.
TOP / FULL / SUB Switch: Select the type of loudspeaker being driven by each channel.
•Set the switch to the left for driving “top” boxes; applies 100 Hz low cut
•Set the switch to the middle position for “full range” loudspeakers.
•Set the switch to the rightmost position for driving subwoofers.
Low Frequency filter selection table
33 Hz (low cut) / FULL Switch: Unless the loudspeaker has extended low frequency capabil-
ity, we recommend setting the filter to the 33 Hz setting. The filter should only be set to FULL
(turned off) for driving subwoofers. Check the loudspeaker’s specifications and use the 33 Hz filter
if the loudspeaker’s low frequency capability does not extend below 33 Hz.
•Set to FULL when driving loudspeakers that have low frequency capability below 33 Hz or
in studio monitoring applications.
•Set to 33 Hz for loudspeakers which are not rated for frequencies below 33 Hz.
6
Inputs
Each channel has a balanced XLR (female) and 1/4-inch TRS input. The XLR and TRS
connectors for each channel are wired in parallel and can be used for “daisy chain-
ing” an input signal to additional amplifiers.
Input connectors and pinout
chart (PLX1802 shown)
The input impedance is 20k ohm balanced or 10k ohm unbalanced. Both XLR and TRS
inputs are connected with standard cables and can be changed quickly. Pinouts are
marked on the rear panel. Do not attempt to connect more than one input signal to a
given channel.
Balanced connections are recommended to reduce AC hum and interference, espe-
cially with long cable runs. Unbalanced connections may be suitable for short cables.
The signal's source impedance should be less than 600 ohms.
Input Pinouts
Balanced inputs: Connect to the plug as shown.
XLR
TRS
PLX 1104 and PLX 1804 models can parallel the input
signal to both channels by using a jumper from one
channel to the next:
•Connect the input signal to either of Channel 1’s
input connectors.
Unbalanced inputs: Connect to the plug as shown. If using an XLR connector, Pin 3
and pin 1 must be connected with a jumper as shown. If using a TRS connector, the
ring and sleeve must be connected with a jumper. If a TS connector is used, the
sleeve will provide the “jumper” when inserted into the input jack.
•Connect a jumper from Channel 1’s unused con-
nector to either of Channel 2’s input connectors.
Input signal
XLR
TRS
TS
TRS to TRS jumper from
Channel 1 to Channel 2
7
PLX 1104 and PLX 1804 Output Connectors: Do
not use less than 4 ohm impedance loads
with PLX 1104 and PLX 1804 models.
Outputs
The PLX 1104 and PLX 1804 models are equipped with Speakon output
connectors for each channel. PLX 1802, PLX 2502, PLX 3102, and PLX 3602
models are equipped with Speakon and binding post output connectors.
Wiring connections are shown on the back of the chassis. Carefully note
the markings and maintain consistent loudspeaker polarity for optimum
system performance.
Speakon Output Connectors
If making Speakon cables, be sure to connect the loudspeaker wiring as
shown on the chassis. Channel 1’s Speakon provides 4-wire (Ch 1 + Ch 2)
connection; Channel 2’s Speakon provides 2-wire (Ch 2 only) connection.
Appendix A provides Speakon connection reference.
Stereo and Parallel Mode: Connect each loudspeaker to its own chan-
nel of the amplifier, as shown on the chassis label. The INPUT CONFIGU-
RATION switch must be set for STEREO or PARALLEL mode.
Bridge Mode (PLX1802/2502/3102/3602 models only): Use Channel 1’s
Speakon for Bridge mode output connection. Bridge mode configures the
channel pair to drive a single high-power loudspeaker load. The INPUT
CONFIGURATION switch must be set for BRIDGE mode. Use only Channel
1’s input and Gain control. Set Channel 2’s Gain control at minimum.
PLX 1802, PLX 2502, PLX 3102, and PLX 3602
Output Connectors: Do not use less than 2 ohm
impedance loads with these models.
Binding Post Connectors (PLX 1802/2502/3102/3602
models only)
Stereo and Parallel Mode: Connect each loudspeaker to its own
channel of the amplifier, as shown on the chassis label. The INPUT
CONFIGURATION switch must be set for STEREO or PARALLEL
mode.
Bridge Mode: Bridge mode configures the channel pair to drive a
single high-power loudspeaker load. The INPUT CONFIGURATION
switch must be set for BRIDGE mode. Use only Channel 1’s input
and Gain control. Set Channel 2’s Gain control at minimum.
