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What You Need to Know
What Is This Product and What Does It Do?
The Bryston 4B³ is a stereo power amplifier. (Bryston says it “4B Cubed.”) Its job is simple: take a small music signal from your preamp and make it strong enough to drive a pair of speakers.
Power-wise, the 4B³ puts out 300 watts per channel into 8-ohm speakers. If your speakers are 4 ohms, it gives you 500 watts per channel. You can also run it as a single-channel “bridged” amp — useful later if you add a second 4B³.
Bryston has been building amps in Ontario, Canada since the early 1970s. Their gear shows up in recording studios and radio stations all over the world. The 4B has been made nonstop since the late 1970s. This “Cubed” version is the sixth generation.
The big upgrade in the Cubed line is the patented Salomie input circuit. Bryston developed it with Dr. Ioan Alexandru Salomie. It blocks the kind of stray noise modern homes create — think Wi-Fi, cell signals, and switching power supplies.
The 4B³ is a Class A/B amp. Class A/B means it runs in pure Class A — the cleanest mode — for the first few watts. Then it shifts to a more efficient mode for bigger power demands. Most listening stays in the clean Class A range.
The amp is also “dual-mono.” That means the left and right channels each have their own power supply and transformer. The only thing they share is the wall plug. One channel under heavy load — a big drum hit, a deep bass note — can’t steal power from the other.
Bryston backs the 4B³ with a 10-year warranty on parts and labor. The warranty is for the first-time buyer only — it does not transfer to a new owner.
What Are Reviewers Saying?
Roger Kanno’s review earned the 4B³ a place on SoundStage!’s Recommended Reference Components list. He said he was “blown away” by how clear and in control the amp sounded. He called the reproduction nearly flawless and named it a “benchmark for performance and value.”
Maurice Jeffries praised the new Salomie input stage. He said the top end was among the sweetest and purest he had heard from a solid-state amp near this price. He also noted the amp’s strong grip on the bass and low noise floor. His take: “one helluva performer.”
Jason Kennedy called the 4B³ a “masterful and superbly executed” amplifier. He liked its control, frequency extension, and even-handed sound. He recommended it to anyone shopping in the category. He closed by saying he’d be sorry to see the review unit go back.
Who Is This Best For?
Your speakers need a lot of power to sound their best — big floor-standers, hard-to-drive 4-ohm models, or anything that’s power-hungry.
You’re putting together a serious two-channel music system and want an amp you can keep for decades.
You care where your gear comes from. Bryston amps have been used in studios and radio stations for over 40 years — and you want that pedigree at home.
You’re moving up from an integrated amp to separates and want a top-notch power amp without paying flagship prices.
You like the idea of hand-built gear from Canada — and a factory test sheet in every box.
How Does It Connect to Your System?
The 4B³ takes a signal from any preamp or home theater processor with a volume control. Each channel has two input options: balanced (XLR or TRS) and unbalanced (RCA). A rear-panel switch picks between them.
Balanced inputs are best for long cable runs and systems where you want the lowest possible noise. RCA is the normal home audio connection and works great for shorter runs.
For speakers, the 4B³ has heavy-duty binding posts. They accept spade lugs, banana plugs, or bare wire.
A low-voltage DC trigger on the back lets the amp turn on by itself when you power up a matching preamp. Handy if the 4B³ lives in a rack or behind a cabinet.
You can also choose between two gain settings — 23 dB or 29 dB. That lets you match the amp to your preamp so you’re not stuck running the volume control at the extremes.
One thing to keep in mind: the 4B³ is a power amp only. You’ll need a separate preamp — like Bryston’s BP-17³ — or an integrated amp with preamp outputs. Not sure what you need? Give us a call at 800-942-0220 and we’ll help.
Earned Recognition
Few amps at the 4B³’s price have earned this much recognition from the audio press. Here’s a quick summary of the awards this amp has won.
Category: Stereo Power Amplifiers
SoundStage!’s Recommended Reference Components list is reserved for gear the editors see as benchmarks in their category.
Category: Power Amplifiers
NOVO (formerly Canada HiFi) gives Product of the Year awards to components its reviewers single out as the year’s standouts.
