Bryston 3B-ST THX Certified Stereo Amplifier

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This is a well-performing vintage amp from Bryston. Bryston is found in studios throughout the world because of its neutrality and reliability. 

This 3B is no exception as it worked admirably on our tech bench without needing a bit of maintenance. 

It's a later version featuring a removable power cord, XLR inputs, and a modern faceplate with solid aluminum handles. Also the power transformers are mounted vertically on the front panel which we like a bit more.

Cosmetically it's very presentable with some occasional scuffs.

And unlike other units we've seen, it does not show any fading or purpling of the black anodized finish.

Click below to add our recommended matching cables from Kimber Kable, all brand new as SkyFi is an official Kimber dealer.

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - BALANCED XLR Connectors - Better

Kimber Kable - BALANCED XLR Connectors - Best

Kimber Kable - Speaker Cables - Better

Kimber Summit Series Monocle XL Speaker Cables (PAIR) - Best

Kimber Summit Series BiFocal XL Bi-Wire Speaker Cables (PAIR) - Best If Applicable 

Kimber Kable - Power Cords - Better

The SkyFi Testing Process for Solid State Amplifiers:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

If the amplifier passes visual inspection, we move on to a controlled power on sequence using a Sencore safety analyzer to monitor current draw in real time. Once the amplifier is determined to be safe to operate, we connect it to full AC mains for function and power testing. We connect the speaker outputs of the amplifier to a Sencore PA81 Power Analyzer which acts as a dummy load, DC offset monitor, and oscilloscope interface. We start with a low level 1KHz test signal at the amplifier’s input and slowly increase its amplitude while monitoring the output on an oscilloscope for signs of noise, clipping, distortion, or improper channel balance. We continue increasing the signal level until the amplifier reaches clipping. At this point we take an output power measurement and compare it to the spec sheet of the amplifier to verify proper performance. If the device under test has both balanced and single ended inputs they are both tested at this time. We finish off the bench evaluation with a 1KHz square wave check and a 20Hz to 20KHz sine sweep to assess the amplifier’s frequency response characteristics. This battery of tests will usually reveal if the amplifier has any issues that need further attention.

Before the device leaves the bench, we perform a listening test with actual music using a variety of preferred test tracks. Our benches are outfitted with familiar monitor speakers which help us identify inconsistencies that will not always show up on our test gear. The main things that we are listening for are hum or noise with no signal present, proper center image, clicks, pops, or any other obvious undesirable audio characteristics.

If the unit passes all of these tests it is moved to our long term testing rig where we simulate real word operating conditions for 6-8 hours. This allows us to monitor the unit for signs of thermal runaway or intermittent issues that only crop up when the unit has fully come up to temperature.

Technical Specifications:

Amplifier Output Class
AB

Rated Power Output
100 Watts Per Channel at 8 Ω
200 Watts Per Channel at 4 Ω
400 Watts In Bridged / Mono Mode at 8 Ω

Frequency Response
20 Hz - 20 kHz

Signal-to-Noise Ratio
100 dB

Crosstalk
Below 100 dB

Total Harmonic Distortion
0.05 %

Intermodulation Distortion
0.025 %

Slew Rate
60 Volts / microsecond

Sensitivity
1.0 Volts

Damping Factor
500 @ 20 Hz

Dimensions (W x D x H)
19" x 9" x 5.25"
[48.26 x 22.86 x 13.34 cm]

Weight
35 lbs.
[15.89 kg]