All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.
Notes: Measurements were made at 120V AC line voltage with both channels being driven. Measurements were made on the left channel in the stereo mode unless otherwise noted.
Power output (stereo mode)
 Power output at 1% THD+N: 117.5W @ 8 ohms, 209.5W @ 4 ohms
 Power output at 10% THD+N: 146.5W @ 8 ohms, 270.0W @ 4 ohms
Power output (mono mode)
 Power output at 1% THD+N: 405.4W @ 8 ohms, 671.0W @ 4 ohms
 Power output at 10% THD+N: 504.2W @ 8 ohms, 820.0W @ 4 ohms
Additional data
 This amplifier does not invert polarity.
 ACline current draw at high bias: 1.63A, 0.71PF, 138W
 ACline current draw at low bias: 0.92A, 0.72PF, 81W
 Gain: output voltage divided by input voltage, 8ohm load
 Low bias
 Stereo balanced inputs: (Lch/Rch): 23.3X, 27.4dB / 23.2X, 27.3dB
 Stereo unbalanced inputs (Lch/Rch): 31.6X, 30.0dB / 31.3X, 29.9dB
 Mono balanced input: 22.2X, 26.9dB
 Mono unbalanced input: 30.4X, 29.7dB
 High bias
 Stereo balanced inputs: (Lch/Rch): 23.8X, 27.5dB / 23.7X, 27.5dB
 Stereo unbalanced inputs (Lch/Rch): 32.2X, 30.2dB / 32.0X, 31.1dB
 Mono balanced input: 23.0X, 27.2dB
 Mono unbalanced input: 31.6X, 30.0dB
 Low bias
 Input sensitivity for 1W output into 8 ohms
 Low bias
 Stereo balanced inputs: (Lch/Rch): 121.4mV / 121.9mV
 Stereo unbalanced inputs (Lch/Rch): 89.5mV / 90.4mV
 Mono balanced input: 127.4mV
 Mono unbalanced input: 89.5mV
 High bias
 Stereo balanced inputs: (Lch/Rch): 118.8mV / 119.3mV
 Stereo unbalanced inputs (Lch/Rch): 87.8mV / 88.4mV
 Mono balanced input: 123.0mV
 Mono unbalanced input: 89.5mV
 Low bias
 Output impedance @ 50Hz
 Stereo lowbias mode: 0.279 ohm
 Stereo highbias mode: 0.180 ohm
 Mono lowbias mode: 0.571 ohm
 Mono highbias mode: 0.375 ohm
 Input impedance @ 1kHz
 Stereo balanced inputs: 10.3k ohms
 Stereo unbalanced inputs: 67.2k ohms
 Mono balanced input: 3.6k ohms
 Mono unbalanced input: 69.0k ohms
 Output noise, stereo mode, 8ohm load
 Low bias
 balanced outputs terminated with 600 ohms, Lch/Rch
 Wideband: 0.18mV / 0.11mV, 83.9dBW / 88.2dBW

A weighted: 0.072mV / 0.051mV, 91.9dBW / 94.9dBW
 unbalanced inputs terminated with 1k ohms, Lch/Rch
 Wideband: 0.30mV / 0.21mV, 79.5dBW / 82.6dBW
 A weighted: 0.10mV / 0.074mV, 89.0dBW / 91.6dBW
 balanced outputs terminated with 600 ohms, Lch/Rch
 High bias
 balanced outputs terminated with 600 ohms, Lch/Rch
 Wideband: 0.29mV / 0.12mV, 79.8dBW / 87.5dBW
 A weighted: 0.11mV / 0.056mV, 88.2dBW / 94.1dBW
 unbalanced inputs terminated with 1k ohms, Lch/Rch
 Wideband: 0.44mV / 0.27mV, 76.2dBW / 80.4dBW
 A weighted: 0.15mV / 0.087mV, 85.5dBW / 90.2 dBW
 balanced outputs terminated with 600 ohms, Lch/Rch
 Low bias
 Output noise, mono mode, 8ohm load
 Low bias
 balanced outputs terminated with 600 ohms
 Wideband: 0.19mV, 83.5dBW
 A weighted: 0.080mV, 91.0dBW
 unbalanced inputs terminated with 1k ohms
 Wideband: 0.53mV, 74.5 dBW
 A weighted: 0.18mV, 83.9 dBW
 balanced outputs terminated with 600 ohms
 High bias
 balanced outputs terminated with 600 ohms
 Wideband: 0.26mV, 80.7dBW
 A weighted: 0.097mV, 89.3dBW
 unbalanced inputs terminated with 1k ohms
 Wideband: 0.90mV, 69.9dBW
 A weighted: 0.29mV, 79.8dBW
 balanced outputs terminated with 600 ohms
 Low bias
Measurements summary
The Liberty Audio B2B100 is a mediumpower stereo power amplifier that can be switched between stereo and mono modes. Additionally, it has a switch for operating at low (Low) and high (Hi) biases.
