RMX 1850HD


QSC RMX 1850HD rear  
This gear is assigned to one of our Full Professional P.A. Rental systems. For more information on our Systems Rental, call us @ 210 521-8921.

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User Manual


The QSC RMX 1850HD is a professional, moderately priced stereo power amplifier housed in a sturdy 2 RU rackmountable chassis, offering 360 Watts of output power at 8 Ohms, and over 1800 Watts at 4 Ohms bridged. This model is uniquely equipped with an improved thermal protection design that allows for higher continuous power, and therefore better output performance, at 2-Ohm stereo and 4-Ohm bridged applications.

The RMX 1850HD also offers independent and defeatable clip limiters, and efficient power reserves created by a high current toroidal transformer, resulting in improved and consistent high level transient response. The XLR , 1/4″ TRS, and barrier strip connectors cover the standard input requirements, and the selectable 30 Hz and 50 Hz low frequency filters offer additional speaker protection and increased headroom. The outputs are on either barrier strips or the ever popular Speakon connectors.

The RMX 1850HD is packed with design features that contribute toward an excellent value for the budget-conscious but picky professional, and QSC is comfortable recommending the RMX series for studio monitoring or live sound system applications.



  • Rackmountable power amplifier with unique, advanced thermal protection; higher continuous power output at 2 Ohms Stereo and 4 Ohms Bridge-Mono applications
  • High-current toroidal transformer and filter capacitance for ensured energy reserves, improved high level transient response across variety of speaker loads
  • Output device direct-mounted to heat sink for optimum thermal coupling, cooling
  • 1800 Watts maximum power output
  • Independent defeatable clip limiters reduce distortion without affecting peak performance, response
  • Selectable low-frequency filters boost system response, protect speakers; match amplifier’s range to speakers for tighter LF response
  • Low-noise variable speed fans with rear-to-front air flow, keep amplifiers and racks cooler
  • Independent DC and thermal overload protection on each channel automatically protects amplifier and speakers


Power Rating Rating @ 1 kHz, THD=0.1%
600W @ 4Ω Stereo (per channel)
360W @ 8Ω Stereo (per channel)
900W @ 2Ω Stereo (per channel)
1200W @ 8Ω Bridged-Mono
1800W @ 4Ω Bridged-Mono

Rating @ 20 Hz – 20 kHz, THD=0.05%
550W @ 4Ω Stereo (per channel)
350W @ 8Ω Stereo (per channel)
1100W @ 8Ω Bridged-Mono

Damping Factor >300 (@8 Ohms)
Input Sensitivity 1.16 Vrms @8 Ohms
Input Impedance 20 kOhms, balanced
10 kOhms, unbalanced
Gain 33dB
Frequency Response 20 Hz – 20 kHz, +/- 1dB
Signal-to-Noise Ratio 100dB (20 Hz – 20 kHz)
Total Harmonic Distortion (THD) <0.02%
Input Connections 2 x XLR female, balanced
2 x 1/4″ TRS phone, balanced
2 x barrier strips
Output Connectors 2 x pair 5-way binding posts
2 x NL-4 Speakon
Controls Front Panel 2 x rotary Level Control knobs
1 x Power switch
Controls (Rear) 1 x Bridge/Stereo/Parallel Input Config. Switch
1 x Clip/Limiter switch
2 x Top 100 Hz HPF/Full/Sub 100 Hz LPF Filter switches
2 x 33 Hz HPF/Full (infrasonic) Filter switches
Indicators 1 x green Power On LED
2 x yellow Signal LEDs
2 x red Clip LEDs
Cooling 1 x variable-speed fan (back-to-front airflow)
Power Consumption 6 Amps (1/8 power pink noise @4 Ohms)
Power Requirements 100-120VAC, 60Hz
Dimensions 19 x 3.5 x 15.9″ (483 x 89 x 404mm); 2U
Weight 44.5 lbs (20.2 kg)
Specialties Detented Level Attenuators
Comprehensive Protection Circuitry
On/Off Muting, DC-fault Power Supply Shutdown