Boulder Amplifiers 1151
The Boulder 1151 combines vibrant transparency with a warm, glowing musicality, delivering controlled bass, revealing tonal color, and an inviting freedom from sterility. Stereophile found it exceptionally open and alive, while measured results confirm wide bandwidth, low noise, and formidable 4-ohm power. This is a refined monoblock for listeners who want precision with genuine emotional pull.
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Deliciously Crispy
Sound Quality
92/100
Build Quality
91/100
Value for Money
85/100
Pros
Warm, vivid, and highly transparent presentation with controlled bass and strong differentiation of instrumental timbres.
Superb measured performance, including wide bandwidth, low noise, very low intermodulation distortion, and stable response into simulated speaker loads.
Delivers substantial output, exceeding its 8-ohm rating in measurement and reaching 500W into 4 ohms.
Cons
At maximum output into 2-ohm loads, protection engaged at 356W, limiting headroom for speakers with sustained ultra-low impedance demands.
Compared with the reviewer's reference amplifiers, it offered less low-end weight and somewhat less separation, three-dimensionality, and dynamic expression.
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What Reviewers Are Saying
SOUND QUALITY PERFORMANCE 92/100
The 1151 is described as unusually open, clear and vividly alive, while retaining a warm, inviting character rather than sounding dry or analytical. Its controlled bass and strong differentiation of instrumental timbres complement measured low distortion, wide bandwidth and very low noise.
Transparency Resolution
94/100
Stereophile found the 1151 "open, clear as a bell, vital, and alive," and specifically contrasted its vibrant transparency with another highly regarded amplifier. It also exposed differences in recorded horn timbres and color saturation, while measurements showed very low intermodulation distortion, low noise and clean square-wave behavior.
Tonal Balance Musicality
95/100
The listening report repeatedly emphasizes a "warm, glowing bath of sound" that drew the reviewer into the music. Bass was called solid and perfectly controlled, and the overall presentation was praised as warm, fresh and inviting without dryness or sterility.
Dynamics
91/100
The 1151 combines tightly controlled bass with substantial measured output, exceeding its 8-ohm specification by clipping at 310W. It also reached 500W into 4 ohms, though protection engaged at 356W into 2 ohms during measurement, so the greatest demands of ultra-low-impedance speakers may reduce available headroom.
Soundstage Imaging
90/100
The reviewer called the presentation marvelously illuminated and anything but monochromatic, with transparency that made the music especially vivid. There is less direct discussion of image placement, stage width or depth, but the reported openness and tonal color suggest a convincingly dimensional presentation.
Assessments of Build Quality, Usability, and Overall Propositions.
Build Quality
91/100
This is a fully balanced monoblock with solid-billet aluminum heatsinks and constrained-layer-damped feet. Its Smart Current bias approach is intended to provide Class-A character without traditional Class-A heat penalties, and measured operating temperatures remained notably restrained after extended testing.
Value for Money
85/100
At roughly $28,500 to $47,000 depending on market and configuration, the 1151 occupies a rarefied monoblock segment. The review praises its musical and technical performance strongly, but does not directly compare its asking price with competing amplifiers or make a clear value claim.
Reviews & Sources
Professional reviews and sources for this product's Watt'n Potatoes analysis.
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YouTube Reviews
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Specifications
- Continuous Power
- 250W
- Peak Power, 8 Ohms
- 350W
- Peak Power, 4 Ohms
- 600W
- Peak Power, 2 Ohms
- 750W
- THD, 8 Ohms, 250W
- 0.002%, 20kHz 0.01%
- THD, 4 Ohms, 250W
- 0.002%, 20kHz 0.01%
- THD, 2 Ohms, 250W
- 0.003%, 20kHz 0.02%
- Signal to Noise
- -108dB, 10-80KHz.
- Equivalent Input Noise (EIN), 20 kHz, BW
- 2.2 μV
- Magnitude Response, 20 Hz TO 20 kHz
- +0.00, -0.04 dB
- Magnitude Response, -3 dB at
- 0.015 Hz, 150 kHz
- Voltage Gain
- 26 dB
- Input Impedance
- Balanced: 200k ohms,\nUnbalanced: 100k ohms
- Common Mode Rejection (Balanced Only)
- 60 Hz: 90 dB, 10 kHz: 65 dB
- Input Connectors
- 3-pin balanced XLR
- Output Connectors
- Two sets of 6 mm / .250-inch wingscrews
- Weight
- Amplifier: 54 lbs. (24.5 kg),\nShipping: 64 lbs. (29.0 kg)
- Power Requirements
- 100, 110-120, 220-240 VAC, 50-60 Hz
- Power Consumption
- 10W standby, 60W idle, 800W at maximum output
Manufacturer's Description — Boulder Amplifiers
Boulder has the rare combination of technical and creative skills required to design this visually stunning and high-performance power amplifier.
Loudspeakers demand high-powered amplifiers to play at realistic levels. Even at low volumes, absolute control of the speaker is what makes you stop and listen.
Boulder has been providing this experience for over 40 years. Our history includes amplifiers that were used when capturing some of the greatest recordings ever made, so we know a thing or two about flawless audio reproduction. We also know that giving the 1151 Mono Amplifiers enough power to rein in the most challenging loudspeakers in a manageable package is the best way to bring these recordings to life in your home.
The heritage of Boulder’s 40 years of experience in amplifier design is evident in every aspect of the Boulder 1151 Mono Power Amplifier. Don’t take our word for it, we encourage you to hear it for yourself.
350W peak power per channel into 8 ohms, 600W peak power into 4 ohms, 750W peak power into 2 ohms
Space saving design is the same footprint (width and depth) as the 1110 Preamplifier and 1161 Stereo Amplifier and allows the use of a standard power cord
Class-A Smart Current biasing circuit
Newly developed protection circuitry safely and immediately shuts down the output section in case of shorted speaker cables or faults in the system and allows for greater peak power output
Smaller carton packaging means easier transportation, unpacking, and installation
Truly balanced input connections and output stage as with other 1100 Series products
Output stage uses 40 output transistors and 12 supply capacitors per chassis to ensure stable, high-power output into any load while maintaining detail and clarity.
The 1151 provides high amounts of current, making even the most difficult speaker perform to its fullest potential.
Dual speaker connections via easy to connect, high-current speaker terminals to accommodate bi-wired loudspeakers
Verified Dealers
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Authorized dealers for Boulder Amplifiers 1151
- 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
