Details

Parent Category: Products

Category: Amplifier Measurements

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.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on left channel through the balanced inputs unless otherwise noted.

Power output

• Output power at 1% THD+N: 198.4W @ 8 ohms, 285.5W @ 4 ohms
• Output power at 10% THD+N: 246.1W @ 8 ohms, 365.1W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 2.49A, 0.76PF, 233W
• AC-line current draw at standby: 0.28A, 0.64PF, 21.8W
• Gain: output voltage divided by input voltage, unbalanced and balanced inputs: 17.5X, 24.9dB 
• Input sensitivity for 1W output into 8 ohms, unbalanced and balanced inputs: 161.6mV
• Output impedance @ 50Hz: 0.153 ohm
• Input impedance @ 1kHz, unbalanced and balanced inputs: >800k ohms
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms, Lch/Rch
  •      Wideband: 0.58mV/0.58mV, -73.8 dBW/-73.8dBW
  •      A weighted: 0.085mV/0.085mV, -90.4dBW/-90.4dBW
• Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm, Lch/Rch
  •      Wideband: 0.58mV/0.58mV, -73.8 dBW/-73.8dBW
  •      A weighted: 0.085mV/0.084mV, -90.4dBW/-90.5dBW

Measurements summary

The Ayre Acoustics VX-5 is a medium-power stereo amplifier. Like previous Ayre power amplifiers, it is fully balanced and uses no overall negative feedback.

Chart 1 shows the VX-5’s frequency response with varying loads: very flat throughout the entire test range of 10Hz-200kHz. The output impedance is low, but still high enough that you can just see the effects of changes in load on the vertical scale used for FR charts. The response to a dummy NHT speaker load is barely discernible between the limits of an open circuit and a 4-ohm load, which indicates that the impedances of most speakers won’t materially affect the VX-5’s frequency-response output.

Chart 2 illustrates how total harmonic distortion plus noise (THD+N) vs. power varies with 1kHz and SMPTE intermodulation (IM) test signals and amplifier output load for 8- and 4-ohm loads. The amount of distortion and how it rises with output level is similar to some other MOSFET power amps I have measured recently.

THD+N as a function of frequency at different power levels is plotted in Chart 3. The amount of rise in distortion at high frequencies is reasonably low in this design.

Damping factor vs. frequency, shown in Chart 4, is of a quality rarely seen in power amplifiers: flat throughout the audioband! I can remember only a very few other designs that achieved this.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal is plotted in Chart 5. The magnitudes of the AC-line harmonics are very low and simple except for a few clustered around the suppressed 1kHz test signal. The dominant signal harmonic is the third, a testament to the circuitry’s basic symmetry.

Chart 1 - 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
Cyan line = NHT dummy load

Chart 2 - Distortion as a function of power output and output loading

(Line up at 10W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(4-ohm loading)
Red line = 2W
Magenta line = 20W
Blue line = 100W
Cyan line = 200W
Green line = 250W

Chart 4 - Damping factor as a function of frequency

Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

1kHz signal at 10W into an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

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 (stereo mode). Measurements were made on the left channel through balanced inputs unless otherwise noted.

Power output (stereo mode)

• Power output at 1% THD+N: 325.8W @ 8 ohms, 542.8W @ 4 ohms
• Power output at 10% THD+N: 400.7W @ 8 ohms, 671.2W @ 4 ohms

Power output (mono mode)

• Power output at 1% THD+N: 1100W @ 8 ohms, 1520W @ 4 ohms
• Power output at 10% THD+N: 1430W @ 8 ohms, 2220W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 0.77A, 0.6PF, 54W
• Gain: output voltage divided by input voltage, 8-ohm load
  •      Stereo mode: 35.9X, 31.1dB
  •      Mono mode: 71.9X, 37.1dB
• Input sensitivity for 1W output into 8 ohms
  •      Stereo mode: 78.8mV
  •      Mono mode: 39.3mV
• Output impedance @ 50Hz
  •      Stereo mode: 0.002 ohm
• Input impedance @ 1kHz
  
  •      Stereo mode, unbalanced inputs: 47k ohms
  •      Stereo mode, balanced inputs: 95k ohms
  •      Mono mode, balanced input: 47.5k ohms
• Output noise (stereo mode), 8-ohm load, unbalanced inputs terminated with 1k ohms, Lch/Rch
  
