Bryston 4B Cubed Amplifier

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The Bryston 4B³ is a dual channel (stereo) amplifier internationally acclaimed as being suited for the finest and most sophisticated sound systems.

It is Bryston's most popular Cubed Series model winning SoundStage Network's 2017 Products of the Year Award.

Ask About Our Trade Up Program

Just because it has a 20-year warranty doesn't mean you have to keep it that long. (But you can, if you want.)

Trade in your vintage 4B (up to SST² Series) for a discount on the newest version of an iconic piece of the audiophile landscape. Bryston's modern Cubed Series features higher power, lower noise, dramatically lower distortion, and is even more rugged than the classic 4B you've owned for years.

We'll take back any working 4B up through the SST² series as long as it's in good cosmetic condition. It doesn't have to be perfect - nicks and dings are OK, but no major scratches on the dress panel, and no bent metal. US and Canada only.

Ask for a Trade up

"The 4B³ is a control freak in terms of grabbing hold of your speakers' drivers and maintaining bass control, depth and power."

Edgar Kramar, Audio Esoterica

"These dig right to the heart of the music and result in one of the best all-round power amplifiers I have encountered at this price."

Adam Smith, Hi-Fi News & Record Review


  • Inputs: 2x Balanced Inputs (XLR or TRS), 2x Single Ended Inputs (RCA)

Power Capabilities

  • 300W into 8Ω
  • 500W into 4Ω
  • 900W into 8Ω (Bridged Mono)


  • Active extremely low distortion input buffer
  • Balanced and Single Ended audio inputs
  • Selectable gain at 23 or 29dB
  • Regulated power supplies to all voltage gain stages
  • Independent power supplies for each channel
  • Convection cooled and housed in a fully aluminum chassis.
  • No fans or other moving parts
  • Bridging switch configures amplifier into a single 900W Channel


  • Available with silver or black faceplate (3U + .55”)
  • 17” (without handles) or 19” (with handles) faceplate available (non-rack mountable)
  • Rack mountable Pro Edition available in black (see Cubed Pro for more details)

First to Last Watt Philosphy

A significant part of the design criteria for the new Cubed series was to develop amplifiers that would maintain an ideal power curve from the first watt to the last. Most amplifiers exhibit a power curve where the best noise floor, drive capability and distortion are acheived from about 1/3 power and up. The new Bryston Cubed series amplifiers maintain their ideal power curve starting right from the first watt.

Achieving this starts with a number of design approaches:

  1. Complete freedom from low-level crossover, zero-crossing, artifacts

    Most class-AB amplifierrs have sufficient bias to prevent primary crossover distortion, but secondary crossover distortion is caused by insufficient speed in the driver transistors. The Cubed Series uses very fast drivers to help prevent this, as well as proprietary technology. Bryston's Quad Complementary Output design vastly reduces the capacitance seen by the driver transistors, virtually eliminating storage delay in the output stage that could contribute to nonlinearities in the zero-crossing region.

  2. Continuing efforts to reduce low-level noise. The clarity of level noise

    The clarity of Bryston's designs is enhanced at low listening levels by pushing the noise floor far below the signal level, improving the silence between the notes and enhancing the clarity of the music at low power levels.

  3. Concentration on reducing distortion at all levels, especially high frequencies

    Bryston amplifiers are perhaps the only designs to concentrate so much effort at reducing HF distortion artifacts, and the results are remarkably flat THD-with-frequency curves, sho frequency curves, sho frequency curves, showing almost no tendency to wing almost no tendency to increase distortion as frequency rises. This has the effect of reducing overall haze, helping to pull the quietest passages out of the background.

Additionally, the new Cubed Series employs highly effective RF employs highly effective RF rejection in the power supplies, which traps and eliminates radio-frequency hash from either interfering with or emanating from the amplifier via the power cable or signal cables.

Press and Reviews

Bryston Magazine Guide
Bryston Magazine

Guides & Advice
by Moon Audio


General Features

Harmonic Distortion
≤.005% from 20Hz to 20kHz at 300W
Noise below full output
-110dB single ended, -113dB balanced
Slew Rate
Power Bandwidth
.5Hz to >100kHz
Damping Factor
>500 at 20Hz (8Ω)
Switchable Gain
23dB or 29dB