Power amplifiers mono — Boulder 851

The 851 is a compact monoblock power amplifier from Boulder, built into a remarkably manageable chassis relative to the brand's broader flagship catalogue. The 851 brings Boulder's uncompromising American engineering to a space-efficient monoblock power amplification format.

Key specs that matter

Input impedance is a substantial 100,000 ohms balanced. Output power is 150W into 8 ohms, rising to 250W into 4 ohms. Gain is 28dBu. Total harmonic distortion plus noise is 0.002% at 100% global feedback. Maximum power consumption is 550W. At 304.8 x 304.8 x 88.9mm and 10kg, the 851 maintains a space-efficient monoblock chassis relative to Boulder's broader more substantial flagship monoblock catalogue.

Sound and use context

Expect exceptionally clean amplification reflecting the low 0.002% distortion figure, packed into this remarkably compact chassis reflecting Boulder's uncompromising engineering standards at a more accessible scale.

Pairing

As a monoblock, two units are needed for a stereo pair, and Boulder's own preamplifier catalogue offers natural, brand-coherent pairings.

Alternatives

Boulder's own 1163 offers a stereo power amplifier alternative within the same broader catalogue for buyers preferring a single-chassis solution.