  •      Wideband: 0.148mV/0.155mV, -85.6dBW/-85.2dBW
  •      A weighted: 0.051mV/0.053mV, -94.9dBW/-94.5dBW
• Output noise (stereo mode), 8-ohm load, balanced inputs terminated with 600 ohms, Lch/Rch
  
  •      Wideband: 0.176mV/0.152mV, -84.1dBW/-85.4dBW
  •      A weighted: 0.050mV/0.050mV, -95.0dBW/-95.0dBW
• Output noise (mono mode), 8-ohm load, balanced inputs terminated with 600 ohms
  
  •      Wideband: 0.217mV, -82.3dBW
  •      A weighted: 0.070mV, -92.1dBW

Measurements summary

Simaudio’s Moon Evolution 870A is a new high-power stereo amplifier design that replaces the Moon Evolution W-8. As the 870A is also capable of operating in bridged mono, some essential measurements were made in that mode as well.

Chart 1 shows the 870A’s frequency response with varying loads. Because the amp’s damping factor and resultant very low output impedance cause no noticeable change with output loading, the curve shown is the same for an open circuit, for loads of 8 and 4 ohms, and for an NHT dummy speaker. The results were substantially the same for mono mode (not shown).

Chart 2A illustrates how total harmonic distortion plus noise (THD+N) vs. power varies with 1kHz and SMPTE intermodulation (IM) test signals and amplifier output for loads of 8 and 4 ohms. Chart 2B shows the results for mono mode. Here, the IM curves reveal some abrupt increases in distortion at higher powers, which sometimes indicates HF instability with lower-impedance loading.

Charts 3A and 3B show THD+N as a function of frequency at different power levels for, respectively, the stereo and mono modes. The amount of rise in distortion at high frequencies is admirably low.

Damping factor vs. frequency is shown in Chart 4. This is extremely high, exceeding 500 at 20kHz. The damping factor in mono mode (not shown) was similar in shape but about half the magnitude.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal is plotted in Chart 5. The magnitudes of the AC-line harmonics are relatively low; the signal harmonics are predominantly the second and third. The spectrum for the mono mode (not shown) is similar regarding the signal harmonics, but the AC-line harmonics have largely canceled, due to the differential subtraction action of similar signals.

Chart 1 - Frequency response of output voltage as a function of output loading

Stereo mode
Red line = open circuit, 8-ohm load, 4-ohm load

Chart 2 - Distortion as a function of power output and output loading

Chart 2A

Stereo mode
(Line up at 100W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 2B

Mono mode
(Line up at 100W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Fourth line = 4-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

Chart 3A

Stereo mode
(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 30W
Cyan line = 100W
Green line = 250W

Chart 3B

Mono mode
(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 30W
Cyan line = 100W
Green line = 300W
Yellow line = 900W

Chart 4 - Damping factor as a function of frequency

Stereo mode
Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

Stereo mode
1kHz signal at 10W into a 4-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

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.
• AC-line current draw at high bias: 1.63A, 0.71PF, 138W
• AC-line current draw at low bias:  0.92A,  0.72PF, 81W
• Gain: output voltage divided by input voltage, 8-ohm 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
• 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
• Output impedance @ 50Hz
  •      Stereo low-bias mode: 0.279 ohm
  •      Stereo high-bias mode: 0.180 ohm
  •      Mono low-bias mode: 0.571 ohm
  •      Mono high-bias 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, 8-ohm 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
  • 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
• Output noise, mono mode, 8-ohm 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
  • 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

Measurements summary

The Liberty Audio B2B-100 is a medium-power 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 B2B-100’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 frequency-response variations with some speakers to be audible.

Chart 2 illustrates how the B2B-100’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 4-ohm 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 B2B-100 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 open-loop 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 low-bias modes

Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy-speaker load

Chart 2 - Distortion as a function of power output and output loading

Stereo and high-bias modes

(Line up at 100W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 2A - Mono and high-bias modes

(Line up at 100W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 2B - Mono and low-bias modes

(Line up at 100W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

Mono and low-bias modes

(8-ohm 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 low-bias settings

1kHz signal at 10W into an 8-ohm load

Chart 5B - stereo and high-bias settings

1kHz signal at 10W into an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

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 (stereo mode). Measurements were made on the left channel unless otherwise noted. The Audio Precision AUX-0025 measurement filter was used unless otherwise noted.

