Усилители мощности моно — Bryston 28B Cubed

The 28B Cubed (28B³) is the most powerful mono amplifier from Bryston, the Canadian company that has built professional and home amplifiers since the 1970s. It sits at the top of Bryston's Cubed Series, which introduced a new patented input circuit across the range, and is sold individually, so a stereo system needs two. Each unit is hand-built in Canada and ships with a serial-numbered measurement sheet documenting its own performance.

Key specs that matter

The 28B³ delivers 1,000W into 8 ohms and 1,800W into 4 ohms. Frequency response extends from below 1Hz to 100kHz (-3dB), THD is below 0.005% from 20Hz to 20kHz at rated power into 8 ohms, and noise is -117dB through the balanced input and -116dB through the unbalanced input. A rear switch chooses between the XLR and RCA inputs, and two pairs of binding posts are provided. The power supply combines a large dedicated toroidal transformer with 160,000uF of filter capacitance. Standby consumption is below 500mW. Each amplifier weighs 42kg, with a 17-inch faceplate or a 19-inch faceplate with machined front handles, in black or silver.

Engineering and use context

All Cubed Series amplifiers use an input stage developed with the late Dr Ioan Alexandru Salomie. This patented circuit uses about a dozen active devices as a highly linear buffer that provides the first 6dB of gain, matches the amplifier to almost any preamplifier and keeps its own distortion below 0.001%. It also traps noise and radio-frequency interference before they reach the power stage. The output stage uses a quad-complementary configuration, sharing current across many output devices so the amplifier can deliver its full rating into low impedances. Bryston's first watt to last watt philosophy aims for the same low distortion at low listening levels as at full power. The amplifier is entirely convection-cooled with no fans, so it runs silently, and the enclosure and front panel are machined and anodised aluminium. A microprocessor-controlled SoftStart sequence limits inrush current so a pair can run on a standard domestic circuit without tripping breakers, and a DC trigger switches the amplifiers on and off with the preamplifier.

Pairing

Each 28B³ can sit next to its speaker, fed from the preamplifier by a long balanced XLR cable while keeping speaker cables short. Its current reserves suit large, low-sensitivity loudspeakers and difficult loads such as electrostatics and large ribbon designs in big rooms. Heatsinks need open space around them.

Alternatives

Bryston's own 7B Cubed is a smaller mono amplifier in the same series for rooms and speakers that need less power.