Mono Power Amplifier

Upon its release, the 850 Mono Amplifier was the beginning of a new chapter in Boulder’s storied history: the first amplifier in the 800 Series, from the company whose products have captured and monitored some of the most important music and film scores of all time.

Please contact your authorized Boulder dealer for availability


  • Powerful 200W output from a surprisingly compact chassis

  • Unique half-width casework allows for installation in both audio and home cinema systems

  • Rugged, easy-to-connect, high-current speaker terminals require no tools

  • Advanced microprocessor-controlled protection circuits for trouble-free operation

  • Proper use of feedback to maximize bandwidth and minimize distortion without affecting sound quality

  • Programmable Boulder Link to turn on multiple 850s and transmit their status to any Boulder preamplifier's display

  • Large toroidal transformer is encased in a steel housing, potted, and damped to eliminate vibration or hum

  • Multiple filter capacitors assure a fast, low-impedance power supply

  • Supervising microprocessor oversees all functions and communicates with other Boulders during turn-on and turn-off


Mono Power Amplifier
  • Continuous Output Power, 8 / 4 ohms


  • Peak Output Power, 4 ohms


  • Magnitude Response, 20 Hz to 20 kHz

    +0.00, -0.04 dB

  • Magnitude Response, -3 dB at

    0.015 Hz, 150 kHz

  • THD at Continuous Power

    20 Hz to 2 kHz: 0.0016%
    2 kHz: 0.009%

  • Signal-to-Noise Ratio (re: 200W/8Ω)

    -109 dB, unweighted,
    20 to 22 kHz

  • Common Mode Rejection (Balanced Only)

    60 Hz: 90 dB,
    10 kHz: 70 dB

  • Voltage Gain

    26 dB

  • Input Impedance

    Balanced: 50k ohms,
    Unbalanced: 25k ohms

  • Input Connections

    Balanced via 3-pin XLR

  • Control Systems Supported

    Boulder Link, 12V trigger

  • Weight

    Amplifier: 30 lbs. (13.6 kg)
    Shipping: 35 lbs. (15.9 kg)

  • Power Requirements

    100, 120, 220-240 VAC, 50-60 Hz
    3W Standby, 800W Maximum