Power output (stereo mode)

• Power output at 1% THD+N: 63.6W @ 8 ohms, 106.7W @ 4 ohms
• Power output at 10% THD+N: 84.7W @ 8 ohms, 137.8W @ 4 ohms

Power output (mono mode)

• Power output at 1% THD+N: 231.3W @ 8 ohms, 366.7W @ 4 ohms
• Power output at 10% THD+N: 289.0W @ 8 ohms, 476.0W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 0.17A, 0.42PF, 8.6W
• Gain: output voltage divided by input voltage, 8-ohm load
  •      Stereo mode: 17.2X, 24.7dB
  •      Mono mode: 34.7X, 30.8dB
• Input sensitivity for 1W output into 8 ohms
  •      Stereo mode: 164.4mV
  •      Mono mode: 81.5mV
• Output impedance @ 50Hz
  •      Stereo mode: 0.012 ohm
  •      Mono mode: 0.027 ohm
• Input impedance @ 1kHz
  
  •      Stereo mode, Lch/Rch: 8.2k ohms, 46.3k ohms
  •      Biwire mode, Lch/Rch: 8.2k ohms, 8.2k ohms
  •      Mono mode: 8.2k ohms
• Output noise (stereo mode), 8-ohm load, unbalanced inputs terminated with 1k ohms, Lch/Rch
  
  •      Wideband (no AUX-0025 filter): 1.08V/0.88V, -8.9dBW/-10.1dBW
  •      Wideband: 1.54mV/1.40mV, -65.3dBW/-66.1dBW
  •      A weighted: 0.058mV/0.072mV, -93.8dBW/-99.1dBW
• Output noise (mono mode), 8-ohm load, unbalanced inputs terminated with 1k ohms
  
  •      Wideband (no AUX-0025 filter): 1.76V, -4.1dBW
  •      Wideband: 1.72mV, -64.3dBW
  •      A weighted: 0.086mV, -90.3dBW

Measurements summary

The Calyx Femti is a stereo power amplifier of moderate output that uses a bridgeable ICEpower 125ASX2 switching amp preceded by a custom input buffer and input-switching circuit board. The switching amp is the lowest-powered of the three available ICEpower models.

Because the Femti can be switched from stereo to bridged-mono mode, measurements were taken in both modes. In the accompanying charts, the suffix “A” denotes a measurement of bridged mode. In the third mode, biwiring, in which the two stereo channels are both fed the same input signal, is no different from the performance in stereo mode, except for a peculiarity of the input impedance (see data above).

Charts 1 and 1A show the frequency response of the Femti with varying loads. The amount of switching carrier noise in bridged mode prevented getting a good measurable response without the Audio Precision AUX-0025’s external filter, so to get compatible responses in the stereo and bridged modes, the filter was used in both cases. There is a bit more noticeable deviation of high-frequency response in bridged mode, with an earlier high-frequency rolloff and a bit more out-of-band high-frequency peaking.

Charts 2 and 2A illustrate how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE intermodulation test signals and amplifier output load for 8- and 4-ohm loads.

THD+N as a function of frequency at several different power levels is plotted in Charts 3 and 3A. High-frequency distortion rise with increasing frequency is considerable, and there is also a rise in low-frequency distortion with power. As can be seen, the apparent noise floor is somewhat lower in bridged mode, as the amount of distortion is lower in the midband.

The Femti’s damping factor vs. frequency, shown in Chart 4, is of a value and nature typical of many solid-state amplifiers: high up to about 1-2kHz, then rolling off with rising frequency.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal in stereo mode is plotted in Chart 5. The magnitudes of the AC-line harmonics are reasonably low, and the signal harmonics are low in amplitude. The 10W/4-ohm spectrum for the bridged mode (not shown) looked about the same as in Chart 5.

Chart 1 - Frequency response of output voltage as a function of output loading

Stereo mode
Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy-speaker load

Chart 1A

Mono mode
Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy-speaker load

Chart 2 - Distortion as a function of power output and output loading

Stereo mode
(Line up at 20W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 2A

Mono mode
(Line up at 10W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Second line = 4-ohm THD+N
Third line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

Stereo mode
(4-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 20W
Cyan line = 70W
Green line = 100W

Chart 3A

Mono mode
(4-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 50W
Cyan line = 200W
Green line = 400W

Chart 4 - Damping factor as a function of frequency

Stereo mode
Damping factor = output impedance divided into 8

Chart 4A

Mono mode
Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

Stereo mode
1kHz signal at 10W into an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

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.

