August 2006

Bel Canto Design e.One REF1000 Mono 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 one channel driven (this is a mono amplifier) using the balanced inputs and an Audio Precision AUX-0025 measurement filter unless otherwise noted.
• This amplifier does not invert polarity.
• AC line current draw at idle: 0.26A.
• Input impedance @ 1kHz
  • Balanced input: 8.7k ohms.
  • Unbalanced input: 11.0k ohms.
• Output impedance at 50Hz: 0.008 ohms.
• Gain (8-ohm load): 23.3X, 27.4dB.
• Output noise, 8-ohm load, balanced input, 600-ohm input termination: wideband without A/P AUX-0025 filter 1.29V, -6.8 dBW; wideband 2.07mV, -62.7 dBW; A weighted 0.091 mV, -89.8 dBW.

Power output with 1kHz test signal

• 8-ohm load at 1% THD: 597W
• 8-ohm load at 10% THD: 500W
  
  
• 4-ohm load at 1% THD: 1172W
• 4-ohm load at 10% THD: 1152W

General

The Bel Canto e.One REF1000 is a high-power switching design utilizing the ICEpower 1000ASP module. This marks a departure for Bel Canto, as I believe that their earlier amplifier designs used Tripath circuitry -- quite different from the ICEpower approach.

Chart 1 shows the frequency response of the amp with varying loads. As can be seen, the output impedance, as judged by the closeness of spacing between the curves of open-circuit, 8-ohm, and 4-ohm loading, is quite low up to about 2-3kHz. Above this, the output impedance has increased to where one can see some variation with load. Above 3kHz, the variation with the NHT dummy speaker load is of the order of perhaps +/-0.4dB. As switching amps go, the ICEpower modules have pretty good high-frequency response control above the audio range with varying loads.

Chart 2 illustrates how total harmonic distortion plus noise vs. power varies for 1kHz and SMPTE IM test signals with 4- and 8-ohm loads. As can be seen, attainable power is greater for the 4-ohm load, as is usual for most power amplifiers. Amount of distortion in Chart 2 is quite reasonable.

Total harmonic distortion plus noise as a function of frequency at several different power levels is plotted in Chart 3. This amplifier does exhibit quite a bit of rise in high-frequency distortion starting below 1kHz. At the higher power levels, it starts to lose it above 10kHz. There is also some rise in distortion at low frequencies.

Damping factor vs. frequency is shown in Chart 4 and is very high at low frequencies but declines precipitously around a few hundred Hz -- not unusual behavior for amplifiers with very high damping factors at low frequencies.

A spectrum of the harmonic distortion and noise residue of a 10W 1kHz test signal is plotted in Chart 5. The amount of AC-line harmonics is admirably low. The signal frequency harmonics are dominantly of odd order.

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

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

4-ohm output loading
Green: 900W
Cyan line: 500W
Blue line: 100W
Magenta line: 10W
Red line: 1W

Damping factor = output impedance divided into 8

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

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