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
AUX0025 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 (8ohm load): 23.3X, 27.4dB.
 Output noise, 8ohm load, balanced input, 600ohm input
termination: wideband without A/P AUX0025 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
 8ohm load at 1% THD: 597W
 8ohm load at 10% THD: 500W
 4ohm load at 1% THD: 1172W
 4ohm load at 10% THD: 1152W
General
The Bel Canto e.One REF1000 is a highpower 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 opencircuit, 8ohm, and 4ohm loading, is quite low up to about
23kHz. 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
highfrequency 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 8ohm loads. As can
be seen, attainable power is greater for the 4ohm 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 highfrequency 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 ACline harmonics is admirably
low. The signal frequency harmonics are dominantly of odd order.
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
Cyan line: NHT dummyspeaker load
Chart 2  Distortion as a Function
of Power Output and Output Loading 
(line up at 10W to determine lines)
Top line: 4ohm SMPTE IM
Second line: 8ohm SMPTE IM
Third line: 4ohm THD+N
Bottom line: 8ohm THD+N
Chart 3  Distortion
as a Function of Power Output and Frequency 
4ohm output loading
Green: 900W
Cyan line: 500W
Blue line: 100W
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 
1kHz signal at 10W into a 4ohm load