Note: Measurements were made at 120V AC line voltage and through the balanced input and with the 0dB gain switch position unless otherwise noted. All measurements made with Audio Precision AUX-0025 filter (AP filter) except where noted.

Power output with 120VAC

• Output power at 1% THD+N: 1130W @ 8 ohms, 2120W @ 4 ohms
• Output power at 10% THD+N: 1430W @ 8 ohms, 2210W @ 4 ohms

Power output with 240VAC

• Output power at 1% THD+N: 1130W @ 8 ohms, 2160W @ 4 ohms
• Output power at 10% THD+N: 1430W @ 8 ohms, 2850W @ 4 ohms

Additional data

• This amplifier does not invert polarity (XLR or RCA input).
• AC-line current draw at idle: 0.36A, 0.69PF, 29.8W
• Gain: output voltage divided by input voltage, 8-ohm load
  
  •      Unbalanced inputs: 28.5X, 29.1dB
  •      Balanced inputs: 27.7X, 28.4dB
• Input sensitivity for 1W output into 8 ohms
  •      Unbalanced inputs: 91.0mV
  •      Balanced inputs: 102.0mV
• Output impedance @ 50Hz: 0.0079 ohm
• Input impedance @ 1kHz
  •      Unbalanced inputs: 8.9k ohms
  •      Balanced inputs: 12.0k ohms
Output noise, 8-ohm load, unbalanced or balanced inputs (termination 1k ohm for unbalanced, 600 ohms for balanced)
•      Without Audio Precision AUX-0025 filter, wideband: 1.025V, -9.92dBW
•      With Audio Precision AUX-0025 filter, wideband: 1.93mv, -63.3dBW
•      With Audio Precision AUX-0025 filter, A weighted: 0.128mV, -83.4dBW

Measurements summary

The Anthem Statement M1 is a high-powered, solid-state, mono power amplifier designed in-house by Anthem.

Chart 1 shows the M1’s frequency response with varying loads. As can be seen, the high-frequency response is little affected by load. Without the Audio Precision filter, the -3dB point rose from about 38 to 48kHz. The output impedance is so low that the response with the NHT dummy speaker load didn’t show up at the chart resolution used.

Chart 2 illustrates how the M1’s total harmonic distortion plus noise (THD+N) vs. power varied for 1kHz and SMPTE IM test signals and amplifier output load for 8- and 4-ohm loads. These data were taken with the normal 120V AC input. Since the M1 can also accept 240V, I also checked its THD+N vs. power output at that voltage. This is plotted in Chart 2A, along with a curve for 2-ohm loading. The 8-ohm power into clipping was unchanged, while the 4-ohm power was increased a bit. The M1’s power output into 2 ohms reached nearly 3kW before the amp’s 10A circuit breaker popped. With that load, there’s no question that it would have popped earlier if fed 120V. Still, 3kW without clipping is prodigious output!

THD+N as a function of frequency at several different power levels is plotted in Chart 3. The rise in distortion with increasing frequency is quite pronounced at all power levels, the amount above 10kHz being reduced by the AP filter.

The M1’s damping factor vs. frequency, shown in Chart 4, is typical of most solid-state analog power amplifiers: high at low frequencies, and, in this case, beginning to decrease above about 200Hz.

A spectrum of the M1’s harmonic distortion and noise when fed a 10W, 1kHz test signal is plotted in Chart 5. The magnitudes of the AC line harmonics are very low here, and the signal harmonics are predominantly second and third, with a number of higher harmonics at lower amplitudes.

Chart 1 - 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 (120VAC)

(Line up at 10W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 2A - Distortion as a function of power output and output loading (240VAC)

(Line up at 10W to determine lines)
Top line = 2-ohm THD+N
Second line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(8-ohm loading)
Red line = 10W
Magenta line = 30W
Blue line = 200W
Cyan line = 500W
Green line = 900W

Chart 4 - Damping factor as a function of frequency

Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

1kHz signal at 10W into an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

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 (stereo mode). Measurements were made on the left channel through the balanced input unless otherwise noted. The Audio Precision AUX-0025 measurement filter was used unless otherwise noted.

