We are an authorized QSC dealer, so full warranty applies from the date of purchase. If you have any further questions regarding this amp or QSC products please don't hesitate to contact us: brian@bigtimefans.com or 414-339-0557

This amp has a 120V/60Hz USA spec power supply, so it will not operate on 230V/50Hz power

FEATURES

• Power levels matched to the most popular speakers used by entertainers
• 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 26 lbs (12.5 kg)
• 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

The GX3 is a class B amplifier, how does this differ from the more common class AB?

The GX3 is a Class B design, as distinct from Class AB. True Class B requires that the positive output stage turn off exactly when the negative stage turns on, and vice versa. If the positive and negative stages overlap, you have Class AB operation, which ensures against any discontinuities, but results in an idle current which creates losses and needs careful bias tracking circuitry. If you have a gap between positive and negative actuation, you actually have "Class C" operation, which is indeed unsuitable for audio due to crossover distortion. Many actual attempts at Class B design end up with Class C results, due to poor understanding of on-off delays, feedback stabilization, and lack of loop gain.

In effect, Class B is the exact dividing line between Class C (no idle current, but distorted), and Class AB (idle current assures continuity, at the expense of extra heat). To optimize efficiency and power in a compact chassis, and eliminate problems of bias tracking, the GX series is set up for zero idle current. Careful design techniques and high closed-loop feedback ensure that there is no appreciable crossover gap, qualifying us to claim "true Class B" as an indicator that we combine maximum efficiency with no perceptible distortion. To put this in practical terms, the GX Class B design achieves less crossover distortion than many imitators of our Class AB designs.

Bottom line - the GX is "Class B done right".

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.

The GX5 is specified as a Class H amplifier, what does this mean?

In a Class H system, the output devices are normally powered from a low power rail but shift to a high power rail in less than a millionth of a second when the program material demands higher output. This generates less loss and allows the design to output more power in a smaller and lighter chassis. The GX5 is a 2-tier Class H design where the output devices operate as Class B within each tier.

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™

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.

What is GuardRail? Is it just a fancy name for a clip limiter?

GuardRail is a combination of two protective systems, clip limiting and thermal limiting. QSC recognizes that many of our users want to squeeze the last drop of dynamic range from their amplifiers, and the reality is that this means the amps will sometimes be pushed to clipping. Just as a drag race wouldn't be the same without the roaring engines and screeching tires, high energy music isn't the same without some evidence that the gear is giving its maximum peak performance. Therefore, QSC's Guardrail is not intended to prevent all clipping, just as you wouldn't want a race car to stop short of full power. However, we don't want our users "spinning out" or damaging their gear, so some kind of backstop is desirable - a guardrail, if you please. The GX measures the onset of clipping, using the activity of the Clip LED, which is driven whenever the global feedback loop detects that the output is no longer able to track the input. This method automatically takes into account all variables of load impedance, AC voltage, and power supply dynamics. Mild triggering of the Clip LED does not trigger clip limiting. Prolonged, heavy clipping causes a "slow" limiter to gradually reduce volume until the percent of clipping is reasonable. This method does not change the beat-to-beat dynamics, and allows for momentary clipping, but intervenes as gently as possible if gross overload is detected.

Similarly, if the amplifier overheats, the gain will be gradually reduced to prevent the need for thermal muting. The combination of these two features keeps the show "on the road" without limiting the dynamics of the performance any more than absolutely necessary. Users are encouraged to monitor the Clip LED to determine if they are overdriving the amp, but we recognize that during a show, your attention is most likely to be focused on giving the best possible performance, and the amplifier should basically take care of itself.

Subwoofer/Satellite Crossover

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.

How does the crossover in the GX Series work?The 100 Hz, 3rd order low pass/2nd order high pass crossover in the GX Series amplifiers is designed for a satellite/subwoofer combination where the sub takes over the low frequency portion of the music allowing the full-range speaker to play louder.

With the rear panel crossover switch enabled, a full-range signal on the channel 1 input will send 20 Hz - 100 Hz to the subwoofer connected to the channel 1 output and 100 Hz - 20 kHz to the full-range satellite speaker connected to the channel 2 ouput. 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.

For stereo operation you would of course need two GX amplifiers, but this configuration has some distinct advantages over using one amp for tops and one for subs. Input connections are simplified as you only need to send one cable to each amp from your board. And by driving only one sub per amplifier, when a heavy low frequency section hits, the amplifier's power supply can use the excess headroom from the relatively lighter loaded full range channel.

GX Series
SPECIFICATIONS	GX3	GX5
8 ohms / 1 kHz (both channels driven)	300 W	500 W
8 ohms / 1 kHz (single channels driven)	350 W	600 W
4 ohms / 1 kHz (both channels driven)	425 W	700 W
4 ohms / 1 kHz (single channels driven)	500 W	850 W
Distortion (typical)   20 Hz - 20 kHz, 1 dB below rated power	8 ohms: less than 0.05% 4 ohms: less than 0.1%
Signal to Noise (20 Hz - 20 kHz)	100 dB
Input Sensitivity	1.2 Vrms
Voltage Gain (8 ohms)	32.2 dB	34.4 dB
Output Circuitry	Class B	2-tier Class H
Power Requirements (1/8 power, pink noise at 4 ohms, 120V)	6.3A	6A
Frequency Response	20 Hz - 20 kHz, +0, -1 dB
Dynamic Headroom (4 ohms)	2 dB
Input Impedance (ohms)	Greater 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 -35 dB Blue Power LED, AC on
Rear Panel Controls	Full Range / Crossover switch 100 Hz, 3rd order LP (sub), 2nd order HP (top)
Dimensions	Height: 3.5" (89 mm) 2RU Width: 19" (483 mm) Depth: 10.1" (257 mm)
Weight	Net: 25 lbs (11.5 kg) Shipping: 30 lbs (13.5 kg)	Net: 26 lbs (12 kg) Shipping: 31 lbs (14 kg)
Agency Approvals	UL, CE, RoHS/WEEE Compliant
AC Power Consumption	AC Current and Heating, 120 VAC   GX3 GX5 Operating Condition AC amps BTU / hr AC amps BTU / hr Idle 0.2 44 0.3 60 8 + 8 ohms, 1/8 power 1 4.1 904 3.3 734 8 + 8 ohms, 1/3 power 2 6.1 1160 8.5 1456 8 + 8 ohms, full power 3 9.75 1109 16.2 1891 4 + 4 ohms, 1/8 power 1 6.3 1515 5.8 1160 4 + 4 ohms, 1/3 power 2 9.4 2105 11.2 2162 4 + 4 ohms, full power 3 15.0 2297 24.5 3754 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

* At onset of clipping

All Specifications Subject to Change Without Notice.

Inputs XLR, 1/4" TRS and phono input connectors for compatibility with any source.

Crossover Subwoofer/Satellite crossover built-in.

Outputs to Speakers Speakon® combo output connector accepts 1/4" or Speakon 2 wire connectors. Binding post output for compatibility with any loudspeaker wiring scheme .