Category: Power Amplifiers
Hi-Fi Advice’s HFA award goes to components the site considers top performers it can recommend without hesitation.
Category: Stereo Power Amplifiers
Part-Time Audiophile’s yearly Buyers Guide points readers toward products the editors recommend in each category.
Pairs Well With
Building your system? Here are some great companions for the 4B³:
- A preamp — required. The 4B³ is a power amp only. Bryston’s own BP-17³ Cubed preamp is the natural match. Any preamp with line-level outputs (balanced or RCA) will work. Shop preamplifiers »
- Speaker cables. A high-power amp like the 4B³ is worth pairing with a good speaker cable. Shop speaker cables »
- Balanced (XLR) interconnects. For the preamp-to-amp connection, balanced cables are the preferred choice. Shop XLR interconnects »
- Power conditioning. Clean power helps every piece of gear in your system. Shop power conditioners »
- Digital source. A quality DAC or music streamer brings the 4B³’s clarity to your digital music. Shop digital audio »
Features & Specifications
Amplifier Performance
Plenty of Power — The 4B³ puts out 300 watts per channel into 8-ohm speakers and 500 watts per channel into 4 ohms. Bridged to mono, it delivers 900 watts into 8 ohms. That’s enough headroom for just about any speaker, even in a large room.
Very Low Distortion — Total harmonic distortion plus noise stays below 0.005% from 20 Hz to 20 kHz at rated power. In plain English: the amp reproduces your music almost exactly as the preamp sends it — no added color.
Wide Bandwidth — The amp is flat from below 1 Hz to 100 kHz (at –3 dB). That means it has room to spare above and below what you can hear.
Strong Speaker Control — A damping factor above 500 at 20 Hz into 8 ohms gives the 4B³ a tight grip on the woofer. That matters on deep bass notes and big dynamic swings.
Topology & Design
Dual-Mono Build — Each channel has its own power supply and transformer. The only shared part is the power cord. One channel under heavy load can’t affect the other.
Patented Salomie Input Circuit — Bryston developed this circuit with Dr. Ioan Alexandru Salomie. It uses 12 parts in a special layout and handles the first 6 dB of gain. Bryston says its distortion is less than 1/1000th of 1%. It was also built to block RF and EMI noise.
Quad-Complementary Output Stage — Bryston’s output design is built to give you the sound character of a Class A amp — but with the efficiency and reliability of Class A/B.
No Fans, No Noise — The 4B³ is fully convection cooled. The chassis acts as a big heatsink, so there are no fans or moving parts to wear out or hum.
Connectivity
Balanced and RCA Inputs — Each channel has XLR (balanced), TRS, and RCA (unbalanced) inputs. A rear-panel switch picks between them.
Switchable Gain (23 dB or 29 dB) — Match the amp’s sensitivity to your preamp. That keeps your volume control out of the extremes.
DC Trigger — Connect a matching preamp (or any 5–12 V source) and the 4B³ turns on with the rest of your system.
SoftStart Turn-On — A microprocessor brings the amp up gently at power-on. That keeps the inrush current from tripping a breaker.
Build & Finish
Hand-Built in Canada — Every 4B³ is put together at Bryston’s Ontario factory. Each one runs through 100 hours of burn-in before it ships. And every unit includes a printed test sheet showing how your specific amp measured.
Black, 17-Inch Faceplate — This SKU is the black model with the 17” front panel (non-rack-mount, no front handles). The 19” version with rack handles is sold separately.
Power & Warranty
Low Idle Draw, Big Output — Standby draw is under 500 milliwatts. Idle draw is about 70 watts. At full stereo output the amp pulls around 1000 watts. Bridged into 900 W, up to 1700 watts.
10-Year Factory Warranty — Bryston covers the 4B³ for 10 years against factory defects. Parts and labor are both included. The warranty is for the first-time buyer only and does not transfer. Save your bill of sale, or register your purchase on bryston.com.