Power output (stereo mode)

• Power output at 1% THD+N: 133.7W @ 8 ohms, 212.2W @ 4 ohms
• Power output at 10% THD+N: 165.0W @ 8 ohms, 267.7W @ 4 ohms

Power output (mono mode)

• Power output at 1% THD+N: 477.7W @ 8 ohms, 687.9W @ 4 ohms
• Power output at 10% THD+N: 610.0W @ 8 ohms, 900.0W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 0.29A, 0.52PF, 17.7W
• Gain (stereo mode): output voltage divided by input voltage, 8-ohm load
  •      Unbalanced inputs: 26.5X, 28.5dB
  •      Balanced inputs: 13.1X, 22.4dB
• Gain (mono mode): output voltage divided by input voltage, 8-ohm load
  •      Unbalanced inputs: 52.6X, 34.4dB
  •      Balanced inputs: 26.2X, 28.4dB
• Input sensitivity (stereo mode) for 1W output into 8 ohms
  •      Unbalanced inputs: 107.0mV
  •      Balanced inputs: 216.0mV
• Input sensitivity (mono mode) for 1W output into 8 ohms
  •      Unbalanced inputs: 54.0mV
  •      Balanced inputs: 108.0mV
• Output impedance @ 50Hz
  •      Stereo mode: 0.026 ohm
  •      Mono mode: 0.032 ohm
• Input impedance @ 1kHz (stereo and mono modes)
  
  •      Unbalanced and balanced inputs: >700k ohms
• Output noise (stereo mode), 8-ohm load, unbalanced inputs terminated with 1k ohms, Lch/Rch
  
  •      Wideband (no AUX-0025 filter): 1.08V/1.10V, -8.4dBW/-8.2dBW
  •      Wideband: 1.5mV/1.25mV, -65.5BW/-67.1dBW
  •      A weighted: 0.22mV/0.23mV, -82.2dBW/-83.0dBW
• Output noise (stereo mode), 8-ohm load, balanced inputs terminated with 600 ohms, Lch/Rch
  
  •      Wideband (no AUX-0025 filter): 1.08V/1.09V, -8.4dBW/-8.3dBW
  •      Wideband: 1.48mV/1.23mV, -65.6dBW/-67.2dBW
  •      A weighted: 0.22mV/0.22mV, -82.2dBW/-82.2dBW
• Output noise (mono mode), 8-ohm load, unbalanced inputs terminated with 1k ohms
  
  •      Wideband (no AUX-0025 filter): 1.56V, -5.2dBW
  •      Wideband: 1.68mV, -64.5dBW
  •      A weighted: 0.14mV, -86.1dBW
• Output noise (mono mode), 8-ohm load, balanced inputs terminated with 600 ohms
  
  •      Wideband (no AUX-0025 filter): 1.76V, -4.1dBW
  •      Wideband: 1.72mV, -64.3dBW
  •      A weighted: 0.11mV, -88.2dBW

Measurements summary

The Eximus S1 is a moderately powerful amplifier that uses a custom input buffer and input-switching circuit board, followed by a bridgeable ICEpower 250ASX2 switching amplifier.

Because the S1 can be switched between stereo and bridged-mono operation, measurements were taken of its performance in both modes. In each of the charts of the measurements, the suffix “A” indicates the mono-mode measurements.

Charts 1 and 1A show the frequency response of the S1 with varying loads. The amount of switching carrier noise in mono mode prevented getting a good measurable response without the Audio Precision AUX-0025 external filter, so the filter was used in both cases to provide comparable responses for stereo and mono operation. There is a bit more noticeable deviation of high-frequency response in mono mode, but of more interest is the rise in the low-frequency response. Apparently, the designers felt this would give more weight to the S1’s low-end sound.

Charts 2 and 2A illustrate how the S1’s total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE intermodulation (IM) test signals and amplifier output load for 8- and 4-ohm loads. Testing into a 4-ohm load in mono mode caused the AC line fuse to blow. I was able to get a reading of THD+N once before the fuse blew, but couldn’t measure the SMPTE IM distortion because this test takes longer to run; the fuse blew before the test could be completed.

THD+N as a function of frequency at several different power levels is plotted in Charts 3 and 3A. High-frequency distortion rises considerably with increasing frequency; to keep the S1 from shutting down, the high-frequency limit was lowered to 6kHz at higher power levels.

The S1’s damping factor vs. frequency, shown in Charts 4 and 4A, is of a value and nature typical of many solid-state amplifiers: high up to about 1-2kHz, then rolling off with frequency.

