The Boulder Amplifiers 851 Mono Power Amplifier represents the next evolution in high-fidelity amplification, bringing the revered performance and engineering pedigree of the acclaimed 861 Stereo Power Amplifier into a dedicated monoblock format. Designed for audiophiles and professional installations that demand pure, uncompressed power, the 851 Mono delivers 100 watts of continuous output into 8 ohms with phenomenal control, transparency, and musical authority.
At its core, the 851 Mono Power amp improves upon the proven amplifier design of the original 861 Stereo Power Amp, including ultra-wide bandwidth response, extremely low distortion, and robust protection systems. By simplifying the signal path, dedicating each chassis to a single channel, and implementing the ground-breaking Smart Current Technology Output Stage; Boulder’s engineers have extracted every bit of resolution and dynamic nuance from the design while enhancing headroom and channel separation.
The first amplifier in the 800 Series to implement the all new Smart Current Output stage.
Along with assembly and testing, every circuit board and piece of metalwork is produced in-house at Boulder's dedicated facility for unparalleled quality assurance
Boulder's traditional in-house 0.25" (6 mm) thumbscrew binding posts for secure speaker cable connections and optimal sound quality
Space saving design is the same footprint (width and depth) as the 812 DAC Preamplifier, and 808 Phono Preamplifier
The only Class-A amplifier in the 800 Series.
100 W Continuous Power into 8-Ohms
Sophisticated protection circuitry to prevent any potential damage to your system
Software updates to the internal control and housekeeping systems available as needed with automated online downloads or manual USB port installation
150 W Peak Power into 8 Ohms
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Specifications
- Continuous Power, 8 Ohms
- 100W
- Peak Power, 8 Ohms
- 150W
- Continuous Power, 4 Ohms
- 200W
- Peak Power, 4 Ohms
- 250W
- Peak Power, 2 Ohms
- 350W
- Balanced Analog Inputs
- 1 pair balanced via 3-pin XLR
- Outputs
- .25" (6mm) Binding posts
- Distortion, THD
- .002%
- Equivalent Input Noise (EIN), 20 kHZ
- 2.6 μV
- Input impedance
- 100kΩ Balanced
- Frequency Response, 20 Hz to 20kHz
- +0.00, -0.04 dB
- Frequency Response, -3dB
- 0.015 Hz, 150 kHz
- Maximum Analog Gain
- 26 dB
- Power Requirements
- 100V, 120V, 240V 50 - 60 Hz
- Power Consumption
- 550W Maximum
- Dimensions
- 12" x 12" x 3.5"
- Weight
- 22 lbs
Manufacturer's Description — Boulder Amplifiers
The Boulder Amplifiers 851 Mono Power Amplifier represents the next evolution in high-fidelity amplification, bringing the revered performance and engineering pedigree of the acclaimed 861 Stereo Power Amplifier into a dedicated monoblock format. Designed for audiophiles and professional installations that demand pure, uncompressed power, the 851 Mono delivers 100 watts of continuous output into 8 ohms with phenomenal control, transparency, and musical authority.
At its core, the 851 Mono Power amp improves upon the proven amplifier design of the original 861 Stereo Power Amp, including ultra-wide bandwidth response, extremely low distortion, and robust protection systems. By simplifying the signal path, dedicating each chassis to a single channel, and implementing the ground-breaking Smart Current Technology Output Stage; Boulder’s engineers have extracted every bit of resolution and dynamic nuance from the design while enhancing headroom and channel separation.
The first amplifier in the 800 Series to implement the all new Smart Current Output stage.
Along with assembly and testing, every circuit board and piece of metalwork is produced in-house at Boulder's dedicated facility for unparalleled quality assurance
Boulder's traditional in-house 0.25" (6 mm) thumbscrew binding posts for secure speaker cable connections and optimal sound quality
Space saving design is the same footprint (width and depth) as the 812 DAC Preamplifier, and 808 Phono Preamplifier
The only Class-A amplifier in the 800 Series.
100 W Continuous Power into 8-Ohms
Sophisticated protection circuitry to prevent any potential damage to your system
Software updates to the internal control and housekeeping systems available as needed with automated online downloads or manual USB port installation
150 W Peak Power into 8 Ohms
Verified Dealers
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Authorized dealers for Boulder Amplifiers 851
- 3mA Audio — online and in-store — Houston, Texas, United States (website)
- Absolute Hi End — in-store — Ormond, Victoria, Australia (website)
- American Sound — in-store — Richmond Hill, Ontario, Canada (website)
- Ana Mighty Sound — online and in-store — Paris, Île-de-France, France (website)
- Audio Advisors — in-store — West Palm Beach, Florida, United States (website)
- Audio Element — in-store — Pasadena, California, United States (website)
- Audio Gallery — online and in-store — Las Rozas de Madrid, Comunidad de Madrid, Spain (website)
- Audio Y Cine — online and in-store — Sevilla, Andalucía, Spain (website)
- Class A Audio — in-store — Notting Hill, Victoria, Australia (website)
- David Lewis Audio — in-store — Philadelphia, Pennsylvania, United States (website)
and 35 more verified dealers
