Power Amplifiers

Bryston 4B SST2 Stereo Power Amplifier

ARTICLE INDEX

Design

I've worked in both the automotive and consumer electronics industries as an engineer for over 15 years. Over that time I've been exposed to more than my share of electronic design. With that in mind, the build quality typically exemplified by Bryston never fails to impress me. Let's take a look 'under the hood' at the 4B SST2 to see why.

Mechanically, the main electronics chassis of the 4B SST2 is constructed of panels of eighth inch thick anodized aluminum. To put it in perspective, the panels are roughly 25% thicker than a quarter (try bending a quarter). You simply don't find this type of heavy duty construction in most if not all consumer electronic products typically found down at the big box retailer. Attached to the sides of the main chassis are massive heat sinks sized to passively cool the amplifier. No fans are used on this big boy to add even a touch of unwanted noise to your system. Bolted to the front of the main chassis is an impressive hunk of half inch thick aluminum. This plate houses a jeweled-style power switch. On my sample this half inch thick panel is also used to rack mount the amplifier.

The back of the chassis contains the inputs, configuration options, and outputs for the amplifier. Both balanced and single ended (RCA type) signal inputs are represented. A magnetic-trip circuit breaker is in place to protect the amp. Configuration switches for remote power up are provided. Switches are also provided to tune the input sensitivity based on the signal input selected. Finally, heavy duty 5-way binding posts are provided for connecting your speaker wire (all the way up to 'garden hose' in diameter). I've used similar WBT binding posts in some of my projects and these posts alone can be quite costly.

Bryston 4B SST2 C-SERIES

The only disappointing detail on the mechanical build was Bryston's decision to mount the RCA inputs directly to a circuit board without mechanically connecting the input to the amps' chassis. Every insert of an audio cable will unnecessarily stress the circuit board. In fact, if someone is ham-fisted enough I could see a crack developing. In typical use this should not be a big deal; however, the design is not as bullet proof as the rest of the other signal inputs and outputs which are mounted directly to the chassis.

Electronically, the Bryston 4B SST2 is a dual mono design (go ahead and check the schematic on Bryston's web site to confirm if you wish!). This basically means that there are two independent amplifiers housed in the single chassis. The dual mono design can be clearly seen in the photo.

Bryston 4B SST2 C-SERIES

Notice the two toroidal power transformers (the 'donuts') top and center feeding mirror copies of the remainder of the amplification circuitry. An individual copy of the amp components (as would be typical in lower end products) ensures that each channel of amplification works independently of the other. Musical peaks in the left channel do not steal power from the right channel and compromise dynamics. Moreover, music won't bleed through (or crosstalk) from one channel to the other smearing and compromising the sound. In sum, this design can lead to better musical reproduction - especially when the amplifier is pushed hard.

Somehow, I doubt this dual design would be an Energy Star approved green solution since it consumes 170 Watts at idle and up to 2100 Watts at full throttle, but sometimes you can't compromise if you want top performance. In a nod to the environment, I'd recommend using a switched power outlet to prevent any parasitic power draw.

Power from the 50 pound 4B SST2 is rated at two 300 Watts channels into 8 Ohm load (i.e. a speaker), two 500 Watts channels in 4 Ohm load, or a massive 900 Watts in to a single 8 Ohm load. While Bryston itself offers more powerful (and expensive) amplifiers, the 4B SST2 power capacity should be more than adequate for most users.

The damping factor of the 4B SST2 is over 500 at 20 Hz. What does this mean? Let me try to simplify with an analogy. When you try to stop a Corvette ZR1 with high performance brakes, it stops – now. Like the Corvette, when the Bryston puts on the brakes, the speaker stops – now. Based on the rated damping factor, the Bryston should tightly control the movement of the speakers – especially with respect to bass reproduction. This tight control should be heard as quick transients in bass. A quick slap of a drum in a recording will be a quick slap of a drum reproduced by the speaker. Not a slap followed by a decaying echo as a poorly designed amplifier struggles to control the speaker driver.