Bryston, based in Peterborough, Ontario, Canada, has been around since 1961. The company straddles the border between pro audio and the part of the audiophile/home theater world that gravitates to uncolored/accurate sound quality from precision solid-state equipment. Bryston amps have also been used in installation sound and touring rigs over the years because they tend to be built like tanks, include overload/overheat protection, and feature lengthy warranty periods.
The 4B3 Pro (known as 4B cubed) power amp is aimed at the higher end recording or mastering studio, and built to power any sized speaker to whatever SPLs are desired. It's a modern, I would say better-sounding, version of the power amps that used to sit in racks in a closet and run big, soffit-mounted monitors in the control rooms of yore. In other words, high-power, heavy, built to withstand years in a rack and made to function, and sound the same every time it's turned on and signal is applied.
The Pro versions of Bryston's power amps feature black anodized aluminum front panels, with built-in rackmount ears and heavy-duty lifting handles, plus individual channel level trimmers on the rear panel. Specs say 300 W per channel into 8 ohms, 500 W into 4 ohms, 900 W into 8 ohms in the bridged-mono setup. There are two gain settings, +29 dB/28.8 V for lower-level/consumer-level inputs, and +23 dB/14.14 V for pro-level inputs, like the output of a big console's monitor section. Gain is switched on the back panel, as is the choice of balanced XLR or unbalanced RCA input. Measured distortion, IMD and THD+N, are in the 0.005% range, and the noise floor is below -110 dB (i.e., inaudible). My review unit, serial number 001402, came with its own "final checkout" measurements, with all specs meeting or exceeding the published averages.
So, what do all the numbers mean? For one thing, the amp runs dead silent. It has no cooling fans or other mechanical parts that make noise. You can put it right on the table next to you, drive whatever speakers to whatever levels, and never hear anything from the amplifier. That said, it's a big, heavy monster, so you probably want it in a rack somewhere. It requires a bit of airflow to move heat off the big cooling fins on its side. The top panel is vented too, and not intended to be covered.
Back to the sound qualities: The amp's high power and vanishingly low distortion specs mean it's providing a bunch of gain to whatever sound you throw at it, and that's it. All amps have some kind of "sound" because there are a certain number of parts in a circuit, and so far we don't have a straight wire with gain (although the Benchmark AHB2 power amp I reviewed [Tape Op #111] is as close as I've ever heard). At its core, the Bryston 4B3's sound is big and mighty, but not overhyped. Especially in the low end, I felt like there is no recorded sound that this amp can't pass on with gain to my speakers, and then it's up to the speakers to move the air. To my ears, the midrange was fast and accurate, uncolored, and the treble was definitely not hyped, but it was right there in your face if the recording was made that way.
The build quality of this amp is unlike any other amp I've had, except for my old Aragon 8004. These amps are the modern, technologically up-to-date version of the heavy-metal, high-powered Class AB solid-state power amps, akin to the big McIntosh and Phase Linear amps of the past. Unlike the older amps, newer technologies of design and available components have advanced to where super-clean power with a dead-silent noise floor is both practical and expected. We live in a golden era of power amps, ones capable of driving big speakers moving a lot of air, even as many studios move to small-format, self-powered speakers. The audiophile world, too, is moving toward smaller speakers and, in a big way, toward headphone systems. So, these big-iron amps may be dinosaurs walking the earth. Get 'em while they're here.
To evaluate the Bryston, I first hooked it up to my Amphion Two18 [#108] studio monitors, swapping out my Benchmark AHB2 power amp. I didn't hear much difference, especially when the two amps' gain settings were matched. Maybe the Bryston was a tiny bit meatier in the low end. I went on to do some signal processing and other DSP work in the computer and source-digitizing from tapes. Everything turned out as planned, so for whatever differences in sound quality there were, the Bryston did its job and told me the truth.
Where the Bryston really shined was driving my big B&W 808 speakers in my large living room, which has a cathedral ceiling and is laid out with plenty of space for the speakers to move air and fully develop imaging. I swapped out the Hafler P3100 power amp [I reviewed in #127], which had no problem driving these speakers as loud as I'd ever want to hear them (they were designed to produce ear-damaging SPLs without breaking up). The Bryston sounded like the audio equivalent of a big, long convertible Coupé de Ville; not extending any big effort to make those speakers move whatever air I'd want to move. For those who do want to listen to big speakers very loud, these will do the job and never sweat. Sound-wise, I'd say the Bryston made the B&Ws sound a degree or two more cool and objective than the Hafler, probably a touch less color in the midrange and more authority in the deep bass. I assume this has to do with more power in reserve being able to act a bit more quickly in making the woofer engine move the air. Given that the Bryston costs more than three times the Hafler, I'd expect it to drive big speakers more confidently. I also think a big part of what you're buying with the Bryston is indestructible, ironclad build quality, and an included 20-year warranty. Basically, the Bryston is military spec at a commanding price point.
The potential buyer of this amp is someone who must have a fail-safe monitor system, like a mastering room where every second of downtime is dollars evaporating into the air. Or one of the few remaining big studios, where non-working control room monitors during a session involving union-scale musicians is not an option (such as a movie production soundstage). For a smaller-scale operation, it offers an aspiration-level option for your monitor amp, something you'll buy once, and never worry about again. If that's your goal, definitely work out a no-fault trial period so you're sure this kind of naked honesty is the brand of sound you really want. This amp will make your speakers tell the truth as much as they are able, and with a firm hand.