Bryston 2B SST
C-Series 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 (8-ohm load), unbalanced and balanced inputs:
- 1V sensitivity: 28.4X, 29.1dB.
- 2V sensitivity: 14.3X, 23.1dB.
- Output noise, 8-ohm load, unbalanced input, 1k-ohm input
- 1V sensitivity: wideband - 0.21mV, -82.6dBW / 0.18mV,
- 2V sensitivity: wideband - 0.18mV, -83.9dBW / 0.13mV,
- 1V sensitivity: A weighted - 0.11mV, -88.2dBW / 0.046mV,
- 2V sensitivity: A weighted - 0.10mV, -89.0dBW / 0.032mV,
- Output noise, 8-ohm load, balanced input, 600-ohm input
- 1V sensitivity: wideband - 0.29mV, -79.8dBW / 0.28mV,
- 2V sensitivity: wideband - 0.21mV, -82.6dBW / 0.16mV,
- 1V sensitivity: A weighted - 0.11mV, -88.2dBW / 0.069mV,
- 2V sensitivity: A weighted - 0.10mV, -89.0dBW / 0.040mV,
Power output with 1kHz test signal
- 8-ohm load at 1% THD: 127W
- 8-ohm load at 10% THD: 163W
- 4-ohm load at 1% THD: 213W
- 4-ohm load at 10% THD: 235W
The Bryston 2B SST C-Series is a medium-power solid-state
stereo power amplifier, the lowest-powered unit in Brystons SST C-Series line.
Chart 1 shows the frequency response of the amp with
varying loads. The high-frequency 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 open-circuit, 8-ohm, and 4-ohm loading, is quite low in the audio band. The
usual NHT dummy-load 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 solid-state
power amplifiers. The distortion performance was essentially identical with unbalanced and
Total harmonic distortion plus noise as a function of
frequency at several different power levels is plotted in Chart 3 for 4-ohm 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
power-supply limitations. This didnt happen with the 8-ohm loads at the rated 100W
Damping factor vs. frequency is shown in Chart 4 and is of
a value and nature typical of many solid-state amplifiers, being high up to about 1kHz and
then rolling off with frequency.
The left channel of this unit had somewhat more
power-supply line harmonics due to rectifier conduction-pulse 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 8-ohm loading. As can be seen, the left-channel
spectrum has many line harmonics that extend way up into the test-signal area, whereas the
right-channel spectrum is more normal looking with low amounts of line harmonics and a
tapering-off spectrum of test-signal harmonics.
- Frequency Response of Output Voltage as a Function of Output Loading
Red line: open circuit
Magenta line: 8-ohm load
Blue line: 4-ohm load
|Chart 2 - Distortion as a Function
of Power Output and Output Loading
(line up at 70W to determine lines)
Top line: 4-ohm THD+N
Second line: 8-ohm SMPTE IM
Third line: 8-ohm THD+N
Bottom line: 4-ohm SMPTE IM
|Chart 3 - Distortion
as a Function of Power Output and Frequency
4-ohm 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
5A - left channel
1kHz signal at 10W into an 8-ohm load
5B - right channel
1kHz signal at 10W into an 8-ohm load