July 2008
Bryston 2B SST
CSeries Amplifier: Measurements
All amplifier measurements are performed
independently by BHK Labs. Please click to learn
more about how we test amplifiers there. All measurement data and graphical
information displayed below are the property of SoundStage! and Schneider
Publishing Inc. Reproduction in any format is not permitted.
 Measurements were made at 120V AC line voltage with both
channels being driven. Measurements made on the left channel and the unbalanced inputs
unless otherwise noted.
 This amplifier does not invert polarity.
 AC line current draw at idle: 0.37A.
 Input impedance @ 1kHz: 9.9k ohms.
 Output impedance at 50Hz: 0.026 ohms.
 Input sensitivity for 1W output into 8 ohms:
 1V sensitivity: 99.6mV
 2V sensitivity: 197.8mV
 Gain (8ohm load), unbalanced and balanced inputs:
 1V sensitivity: 28.4X, 29.1dB.
 2V sensitivity: 14.3X, 23.1dB.
 Output noise, 8ohm load, unbalanced input, 1kohm input
termination, Lch/Rch:
 1V sensitivity: wideband  0.21mV, 82.6dBW / 0.18mV,
83.9dBW
 2V sensitivity: wideband  0.18mV, 83.9dBW / 0.13mV,
86.8dBW
 1V sensitivity: A weighted  0.11mV, 88.2dBW / 0.046mV,
95.8dBW
 2V sensitivity: A weighted  0.10mV, 89.0dBW / 0.032mV,
98.9dBW
 Output noise, 8ohm load, balanced input, 600ohm input
termination, Lch/Rch:
 1V sensitivity: wideband  0.29mV, 79.8dBW / 0.28mV,
80.1dBW
 2V sensitivity: wideband  0.21mV, 82.6dBW / 0.16mV,
85.0dBW
 1V sensitivity: A weighted  0.11mV, 88.2dBW / 0.069mV,
92.3dBW
 2V sensitivity: A weighted  0.10mV, 89.0dBW / 0.040mV,
97.0dBW
Power output with 1kHz test signal
 8ohm load at 1% THD: 127W
 8ohm load at 10% THD: 163W
 4ohm load at 1% THD: 213W
 4ohm load at 10% THD: 235W
General
The Bryston 2B SST CSeries is a mediumpower solidstate
stereo power amplifier, the lowestpowered unit in Bryston’s SST CSeries line.
Chart 1 shows the frequency response of the amp with
varying loads. The highfrequency response is moderately wide with an approximate 3dB down
point of 100kHz. Output impedance, as judged by the closeness of spacing between the
curves of opencircuit, 8ohm, and 4ohm loading, is quite low in the audio band. The
usual NHT dummyload curve is not shown as the variations in the response would not
display. The variation with the NHT dummy load in the audio range is of the order of
+/0.05dB  a negligible amount.
Chart 2 illustrates how total harmonic distortion plus
noise vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load. The
amount of distortion is low right up to clipping  the behavior of most solidstate
power amplifiers. The distortion performance was essentially identical with unbalanced and
balanced connections.
Total harmonic distortion plus noise as a function of
frequency at several different power levels is plotted in Chart 3 for 4ohm loading. The
amount of rise in distortion at low and high frequencies is admirably low, except at the
180W level where distortion started to rise abruptly below 20Hz, most likely due to
powersupply limitations. This didn’t happen with the 8ohm loads at the rated 100W
power output.
Damping factor vs. frequency is shown in Chart 4 and is of
a value and nature typical of many solidstate amplifiers, being high up to about 1kHz and
then rolling off with frequency.
The left channel of this unit had somewhat more
powersupply line harmonics due to rectifier conductionpulse ground currents than the
quieter right channel. Therefore, the spectrum of both channels is shown in charts 5A and
5B for a 10W 1kHz test signal with 8ohm loading. As can be seen, the leftchannel
spectrum has many line harmonics that extend way up into the testsignal area, whereas the
rightchannel spectrum is more normal looking with low amounts of line harmonics and a
taperingoff spectrum of testsignal harmonics.
Chart 1
 Frequency Response of Output Voltage as a Function of Output Loading 
Red line: open circuit
Magenta line: 8ohm load
Blue line: 4ohm load
Chart 2  Distortion as a Function
of Power Output and Output Loading 
(line up at 70W to determine lines)
Top line: 4ohm THD+N
Second line: 8ohm SMPTE IM
Third line: 8ohm THD+N
Bottom line: 4ohm SMPTE IM
Chart 3  Distortion
as a Function of Power Output and Frequency 
4ohm output loading
Grey line: 180W
Cyan line: 100W
Blue line: 30W
Magenta line: 10W
Red line: 1W
Chart 4  Damping Factor
as a Function of Frequency 
Damping factor = output impedance divided into 8
Chart 5  Distortion and
Noise Spectrum 
5A  left channel
1kHz signal at 10W into an 8ohm load
5B  right channel
1kHz signal at 10W into an 8ohm load
