QSC GX3 Power Amplifier

2-channel Power Amplifier, 425W Program/ch at 4 ohms, with Load Protection, Crossover Switch
QSC GX3 Power Amplifier image 1
QSC GX3 Power Amplifier image 1
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QSC GX3 Power Amplifier
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A Lightweight Power Amp That Really Packs a Punch!

The QSC GX3 425-watt power amplifier gives your speakers the power they need while giving you the efficiency and protective features you want for easy operation and peace of mind. The GX3 uses advanced components for both light weight and reliability. Its Guardrail protection allows delivery of peak power while preventing overloads. It's equipped with a crossover switch, so adding a subwoofer to your system is a snap. Optimized for 4- and 8-ohm speakers, this amp also fits perfectly into popular racks, and its lightweight design (less than 30 lbs.) makes the GX3 incredibly easy to transport.

QSC GX3 425-watt Power Amplifier at a Glance:
  • The right amount of power for your application
  • Efficient operation
  • GuardRail: protection from overloads
  • Subwoofer-ready when you are

The right amount of power for your application
GX amplifiers deliver just the right amount of power to the most popular speakers used by entertainers. Most loudspeaker manufacturers recommend an amplifier with power output equal to the speaker's "Program (Music) Power" rating or two times the "Continuous (RMS) Power" rating.

The GX3 is ideal for speakers in the 300 watt (Program) range, while the GX5 provides full performance for 500 watt (Program) speakers. Both models supply maximum possible power to 4 ohm and 8 ohm loads. Owners of popular 4 ohm loudspeakers (dual-woofer, two-way models and many subwoofers) will find the 700 watt (4 ohm) power of the GX5 an ideal match.

Efficient operation
The GX3 uses the latest evolution of the QSC Grounded Collector output system, for optimum cooling of the critical power transistors. A true Class B biasing system combines maximum thermal efficiency with excellent audio performance. The GX5 uses a Class H system, based on key elements of the PLX Series, almost doubling power in the same size and weight. QSC design expertise allows the output devices to shift from low-power to high-power rails in less than a millionth of a second, ensuring that the output power is always right where it needs to be without excess loss.

Both amplifiers use premium toroidal power transformers for reliable "mid-weight" performance. A variable-speed fan moves air crosswise through the amplifier, drawing cool air in over the power transformer, through the fan, and then over the heat sink. This keeps the transformer cool and allows a full size heat sink to fit in a down-sized chassis. As always, the amplifiers are fully protected from the usual hazards of the trade, ensuring stable performance and long life.

GuardRail: protection from overloads
GuardRail protection delivers full peak power while preventing detrimental overloads. During excessive clipping, or extreme overheating, GuardRail reduces gain just enough to preserve the integrity of the music, protect the speakers and keep the audience excited, without unprofessional distortion levels or shutdowns.

Subwoofer-ready when you are
A subwoofer reduces strain on the full-range speaker, allowing it to play louder, or letting a smaller speaker do the same job. The GX Series supports this mode with a Crossover switch that splits the full-range input entering Ch 1, sending 20 Hz - 100 Hz to the sub (Ch 1) and 100 Hz - 20 kHz to the top box (Ch 2). The front panel gain controls balance the sub and top box, while GuardRail optimizes peak power into the sub and top individually, for greater musical impact and dynamic range.

QSC GX3 425-watt Power Amplifier Features:
  • Power levels matched to the most popular speakers
  • Optimized for maximum real-world headroom into 4 ohm and 8 ohm speaker systems
  • Inputs: XLR, 1/4" TRS and phono input connectors for compatibility with any source
  • 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.
  • Minimum depth chassis (10.1" / 257 mm) fits in compact, inexpensive effects racks
  • Lightweight - less than 30 lbs.
  • 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 at 4 ohms/1kHz (both channels driven): 425W
  • Distortion (typical): 20Hz-20kHz, 1dB below rated power

  • Dynamic headroom (4 ohms): 2dB
  • Input impedance (ohms): reater than 20k (balanced)
  • Maximum input level: +24 dB (16 Vrms)
  • Input connectors (each channel):
    3-pin XLR and 1/4" TRS, balanced, parallel
    Phono, unbalanced

  • Output connectors (each channel)
    Speakon, 1/4", binding posts

  • Amplifier and load protection:
    Short circuit; open circuit; thermal; RF protection; load protected against DC faults

  • Front-panel controls and indicators: Gain controls, 21 detents; red clip LEDs, proportional, 0.1% THD threshold; green signal LEDs, threshold -35dB; blue power LED, AC on
  • Rear panel controls: Full range/crossover switch
    100Hz, 3rd order LP (sub), 2nd order HP (top)

  • Dimensions" Height: 3.5"/2RU;
    width: 19"; depth: 10.1"
  • Net weight: 27 lbs.
The QSC GX3 gives you the right wattage for your system!

Additional Media

Power Amp Buying Guide

Tech Specs

Number of Channels 2
Power Class Class H
Watts/Side @ 8 ohms 300W
Watts/Side @ 4 ohms 425W
Inputs 2 x XLR, 2 x 1/4", 2 x RCA
Outputs 2 x SpeakON, 2 x Binding Posts
Cooling System Variable-speed fan with rear-to-front airflow
Rack Spaces 2U
Height 3.5"
Depth 10.1"
Width 19"
Weight 27 lbs.
Manufacturer Part Number GX3

Customer Reviews

Based on 14 reviews
Write your review


Quiet , clear sound , built like a Mack Truck
Music background: hobbyist

lil amp, big punch!

This amp very sturdy. When I got it out of the box I was expecting something a lil more fragile and soft on the exterior. But its solidly built. I didn't see any difference in material construction than the qsc rmx 2450 I have also. The sound is also very clear, prestine and tight. I use this amp to power up a pair of old tweeter cqabinets and it does a very good job
Music background: Musician/DJ

Solid Amp

Power amps aren't too sexy. You just want one to sound really great and take the abuse it's gonna get regularly. This one does all that - for less than $300!. I use it for floor monitors. It sounds great. Power is clean. Lows are tight, punchy and defined. Highs are airy and sweet, not harsh at all. Excellent amp. I was going to go with a Crown amp at the same price. Sweetwater was temporarily out of stock and Tim Harrington pointed me to this one. Great call. It's a great amp! Thanks Tim.
Music background: Live Sound Engineer, Music Director


Not much else needs to be said about this amp that hasn't already been said. I would definitely say from my experience with pro audio and specifically with amplifiers, this GX3 gives you the power it says it gives. There are plenty of amplifiers out there that say they have lot's of power, but really only put a little. This amplifier backs up what it promises.
Music background: Worship Leader, Sound Engineer

One Great Amp

I purchased two of thes units for our Church. I originally was going to run one for the main speakers and the other for the monitor speakers. I decided initially to just try and use one amp to drive both the mains and the monitors by daisy chaining. I was skeptical that the one amp would be over driven and not be able to power both. Boy was I wrong ! The one amp provided way more power than I needed for the mid size sanctuary. The sound was powerful and crystal clear. The QSC amps seem to be very well made and come with a reputation second to none. It's all backed up with a 6 year warranty. I don't think there is any amp out there that offers as much bang for the buck !
Music background: Live Sound Engineer
See also: Power Amps, QSC, QSC Power Amplifiers