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Power Amplifier

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Power Amplifier
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The RMXa Series is an update on a proven line of amplifiers line of amplifiers combining legendary QSC reliability, audio performance and affordability. Entertainers and touring users can continue to rely on the RMXa as one of the leading amplifier series in the world. For mid-power applications, the 2RU models offer 4Ω power ratings from 300 to 800 watts per channel. For premium loudspeaker systems with extremely high power capacity the 3RU models (RMX 4050a and RMX 5050a) are unchallenged.

The RMXa Series amplifiers from QSC offer true professional-quality performance at an affordable price.

Rackspace And Comprehensive Features

Three 2-rackspace models range in power from 430 to 1200 watts per channel at 2 ohms. Two 3-rackspace models provide 2000 to 2500 watts per channel at 2 ohms. All five models feature a compact chassis less than 16” deep.

RMXa amplifiers include a comprehensive set of features including XLR and 1/4” balanced inputs, Speakon® and binding post outposts for convenient connectivity. User-defeatable clip limiters and selectable low-frequency filters optimize sonic performance.

Sustained Power, Extraordinary Performance And Reliability

QSC’s RMX 5050a power amplifier represents state-of-the-art in professional quality performance at an affordable price. Perfectly suited for a wide range of sound reinforcement applications including professional touring, performing musicians, and mobile entertainers, the RMX 5050a is optimized to deliver high levels of sustained power, extraordinary audio performance and road-proven reliability.

The RMX 4050a is a “heavy duty” model designed to work as hard into 2 ohm loads as most competing amplifiers will at 4 ohms.

Three-tier, Class H Design

Both the RMX 5050a and RMX 4050a feature a three-tier, Class H design that is extremely efficient at real world power levels. Less AC current is wasted and more available current goes into producing useful audio power. 120 volt versions of the RMX4050a accomplish all this with a standard 15 amp plug.


  • Compact size — up to 2500 watts in two rack spaces, or 5000 watts in three rack spaces
  • High-current toroidal transformers, for greater 2-ohm power and low noise
  • Independent user-defeatable clip limiters reduce distortion
  • Selectable low-frequency filters (30 Hz or 50 Hz) protect speakers and increase headroom
  • The 4000-watt RMX4050a operates on a standard 15 amp plug (120V)
  • Both the RMX4050a and the RMX5050a feature a dual mono, high-current power supply for increased reliability and performance
  • The RMX4050a's particularly exceptional combination of cooling capacity and electrical efficiency provides robust thermal performance suitable for high continuous power in 2-ohm stereo or 4-ohm bridged applications.
  • Balanced 1/4” (6.3 mm) TRS, XLR, and barrier strip inputs
  • Touch-proof binding post and Neutrik Speakon® outputs
  • Front mounted gain controls for easy access
  • Signal and clip LED indicators for monitoring performance
  • Independent DC and thermal overload protection on each channel automatically protects amplifier and speakers
  • 3-year warranty plus optional 3-year extended service contract

Technical Specifications


RMX 850a

RMX 1450a

RMX 2450a

RMX 4050a

RMX 5050a

Power per Channel, Stereo Mode (both channels driven)

8Ω, FTC 20 Hz–20 kHz, 0.1% tdD

185 W

260 W

450 W

800 (650**) W

1050 W

8Ω, EIA 1 kHz, 0.1% tdD

200 W

300 W

500 W

850 W

1100 W

4Ω, FTC 20 Hz–20 kHz, 0.1% tdD

280 W

400 W

650 W

1300 W

1600 W

4Ω, EIA 1 kHz, 0.1% tdD

300 W

500 W (0.5% tdD)

800 W

1400 W

1800 W

2Ω, FTC 20 Hz–20 kHz, 1% tdD

1600 W

2000 W

2Ω, EIA 1 kHz, 1% tdD

430 W

700 W

1200 W

2000 W

2500 W

Power, Bridge-Mono Mode

8Ω, FTC 20 Hz–20 kHz, 0.1% tdD

530 W

800 W

1300 W

2600 W

3200 W

8Ω, EIA 1 kHz, 0.1% tdD

600 W

900 W

1500 W

2800 W

3600 W

4Ω, EIA 1 kHz, 1% tdD

830 W

1400 W

2400 W

4000 W

5000 W

Signal to Noise (20 Hz–20 kHz)

-100 dB

Distortion (SMPTE-IM)

< 0.01%

< 0.02%

Input Sensitivity at 8Ω

1.15V (+3.4dBu)


(+4.0 dBu)

1.42V (+5.3 dBu)

Voltage Gain

31.6x (30 dB)

40x (32 dB)

50x (34 dB)

64x (36 dB)

Output Circuitry

Class AB

2-tier Class H

3-tier Class H

Current Draw (120 V AC)

Typical, 1/8 power pink noise at 4Ω*

Severe, 1/3 power pink noise at 4Ω*


4.5 A

6.6 A


6.0 A

9.6 A


6.3 A

15.6 A


10.0 A

20.1 A


13.9 A

26.9 A

AC Mains Plug



NEMA 5-15



NEMA 5-20






35 lb (15.9 kg)

41 lb (18.6 kg)


40 lb (18.2 kg)

46 lb (20.9 kg)


44.5 lb (20.2 kg)

50.5 lb (23 kg)


68 lb (30.8 kg)

77 lb (34.9 kg)


75 lb (33.1 kg)

87 lb (37.2 kg)

Distortion (typical)

20 Hz–20 kHz, 10 dB below rated power

1 kHz and below, full rated power


< 0.03% tdD, 4Ω and 8Ω

< 0.03% tdD, 4Ω and 8Ω


< 0.02% tdD, 4Ω and 8Ω

< 0.02% tdD, 4Ω and 8Ω

Frequency Response

20 Hz–20 kHz: +0/-1 dB -3 dB points: 5 Hz and 50 kHz (LF filter bybassed, 8Ω)

Damping Factor (1 kHz and below)

> 300 at 8Ω

> 250 at 8Ω

Input Impedance

10 kΩ unbalanced; 20 kΩ balanced

Input Stage Clipping

10 V rms (+22 dBu)

6.4 V rms (+18 dBu)


Continuously variable speed fan, back-to-front air flow

Connectors (each channel)

Input: Active balanced; 3-pin Euro-style detachable terminal block and XLR (pin 2+)

Output: Touch-proof binding posts; Neutrik Speakon®


Front: AC switch; Channel 1 & 2 gain knobs

Rear: 10-position DIP switch

LED Indicators

Power on: Green; Signal: Yellow (1 per channel); Clip/Protect: Red (1 per channel)

Amplifier Protection

Full short circuit, open circuit, tdermal, ultrasonic, RF protection. Stable into reactive or mismatched loads

Load Protection

Turn-on/off muting; AC coupling (850, 1450); Triac crowbar (1850HD, 2450, 4050HD, 5050) on each channel


3.5” (8.9 cm) tall; 2 rack spaces

5.25” (13.3 cm) tall; 3 rack spaces

Power Requirements

100, 120, 230 V AC (factory configured), 50–60 Hz

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