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.


  • 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