OUTPUT TERMINAL SAFETY WARNING! Do not touch
output terminals while amplifier power is on. Make all
connections with amplifier turned off. Risk of hazard-
ous energy!
8
LED Indicators
The LED indicators can be used to monitor system operation and identify common problems.
LED indicators on PLX 1104 and PLX
1804 models
POWER (PWR): BLUE
Normal indication:
•AC switch ON: LED will illuminate.
If no indication:
•Check AC power cord and AC outlet.
•Confirm that AC switch is in ON position.
CLIP: RED
Normal indication:
•Illuminates whenever the amplifier is driven beyond full power. The resulting distortion corre-
sponds to the brightness of the LED. Distortion that causes only brief flashing may not be audi-
ble.
•During muting, the red LED fully illuminates. This occurs during normal "On-Off" muting.
Abnormal indication:
•Bright red illumination while the amp is being used indicates either thermal muting or a shorted
output.
•If the amplifier overheats, the fan will run at full speed, and operation should resume within
one minute. Allow the fan to run, and make sure the amplifier ventilation is adequate.
•A shorted or overloaded output circuit will cause excessive Clip flashing and possible overheat-
ing.
•If distortion is audible without a Clip indication, the problem is either before or after the ampli-
fier. Check for damaged speakers or overloaded signal source. The amplifier Gain control
should be in the upper half of its range to prevent input overload.
SIGNAL (SIG), -10: GREEN
Normal indication:
•The SIG (signal) indicator illuminates when the input signal exceeds -35 dB, and the -10 (-10 dB)
indicator illuminates when the signal exceeds -10 dB.
LED indicators on PLX 1802, PLX 2502,
PLX 3102, and PLX 3602 models
If no indication:
•Check Gain settings and increase gain if necessary. Check input connections and audio source
for signal. If the Clip LED illuminates with little or no Signal indication, check the output wiring
for shorts.
Abnormal indication:
•If the SIG or -10 LED illuminates with no signal input, there may be system oscillations or some
other malfunction. Disconnect the load and fully reduce the gain. If the LED remains on, the
amp may need servicing.
BRIDGE MONO (BR M) and PARALLEL (PAR) (PLX 1802/2502/3102/3602 models only):
•Each channel pair has a AMBER LED for Bridge Mode, and a AMBER LED for Parallel mode.
These show how the rear panel INPUT CONFIGURATION switch is set (see Input Configuration
Switch). In Stereo mode, both LEDs should be OFF. In bridge mode the BR M indicator will be
illuminated. In parallel mode, the PAR indicator will be illuminated.
9
Gain Controls
Gain controls and LED cluster on PLX 1104 and
PLX 1804 models
Turn the GAIN controls clockwise to increase gain and
counter clockwise to decrease gain.
The GAIN controls are marked in dB of attenuation.
There are 21 detents for repeatable adjustments. The
upper 14 steps are about 1 dB each, and settings should
normally be made within this range. The range below -
14 dB should not be used for normal program levels, as
the input headroom could be exceeded, but can be used
for testing at reduced levels. At the minimum setting,
the signal is completely cut off.
Note! The GAIN controls do not adjust the
power of the amplifier. They adjust its sensi-
tivity to input signals.
Gain controls and LED cluster on PLX 1802,
PLX 2502, PLX 3102, and PLX 3603 models
Power Switch
Push in on the top of the rocker switch to apply AC mains
power to the amplifier. Push in on the bottom of the rocker
switch to turn the amplifier off.
When turned on, the blue PWR indicator LED and the red
CLIP indicator LED will illuminate; after a few seconds the
red CLIP indicator will extinguish.
10
Protection Systems
Both amplifier platforms are fully protected against adverse conditions, but their behavior and user adjustments are different.
PLX 1802/2502/3102/3602 models:
•Clip Limiting may be switched on the rear panel to prevent severe overdrive. This protects speakers and somewhat reduces
the load on the amplifier.
•Internal current limits protect the output transistors against overloading. Peak limiting may occur at full output if using more
than four 8-ohm speakers per channel, or if the speaker wiring is shorted. The red Clip LED will flash brightly, and the ampli-
fier may sound distorted. If the amplifier is driven hard under these conditions, the current limit will be further reduced,
causing an increase in distortion. If the amplifier appears to be losing power during peaks, check the speaker wiring and
number of speakers. Using Clip Limiting will reduce this distortion, but for best results do not exceed the rated loading.
•If the amplifier stops completely for several seconds after a very loud signal, it may be overloading the AC service. This only
occurs if the AC voltage sags more than 30%, and will be more likely if driving many speakers at once. Use short, heavy-
gauge AC cables and do not plug too many amplifiers into a single outlet.
