QSC RMX 850a Two-Channel Power Amplifier


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The RMXa Series amplifiers offer true professional-quality performance at an affordable price. With 300 watts per channel into 4 ohms and 430 into 2 ohms, all in a chassis that is less than 16" deep, the RMX850a is perfectly suited for performing musicians and mobile entertainers.

QSC RMX850a Two Channel Power Amplifier Features:

  • Compact 2 rack space size.
  • Up to 860 watts in bridge-mono & 430 watts in stereo mode.
  • Professional quality performance - incorporates road-proven QSC designs.
  • High-current toroidal transformers for greater two-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.
  • Balanced 1/4" (6.3mm) TRS, XLR and barrier strip inputs.
  • Binding post and Neutrik Speakon outputs.
  • Front mounted gain controls for easy access.
  • Signal and Clip LED indicators to monitor 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.

QSC RMX 850a Specifications
 RMX 850a
Power per Channel, Stereo Mode (both channels driven)
8Ω, FTC 20 Hz–20 kHz, 0.1% THD185 W
8Ω, EIA 1 kHz, 0.1% THD200 W
4Ω, FTC 20 Hz–20 kHz, 0.1% THD280 W
4Ω, EIA 1 kHz, 0.1% THD300 W
2Ω, FTC 20 Hz–20 kHz, 1% THD
2Ω, EIA 1 kHz, 1% THD430 W
Power, Bridge-Mono Mode
8Ω, FTC 20 Hz–20 kHz, 0.1% THD530 W
8Ω, EIA 1 kHz, 0.1% THD600 W
4Ω, EIA 1 kHz, 1% THD830 W
Signal to Noise (20 Hz–20 kHz)-100 dB
Distortion (SMPTE-IM)< 0.01%
Input Sensitivity at 8Ω1.15V (+3.4dBu)
Voltage Gain31.6x (30 dB)
Output CircuitryClass AB
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
AC Mains Plug

NEMA 5-15

35 lb (15.9 kg)
41 lb (18.6 kg) 
Distortion (typical)
 20 Hz–20 kHz, 10 dB below rated power
 1 kHz and below, full rated power

< 0.03% THD, 4Ω and 8Ω
< 0.03% THD, 4Ω and 8Ω
Frequency Response20 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
Input Impedance10 kΩ unbalanced; 20 kΩ balanced
Input Stage Clipping10 V rms (+22 dBu)
CoolingContinuously 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® 
ControlsFront: AC switch; Channel 1 & 2 gain knobs
Rear: 10-position DIP switch 
LED IndicatorsPower on: Green; Signal: Yellow (1 per channel); Clip/Protect: Red (1 per channel)
Amplifier ProtectionFull short circuit, open circuit, thermal, ultrasonic, RF protection. Stable into reactive or mismatched loads
Load ProtectionTurn-on/off muting; AC coupling (850, 1450); Triac crowbar (1850HD, 2450, 4050HD, 5050) on each channel
Dimensions3.5” (8.9 cm) tall; 2 rack spaces
Power Requirements100, 120, 230 V AC (factory configured), 50–60 Hz

The RMX 850a Box Includes:

(1) QSC RMX 850a Amplifier
(1) Quick Start Guide
(1) Adhesive Rubber Feet Kit (For non rack-mount applications)
(1) Rear Rack Ear Mounting Kit
(1) IEC Detachable Power Cord

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