Solid State Power Amp Reviews

Launched in 1967, Quad's highly original, elegantly styled 33 preamplifier and 303 power amplifier were Quad's first all–solid state designs and among the first solid state separates. The 303 may have been one of the first "vertical" amplifiers. Together with the 405 stereo amplifier, which came out in 1975, and the FM2 and FM3 tuners, these products proved to be enduring, widely feted successes from their launch until they were discontinued, the 33 in 1982, the 303 in 1985. Meanwhile, they enjoyed massive production runs, were marketed worldwide, and were much admired for their modern industrial design. It's said that Quad sold 120,000 33 preamps and 100,000 303 amplifiers. Across two versions, the 405 sold even more.

Quad introduced new versions of the 33 and 303 (each component $1599) in 2024, apparently moved to do so by the continuing hot market for originals.

Woot, woot! I was thrilled when I saw the announcement for this amplifier. I was tempted to order one sight unseen and sound unheard. Why? First off, it employs the newest (as of March 2025) class-D amplification technology. Second, it can accommodate all sorts of audio systems, from an eight-channel surround setup to a megalomaniacal two-channel stereo system. Third, the specs, even in the context of its technology, are impressive. And fourth, I can lift it by myself—easily! How can I pass this amplifier up?

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!"

It is unusual to begin a review with a detailed discussion of setup. But setup protocol for the Moon 861 power amplifier ($22,000 each), the top-level amplifier in the North Collection from Moon, which I reviewed bridged in mono, proved crucial to its sound.

The setup saga began when Moon co-owner Costa Koulisakis traveled to Port Townsend from Quebec to help remove two 861 amplifiers from their sturdy flight cases and set them up.

It's important for readers to remember that I've spent my adult life as an artist and mechanic. Making things. Working as a tradesperson during the day then at an easel or workbench at night.

When I finished high school, all I wanted to do was work in a fancy, well-equipped shop building drag race engines. Engine building was something I had already shown a talent for, but my parents insisted I go to college. Unfortunately, my high school grade point average was so low I was turned down by every college I applied to. Consequently, my parents forced me to attend Wright Junior College in Chicago, a place where teachers rolled joints for their students. And I got straight A's. Those easy A's got me into Western Illinois University, a small state college in a tiny rural town called Macomb near the Mississippi River. My mother was so proud, she told everybody she knew that her son was accepted into "university," but she could never remember which one.

Throughout my hundred years, I've told everyone who'd listen: If it's adventure you seek, the best way to find it is to stand on the right corner at the right time wearing the right hat, and when the limo pulls up and the driver says, "Get in," do not ask where it is going.

This strategy has served my life story well. It has placed me without striving in countless cinema-worthy locations, hanging with all types of legend-worthy characters.

Lately, that corner where I stand wearing the right hat is in front of the Polish newsstand at the intersection of Manhattan and Greenpoint Avenues in Brooklyn.

There was a period in the 1970s when many pop ballads that should have had understated arrangements instead turned grandiose and even maudlin. Take Gilbert O'Sullivan's sensational single "Nothing Rhymed" (a track that went deep for a pop hit, referencing famine, duty, and morality). Soon after the start, O'Sullivan's piano is overshadowed by a loud, saccharine string section.

Another example is "Lotte," German singer Stephan Sulke's portrayal of a dying love affair. The devastatingly wistful chanson is burdened by a mawkish orchestral track—the equivalent of glitterbombing an Edward Hopper painting.

Contrast this with Roberta Flack's definitive version of Ewan MacColl's "The First Time Ever I Saw Your Face." Apart from Flack's voice and her emotional delivery, the gently strummed guitar and quiet piano do all the heavy lifting. An unhurried double bass and a couple of minimally bowed string instruments leave swaths of negative space, helping to give her interpretation its hushed, reverent character.

I reflected on all this after spending several months with Balanced Audio Technology's REX 500 solid state power amplifier ($25,000), which has more in common with the Roberta Flack track than with the bombast of "Nothing Rhymed."