Bryston 21B Cubed Tri-Mono Power Amplifier

£15,000.00 inc. VAT

Trade-in available.

The powerful Bryston 21B Cubed is a tri-mono power amplifier dedicated to bringing Cubed Series excellence into an easy-to-manage package.

A single 21B3 can also be used to power a single tri-wireable speaker, or any three channels such as the front L-C-R in a home theatre system.

Available in Black or Silver finish, with either 17-inch or 19-inch faceplate.



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With the amazing Bryston 21B Cubed model, we have a multi-channel amplifier dedicated to bringing Cubed Series excellence into an easy-to-manage package.

Each 21B Cubed unit features three channels of premium quality amplification. One is rated at 600 watts, whilst the other two are rated at 300 watts each. Active loudspeaker customers will use the high powered channel for the bass section, and the other two channels for the midrange and high frequency sections of their 3-way systems.

Since the Bryston 21B Cubed is based on the excellent 7B3 and 4B3 amps, it can also be used to power any 3 channels, for instance the front LCR in a home theatre setup.


  • Balanced XLR and single-ended RCA input.
  • 3 channels each, with fully-independent power supplies, including transformers.
  • 600 watts into 8 ohms (and up to 900 watts into 4 ohms) for one channel. Two more channels each rated at 300 watts into 8 ohms and 500 watts into 4 ohms.
  • The patented Salomie circuit, as found in all Cubed Series amplifiers.
  • Switchable gain (23 dB / 29 dB).
  • Fully convection cooled means no noisy fans.
  • Machined and anodised aluminium enclosure and dress panel.
  • Less than 500 mW standby power consumption.
  • SoftStart microprocessor controlled startup sequence – will not trip circuit breakers.
  • DC trigger for automated turn-on and turn-off.
  • Legendary Bryston 20-Year Warranty.


  • Dimensions (Inches): 17 / 19 W x 8.1 H x 16.8 / 18.4 (with front handles) D
  • Weight: 91 lbs / 41 kg
  • Frequency Response: <1 Hz – 100 kHz, -3 dB
  • THD+N (20 Hz – 20 kHz @ Rated Power, 8 Ω): <0.005 %
  • Power Output (per-channel):
    • CH 1 = 600 W @ 8 Ω / 900 W @ 4 Ω
    • CH 2+3 = 300 W @ 8 Ω / 500 W @ 4 Ω
  • Noise: RCA <-115 dB / XLR <-116 dB
  • Input Impedance: Unbalanced 7.5 kΩ / Balanced 5 kΩ / leg


  • Silver or black faceplate.
  • 17-inch or 19-inch faceplate (non-rack mountable).
  • 19-inch versions come with front-mounted handles.

Full Bryston Range Available

Unilet Sound & Vision are official retail partners for Bryston, providing sales, advice and assistance on their entire range of high-quality products. Please do get in touch if you would like a demonstration or wish to purchase.

More Information

Additional information

Weight 41.0 kg
Dimensions 42.67 × 43.18 × 20.57 cm

Black, Silver

Faceplate Size

17-Inch, 19-Inch

Purchase Options

Home Delivery, Click & Collect, Trade-In Available



Bryston is a Canadian company that has been designing and hand crafting state-of-the art electronics for professionals and consumers for over twenty-five years. The company are committed to producing the most accurate and reliable products available, and such is the confidence in their products they still offer a twenty-year warranty on all analogue designs.

PMC has been the proud distributor of Bryston products since 1993, and Bryston's world leading active electronics and amplification feature in PMC’s active loudspeaker systems.

Bryston | Unilet Sound & Vision


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