A spectrum of the S1’s harmonic distortion and noise residue of a 10W, 1kHz test signal is plotted in Charts 5 and 5A. The magnitude of the AC-line harmonics is relatively low, with some 60Hz showing in stereo mode but not in mono mode, the latter probably due to cancellation. The signal harmonics are low in amplitude and noticeably simpler, with a cleaner baseline, in mono mode.

Chart 1 - Frequency response of output voltage as a function of output loading

Stereo mode
Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load

Chart 1A

Mono mode
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

Stereo mode
(Line up at 10W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 2A

Mono mode
(Line up at 10W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm THD+N
Third line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

Stereo mode
(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 60W
Cyan line = 100W

Chart 3A

Mono mode
(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 100W
Cyan line = 300W
Green line = 400W

Chart 4 - Damping factor as a function of frequency

Stereo mode
Damping factor = output impedance divided into 8

Chart 4A

Mono mode
Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

Stereo mode
1kHz signal at 10W into an 8-ohm load

Mono mode
1kHz signal at 10W into an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

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.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on left channel through the balanced inputs and 8-ohm outputs unless otherwise noted.

Power output

• Output power at 1% THD+N: 26.0W @ 8 ohms, 15.0W @ 4 ohms
• Output power at 10% THD+N: 40.0W @ 8 ohms, 32.0W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 1.42A, 0.89PF, 151W
• Gain: output voltage divided by input voltage, volume at maximum, Lch/Rch: 18.61X, 25.4dB:
  •      Balanced inputs: 39.75X, 32.0dB / 40.31X, 32.1dB
  •      Unbalanced inputs: 50.32X, 34.0dB / 52.18X, 34.4dB
• Input sensitivity for 1W output into 8 ohms, volume at maximum, Lch/Rch:
  •      Balanced inputs: 0.071mV / 0.70mV
  •      Unbalanced inputs: 0.56mV / 0.54mV
• Output impedance @ 50Hz: 2.15 ohms
• Input impedance @ 1kHz: 50k ohms
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms, Lch/Rch
  •      Volume control at reference position
              Wideband: 0.89 mV, -70.0dBW / 4.88mV, -55.3dBW
              A weighted: 0.21 mV, -82.6dBW / 0.70 mV, -72.1dBW
  •      Volume control full clockwise
              Wideband: 1.11mV, -68.2dBW / 5.08mV, -54.9dBW
              A weighted: 0.28mV, -80.1dBW / 0.71mV, -72.0dBW
  •      Volume control full counterclockwise
              Wideband: 0.89mV, -70.0dBW / 4.89 mV, -55.2 dBW
              A weighted: 0.18mV, -83.9dBW / 0.68 mV, -72.4 dBW
• Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm, Lch/Rch
  •      Volume control at reference position
              Wideband: 1.12mV, -68.1dBW / 5.09mV, -54.9dBW
              A weighted: 0.20mV, -83.0dBW / 0.74mV, -71.6dBW
  •      Volume control full clockwise
              Wideband: 1.59mV, -65.0dBW / 4.97mV, -55.1dBW
              A weighted: 0.25mV, -81.1dBW / 0.73mV, -71.8dBW
  •      Volume control full counterclockwise
              Wideband: 0.95mV, -69.5dBW / 5.32mV, -54.5dBW
              A weighted: 0.19 mV, -83.5 dBW / 0.72 mV, -71.9 dBW

Measurements summary

The JE Audio VS70.1 is a medium-power tubed power amplifier with a front-panel volume control. Its overall gain is 6-7dB over the "nominal" power gain of 26dB. However, the extra gain would be useful for low-output CDs, such as Reference Recordings’ HRx discs.

Chart 1 shows the VS70.1’s frequency response with varying loads. This was made at the usual 1W/8-ohm level, with the volume control turned fully clockwise. The frequency-response variation with the NHT dummy load is of the order of ±1.5dB. The high-frequency rolloff is nicely controlled in that its shape is quite independent of load.

With the reference condition set up for measuring integrated amplifiers -- i.e., volume control set for 5W output into 8 ohms for 500mV input -- another response was run, and is shown in Chart 1A. Here we see that the HF response is a little more extended, and the very low-frequency level is starting to roll off because of output-transformer limitations. Channel tracking as a function of volume-control position down from this reference condition was generally within ±1dB down to 50dB of attenuation, below which hum, noise, and capacitive coupling altered the response and the channel separation.

