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
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.