The Boulder 2150 mono power amplifier and 2110 stereo preamplifier mark the second time in a few months that I’ve reviewed electronics that define the state of the art in sound quality, design, and luxury. I can recommend both without reservation to anyone who has the money and is looking for superb sound quality.
They do, however, present a challenge to both the reviewer and the audiophile. Here’s the issue: With equipment this good—and this neutral and transparent—almost all of the colorations you hear come from the recording, the front end, the interconnects and speaker cables, the load presented by the speaker, and the complex room interactions that shape the sound of the speaker at a given listening position.
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There is no such thing as a truly neutral and transparent amplifier or preamplifier, but increasingly the inherent sound quality of a small number of elite units has become extremely difficult to gauge due to interactions with more-colored equipment. The question becomes: What are you really reviewing? Even if—as I did—you use a mix of other components, speakers, and listening positions, you can’t avoid the reality that any given reader is going to hear sound that is dominated by the colorations of a different mix of recordings, components, and listening rooms.
This may sound a bit hypothetical, but it was all too clear in practice on the day that the Boulder 2150 mono power amplifier arrived. It literally came in from the cold, and was then thrust immediately into a setup designed for my Pass reference amp. The end result was that the 2150 initially sounded thin and lacking in midrange warmth.
The problem, however, was not in the Boulder. The thinness and lack of warmth came from the fact I was using Transparent Audio speaker cables designed specifically for the radically different loads of Pass amps used with the Wilson Alexias.
The sonic problems that I at first thought were in the 2150 went away the moment I substituted a high-quality AudioQuest speaker cable. They did not exist when Transparent Audio sent me one of its speaker cables specifically configured for the Boulder amps. They also did not exist when I used a high-quality Kimber speaker cable.
The practical problem that did exist, however, was that each speaker cable that worked well in broad terms also changed some aspect of the upper bass and lower midrange, and presented a slightly different soundstage. They were all really good speaker cables, but they changed the sound in ways that were more audible than the colorations of the Boulder 2150.
Much of my initial listening came on a day when Peter McGrath of both Wilson Audio and recording fame was helping me adjust the position of my Alexias. Like my experience with the Pass Xs 300 power amps, the Boulder 2150 has an almost incredible amount of reserve power and an extremely high damping factor. It has an al- most unmatched ability to control speaker loads with the right cable.
What no amp can do, however, is control speaker/room interaction or be precisely designed for a given speaker load.