Chart 2 illustrates how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load. It is apparent that the power is maximized for the 8-ohm load, whereas the power for a 4-ohm load is lower at higher distortion. Further, the amounts of intermodulation distortion are rather excessive at the higher power levels.

Chart 3 plots THD+N as a function of frequency for 8-ohm loading at several different power levels. The rise in distortion at higher frequencies is reasonably low. Because of output-transformer characteristics, low-frequency distortion gets progressively worse as the bass frequency rises and the power level increases.

The VS70.1’s damping factor vs. frequency (Chart 4) is fairly low, but not unusually so for a tubed power amplifier. What is good is that it is quite flat with frequency.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal into 8 ohms is plotted in Chart 5. The magnitudes of the AC-line harmonics are quite high and complex, as are the signal harmonics. Intermodulation components of line harmonics with signal harmonics are numerous, and can be seen at the baseline of the signal harmonics.

Chart 1 - Frequency response of output voltage as a function of output loading

(Volume control fully clockwise)
Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy load

Chart 1A (Additional Measurement) - Frequency response with volume control at reference position (8-ohm load)

Red line = left channel
Blue line = right channel

Chart 2 - Distortion as a function of power output and output loading

(Line up at 20W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(8-ohm loading)
Red line = 1W
Magenta line = 5W
Blue line = 15W
Cyan line = 30W
Green line = 35W

Chart 4 - Damping factor as a function of frequency

Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

1kHz signal at 10W into an 8-ohm load

Details

Parent Category: Products

Category: Amplifier Measurements

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.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on left channel through the balanced inputs unless otherwise noted.

Power output

• Output power at 1% THD+N: 224.8W @ 8 ohms, 372.2W @ 4 ohms
• Output power at 10% THD+N (est., see text): 250W @ 8 ohms, 400W @ 4 ohms

Additional data

• This amplifier does not invert polarity.
• AC-line current draw at idle: 1.52A, 0.75PF, 137W
• AC-line current draw at standby: 0.4A, 0.77PF, 37W
• Gain: output voltage divided by input voltage for balanced inputs: 18.61X, 25.4dB 
• Input sensitivity for 1W output into 8 ohms, balanced inputs: 152.0mV
• Output impedance @ 50Hz: 0.15 ohm
• Input impedance @ 1kHz: 1M ohm
• Output noise, 8-ohm load, balanced inputs, termination 600 ohms, Lch/Rch
  •      Wideband: 0.369mV/0.363mV, -77.7 dBW/-77.8dBW
  •      A weighted: 0.078mV/0.076mV, -91.2dBW/-91.4dBW

Measurements summary

The VX-R, one of Ayre Acoustics’ newest models, is a medium-power solid-state stereo power amplifier. Though of relatively small size, this dual-mono design, milled from a solid block of aluminum, is one heavy beast of an amp: It weighs almost 80 pounds.

Chart 1 shows the VX-R’s frequency response with varying loads. The high-frequency response is quite wide, with an approximate 3dB down point in excess of 200kHz.

The frequency response varies a small amount with load; therefore, the VX-R’s output impedance is reasonably low. The effect of the NHT dummy load is hard to see at the resolution at which this chart is usually shown; it amounts to a frequency-response deviation of about ±0.2dB.

Chart 2A illustrates how the VX-R’s total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output for 8- and 4-ohm loads. The protection fuses in the “front end” of the VX-R blew repeatedly when I attempted to drive it to 10% THD+N, so the values listed in the Additional Data are estimates. The amount of distortion is reasonable for what is claimed to be a no-overall-feedback design.

Chart 3 plots the THD+N as a function of frequency at several different power levels. The amount of increase in distortion at high frequencies is admirably low up to 150W. Attempts to get data at the 200W level blew the front-end fuses.

The VX-R’s plot of damping factor vs. frequency (Chart 4) is unusually flat. I have seen only a few amps with this characteristic. This usually goes along with flat distortion amount with changing frequency, as is the case with this design.

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal is plotted in Chart 5. The magnitudes of the AC-line harmonics are very low, and the signal harmonics are predominantly the second and third; all higher harmonics are an order of magnitude lower.

Chart 1 - 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
Cyan line = NHT dummy load

Chart 2 - Distortion as a function of power output and output loading

(Line up at 10W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 70W
Cyan line = 150W

Chart 4 - Damping factor as a function of frequency

Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

1kHz signal at 10W into an 8-ohm load