Most of the measurements were affected by the choice of bias level; to avoid having to show all combinations, I concentrate here on the Hi bias setting and show, on the same or several charts, the effects of the two bias settings.
Chart 1 shows the B2B100’s frequency response with varying loads in stereo mode and with Low bias. With Hi bias, the curves are closer together simply because the output impedance is lower at the higher bias.
In mono mode, the shapes of the curves are similar, with greater separation between curves because the two stereo outputs are in series with the load, which raises the output impedance. In general, the output impedance of the amp, especially in the Low bias setting, would potentially cause the frequencyresponse variations with some speakers to be audible.
Chart 2 illustrates how the B2B100’s total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load for 8 and 4ohm loads. This is for the stereo mode and Hi bias. The amount of distortion and how it rises with output level is similar to some other MOSFET power amps I’ve measured recently, and suggests low amounts of overall loop feedback. The effects of the two bias settings are most visible in the mono mode, where the effective load on each half of the B2B100 is effectively halved. Chart 2A shows the four load conditions in Hi bias mode, Chart 2B in Low bias.
Chart 3 plots THD+N as a function of frequency at several different power levels. The shape of these curves is a bit unusual  the distortion is lower below 100Hz, rises in level to about 1kHz, then stays pretty constant up to 20kHz. It’s almost as if some internal openloop response shaping is taking place.
Damping factor vs. frequency is shown in Chart 4 for the two bias settings, the higher damping factor being for Hi bias.
A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal is plotted in Charts 5A and 5B for the two bias settings. With Hi bias, the higher signal harmonics disappear into the noise much more quickly. The magnitudes of the AC line harmonics are quite high, and largely a result of flux leakage from the power transformer.
Chart 1  Frequency response of output voltage as a function of output loading
Stereo and lowbias modes
Red line = open circuit
Magenta line = 8ohm load
Blue line = 4ohm load
Cyan line = NHT dummyspeaker load
Chart 2  Distortion as a function of power output and output loading
Stereo and highbias modes
(Line up at 100W to determine lines)
Top line = 8ohm SMPTE IM distortion
Second line = 4ohm SMPTE IM distortion
Third line = 8ohm THD+N
Bottom line = 4ohm THD+N
Chart 2A  Mono and highbias modes
(Line up at 100W to determine lines)
Top line = 8ohm SMPTE IM distortion
Second line = 4ohm SMPTE IM distortion
Third line = 8ohm THD+N
Bottom line = 4ohm THD+N
Chart 2B  Mono and lowbias modes
(Line up at 100W to determine lines)
Top line = 8ohm SMPTE IM distortion
Second line = 4ohm SMPTE IM distortion
Third line = 8ohm THD+N
Bottom line = 4ohm THD+N
Chart 3  Distortion as a function of power output and frequency
Mono and lowbias modes
(8ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 60W
Cyan line = 400W
Chart 4  Damping factor as a function of frequency
Stereo mode
Damping factor = output impedance divided into 8
Red line = low bias
Magenta line = high bias
Chart 5  Distortion and noise spectrum
Chart 5A  stereo and lowbias settings
1kHz signal at 10W into an 8ohm load
Chart 5B  stereo and highbias settings
1kHz signal at 10W into an 8ohm load