Quick-Reference Specifications
| Amplifier Class | Class A/B (Quad-Complementary output) |
| Power Output (stereo) | 300 W per channel (8 Ω); 500 W per channel (4 Ω) |
| Power Output (bridged mono) | 900 W (8 Ω) |
| THD+N (20 Hz–20 kHz, rated power, 8 Ω) | < 0.005% |
| Frequency Response | < 1 Hz – 100 kHz (–3 dB) |
| Noise (input shorted) | RCA: –112 dB | XLR: –117 dB |
| Gain (switchable) | High: 29 dB | Low: 23 dB |
| Input Impedance | Unbalanced: 7.5 kΩ | Balanced: 30 kΩ (+) / 6 kΩ (–) |
| Damping Factor | > 500 at 20 Hz, 8 Ω |
| Inputs | Balanced XLR/TRS & single-ended RCA (rear-panel input select) |
| Trigger | Low-voltage DC trigger input |
| Cooling | Fully convection cooled (no fans) |
| Power Consumption | Standby < 0.5 W | Idle ≤ 70 W | Full stereo ≈ 1000 W | Bridged ≈ 1700 W |
| Dimensions (H × W × D) | 6.3 × 17 × 15.5 in | 160 × 432 × 394 mm |
| Weight | 42 lb | 19 kg |
| Finish | Black dress panel, 17” wide (non-rack-mount) |
| Warranty | 10 years parts & labor, non-transferable (Bryston) |
| Country of Origin | Hand-built in Canada |
Frequently Asked Questions
What else do I need to use the Bryston 4B³?
The 4B³ is a power amp only. You’ll need a separate preamp to send it a signal — or an integrated amp that has preamp outputs. Bryston’s BP-17³ Cubed is a great match. You’ll also need a pair of speakers and speaker cables. Want help building a full system? Call us at 800-942-0220.
Is the 4B³ a good match for my speakers?
Matching an amp to your speakers comes down to power, sensitivity, and impedance. The right answer depends on your speakers and your room. Our team does this kind of match every day. Give us a call at 800-942-0220, weekdays 9am–6pm EST, and we’ll help you figure it out.
What are the differences between Class A, Class A/B, and Class D amps?
Class A amps keep their transistors fully “on” at all times. That’s very clean sound but not very efficient. Class A amps run hot and use a lot of power, even at idle.
Class A/B amps — like the 4B³ — run in pure Class A at low power, then switch to a more efficient mode when you turn it up. This is the most common design in high-end audio. It balances clean sound, strong power, and reasonable efficiency.
Class D amps use fast switching to run very efficiently. They run cool and can be small. Modern Class D designs from good makers sound excellent — it’s just a different way of doing the job than Class A/B.
Can the 4B³ be bridged to mono?
Yes. In bridged mono mode, a single 4B³ puts out 900 W into 8 ohms. If you later want to run a pair of monoblocks, you can add a second 4B³ and bridge both. A switch on the rear panel picks between stereo and bridged mode.
What’s the difference between the 17-inch and 19-inch versions?
The amp inside is identical either way. The 17” model (this one) has a clean faceplate and is the standard pick for most audio systems. The 19” model adds rack-mount handles on the front, which makes it 1.6 inches deeper. Pick the 19” if you’re mounting it in an equipment rack. Otherwise, go with the 17”.
How does the 4B³ compare to the 3B³ and 7B³?
The 3B³ is the smaller model — 200 W per channel into 8 ohms. The 4B³ is the sweet spot for most two-channel systems. The 7B³ is a monoblock (you’d need two) at 600 W into 8 ohms, for big rooms or very demanding speakers. Torn between models? Give us a call.
What does the Bryston warranty cover?
Bryston covers the 4B³ for 10 years against factory defects. Parts and labor are both included. The warranty is for the first-time buyer only and does not transfer. Save your bill of sale, or register your purchase on bryston.com — coverage requires proof of purchase from an authorized dealer.
Does the 4B³ run hot?
The 4B³ cools itself with no fans — the chassis acts as a big heatsink. At idle, the amp draws about 70 watts and stays just warm to the touch. Push it hard and it warms up, like any high-powered amp. Leave a few inches of clearance above and on the sides for airflow.
What’s in the Box
- Bryston 4B³ Stereo Power Amplifier (Black, 17” faceplate)
- Detachable IEC power cable
- Factory test sheet (matched to your amp’s serial number)
- Owner’s manual
- Warranty and registration info
Packing contents may vary by region and revision. If you need a specific item confirmed before you buy, give us a call at 800-942-0220.
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