Solid State Power Amp Reviews

I've been enthusiastically tracking the development of Bel Canto's class-D amplifiers, from their original TriPath-based">http://www.stereophile.com/amplificationreviews/442">TriPath-based models to their more">http://www.stereophile.com/musicintheround/1106mitr">more recent designs based on Bang & Olufsen's ICEpower modules. With each step, Bel Canto has improved their amps' sound quality and reliability.

I first saw Benchmark's AHB2 stereo power amplifier at the 2013 Convention of the Audio Engineering Society, in New York City. On silent display in Benchmark's booth on the convention floor, its compact size and comprehensive features made the amp immediately attractive, and the design was described as a departure from traditional analog and digital amplifiers. It was also explained to me that the AHB2 was based on designs by Benchmark's founder, Allen H. Burdick (whose initials it bears). By the time of Burdick's retirement, in 2006, Benchmark didn't yet offer a power amplifier, but the company used a prototype based on his work to evaluate their new digital products, and that amp was soon developed as a commercial product; Burdick died just weeks before the AHB2, now named in his honor, was shown at the 2013 AES convention.

I've been attending the annual Consumer Electronics Show for years, and usually come away with the impression that there are too many "me-too" products. I see a numbing similarity of approach of manufacturers within a chosen discipline: solid-state power amps in black and silver bristling with heatsinks, single-ended triode amps with their glow reflecting from bronze or wood panels, MCPU/DSP-centered devices with sleek, flat cases and intimidating remote controls, etc.

For several decades—from well before I toured the Boulder factory in 2016—I've wanted to get a handle on the best sound the now–41-year-old company can offer. Multiple listening sessions at shows had more than hinted at excellence. But neither my time in Boulder's large, dedicated music room, which was intentionally dry, nor exposure at various hi-fi shows left me convinced that I'd heard Boulder's full potential.

My first opportunity for an in-home audition came in 2021, when I reviewed the 866 stereo integrated amplifier ($17,500 with DAC, $16,000 without). But that entry-level (by Boulder standards) product, which Senior Engineer Jameson Ludlam said was released to build brand awareness and expand the company's reach by offering "a more accessible product that provides the features we think many people are looking for with the performance they have come to expect from Boulder," only provided a peek at the excellence I expected Boulder to achieve.

So when a last-minute review cancellation opened space to review the just-released Boulder 1151 mono power amplifier ($47,000/pair), I thought, "At last!"

How much power do you really need? How much power can you actually use? What's necessary, and what's icing on the cake? And does anyone really need 1000Wpc?

To high-end audiophiles, the Boulder 500 amplifier and its less expensive derivative, the 500AE (Audiophile Edition), would not seem to be "high-end" designs. They are designed around op-amps (felt by many to be generally poor-sounding), they have scads of negative feedback (which is perhaps why op-amps sound bad), and they have only a moderately hefty power supply. Why, then, is Stereophile publishing a review of an op-amp–based power amplifier? Read on...

Boulder Amplifiers, named after the Colorado town where the company has resided since its founding 23 years ago, makes some of the most elegant-looking solid-state amps around. Chassis are anodized, aircraft-grade aluminum with rounded edges, machined and finished in-house. The two models reviewed here, the 810 line preamplifier and the 860 power amplifier, each have a sleek, compact build—stacked atop each other, the two stand just over a foot high—owing to extremely efficient packing of the circuitry inside. These are the company's "entry-level" electronics, but there's nothing cheap about them—the preamp retails for $6900, the amp for $8500—and for all their economical size, they look like luxury goods as well.