•In Bridge Mono, the amplifier may shut down for several seconds if driven too hard into loads less than the rated 4-ohm
minimum.
•If the amplifier overheats due to prolonged overload or high external temperature, it will mute for about 30 seconds with the
fan running at full speed for maximum cooling. Make sure the rear intake is getting a free flow of cool air.
PLX 1104/1804 models:
•These models have completely automatic internal protection that maintains operation even under extreme conditions.
•Overdrive distortion will cause the red Clip LED to flash. If driven constantly into clipping, internal circuitry smoothly reduces
the volume to minimize distortion and stress.
•These models are rated for 4-ohm loads. Do not use more than two 8-ohm speakers per channel. Using too many speakers
may trigger limiting and cause a loss of volume.
•Internal current limits protect the output transistors against overloading. Moderate overloading will trigger clip limiting, and
smoothly reduce output level to prevent distortion. Severe overloading, such as driving the amplifier hard into a shorted
speaker wire, may cause short, rapid muting. Check the speaker wiring for shorts if the amplifier "chatters".
•Overheating may occur due to prolonged overdrive or high external temperature. This will first trigger thermal limiting,
reducing volume so that the amplifier remains below its thermal limit and keeps running. If input signals are still too high,
the amplifier may eventually mute for about 30 seconds with the fan at full speed for maximum cooling. Make sure the rear
intake is getting a free flow of cool air.
11
Specifications PLX 1104, PLX 1804
PLX 1104
PLX 1804
(1)
OUTPUT POWER (Watts)
20 - 20k Hz, 0.05% THD, 8 ohms/Ch.
1k Hz, 0.1% THD (EIA), 8 ohms/Ch.
20 - 20k Hz, 0.05% THD, 4 ohms/Ch.
1k Hz, 0.1% THD (EIA), 4 ohms/Ch.
310
325
500
550
550
600
800
900
DISTORTION, SMPTE-IM
FREQUENCY RESPONSE
SIGNAL to NOISE, unweighted, 20 - 20k Hz
VOLTAGE GAIN
0.02%
0.02%
20 - 20k Hz, 0.5 dB, all models
-108 dB
32.5 dB
-106 dB
34.9 dB
INPUT SENSITIVITY, Vrms
for rated power into 8 ohms
1.18 (+3.7 dBu)
1.20 (+3.8 dBu)
AB/H
OUTPUT CIRCUIT TYPE
INPUT IMPEDANCE
DYNAMIC HEADROOM
DAMPING FACTOR (8 ohms)
AMPLIFIER PROTECTION
COOLING
AB
10k ohms unbalanced, 20k ohms balanced
2 dB at 4 ohms
>200
Short circuit, open circuit, thermal, ultrasonic and RF protection. Stable into reactive or mismatched loads
Continuously variable speed fan; back-to-front air flow through heat sink array
CONTROLS
Front:
Back:
AC POWER switch, Gain controls (each channel) 21 detents
AC circuit breaker
LED INDICATORS
CONNECTORS
POWER (blue), SIGNAL (green x 2), -10 dB (green x 2), CLIP (red x 2)
Input:
1/4-inch TRS and female XLR; 20k ohm balanced, 10k ohm unbalanced
Output: Speakon connectors: Ch 1, 4-wires (Ch 1 + Ch 2); Ch 2, 2-wires (Ch 2 only)
LOAD PROTECTION
POWER REQUIREMENTS
DIMENSIONS
Turn-on/turn-off muting, DC fault blocking, Clip limiting, Infrasonic filter (-3 dB at 5 Hz)
Refer to rear panel serial number label. Configured at factory for 100, 120 or 220-240 VAC, 50- 60 Hz.
19.0" (48.3 cm) W, 3.5" (8.9 cm) H, 10.1" (25.7 cm) D (from front mounting rails, including rear support
ears)
WEIGHT(1)
13 pounds (5.9 kg) net; 18 pounds (8.2 kg) shipping
(1) NOTE: Due to special construction to meet EN-6100, CE models may have 5-12% (0.5 dBw) less power and 1.2 lb (0.6 kg) more weight.
U.S. patent no. 5767744 and patents pending
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
12
Specifications PLX 1802, PLX 2502, PLX 3102, PLX 3602
PLX 1802
PLX 2502
PLX 3102
PLX 3602
(1)
OUTPUT POWER (Watts)
20 - 20k Hz, 0.05% THD, 8 ohms/Ch.
1k Hz, 0.1% THD (EIA), 8 ohms/Ch.
20 - 20k Hz, 0.05% THD, 4 ohms/Ch.
1k Hz, 0.1% THD (EIA), 4 ohms/Ch.
1k Hz, 0.1% THD (EIA), 2 ohms/Ch.
Bridge Mono, 20 - 20k Hz, 0.1% THD, 8 ohms
Bridge Mono, 1k Hz, 0.1% THD, 8 ohms
Bridge Mono, 1k Hz, 1.0% THD, 4 ohms
320
330
525
575
425
450
675
750
1250
1400
1500
2500
550
600
900
1000
1550
1900
2100
3100
725
775
1100
1250
1800
2500
2600
3600
900
1100
1200
1800
DISTORTION, SMPTE-IM
FREQUENCY RESPONSE
SIGNAL to NOISE, unweighted, 20 - 20k Hz
VOLTAGE GAIN
<0.02%, all models
20 - 20k Hz, 0.5 dB, all models
-107 dB
31.9 dB
-106 dB
34.0 dB
-107 dB
35.0 dB
-107 dB
35.9 dB
INPUT SENSITIVITY, Vrms
for rated power into 8 ohms
1.28 (+4.4 dBu)
AB
1.15 (+3.4 dBu)
AB/H
1.23 (+4.0 dBu)
AB/H
1.25 (+4.2 dBu)
AB/H
OUTPUT CIRCUIT TYPE
INPUT IMPEDANCE
DYNAMIC HEADROOM
DAMPING FACTOR (8 ohms)
AMPLIFIER PROTECTION
COOLING
10k ohms unbalanced, 20k ohms balanced
2 dB at 4 ohms
>500
Short circuit, open circuit, thermal, ultrasonic and RF protection. Stable into reactive or mismatched loads
Continuously variable speed fan; back-to-front air flow through heat sink array
CONTROLS
Front:
Back:
AC POWER switch, Gain controls (each channel) 21 detents
Input Configuration Switch (Stereo, Parallel, Bridge), Clip Limiters (On/Off)
Subwoofer Switch (100 Hz Low Cut/Full Range/100 Hz High Cut, each channel)
LF Switch (33 Hz Low Cut/Full Range, 1 each channel)
LED INDICATORS
CONNECTORS
POWER (blue), SIGNAL (green x 2), -10 dB (green x 2), CLIP (red x 2), BRDG (amber), PAR (amber)
1/4-inch TRS and female XLR; 20k ohm balanced, 10k ohm unbalanced
Output: Speakon connectors: Ch 1, 4-wires (Ch 1 + Ch 2); Ch 2, 2-wires (Ch 2 only)
Binding posts
Input:
LOAD PROTECTION
POWER REQUIREMENTS
DIMENSIONS
Turn-on/turnoff muting, DC fault blocking, Clip limiting, infrasonic filter (-3 dB at 5 Hz).
Refer to rear panel serial number label. Configured at factory for 100, 120 or 220-240 VAC, 50- 60 Hz.
19.0" (48.3 cm) W, 3.5" (8.9 cm) H, 13.9" (35.3 cm) D (from front mounting rails, including rear support
ears)
WEIGHT(1)
21 pounds (9.5 kg) net; 26 pounds (11.8 kg) shipping
(1) NOTE: Due to special construction to meet EN-6100, CE models may have 5-12% (0.5 dBw) less power and 1.2 lb (0.6 kg) more weight.
U.S. patent no. 5767744 and patents pending
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE
13
Appendix A: Speakon Wiring Reference
Amplifier connection
To loudspeaker
Two-wire, single-channel connection
Four-wire, two-channel connection
NOTE! Ensure proper polarity when
connecting bridge mode output!
Bridge mode connection
14
How to Contact QSC Audio Products
Cómo comunicarse con QSC Audio Products
Comment prendre contact avec QSC Audio Products
Kontaktinformationen für QSC Audio Products
联系 QSC Audio Products
Mailing address:
Telephone Numbers:
Facsimile Numbers:
World Wide Web:
E-mail:
QSC Audio Products, Inc.
1675 MacArthur Boulevard
Costa Mesa, CA 92626-1468 USA
Main Number
(714) 754-6175
Sales & Marketing
Customer Service
(714) 957-7100 or toll free (USA only) (800) 854-4079
(714) 957-7150 or toll free (USA only) (800) 772-2834
Sales & Marketing FAX
Customer Service FAX
(714) 754-6174
(714) 754-6173
QSC Audio Products, Inc. 1675 MacArthur Boulevard Costa Mesa, California 92626 USA
©2006 “QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office.
|