March 2008
Oracle Audio SI
1000 Integrated 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 both
channels driven; measurements made on left channel with unbalanced input unless otherwise
noted.
 This integrated amplifier does not invert polarity.
 AC line current draw:
 at idle: 0.72A
 in standby: 0.32A
 Input sensitivity for 1W output into 8 ohms, volume at
maximum: 49.2mV
 Input impedance @ 1kHz:
 balanced inputs: 47.0k ohms
 unbalanced inputs: 24.0k ohms
 Output impedance at 50Hz: 0.4 ohms
 Gain, output voltage divided by input voltage, volume at
maximum: 57.2X, 35.2dB
 Output noise, 8ohm load, 1kohm input termination, Lch/Rch
 Volume control at reference position
 wideband: 0.65mV, 72.8dBW / 0.68mV, 72.4dBW
 A weighted: 0.28mV, 80.1dBW / 0.35mV, 78.2dBW
 Volume control full clockwise
 wideband: 1.39mV, 66.2dBW / 1.37mV, 66.3dBW
 A weighted: 0.59mV, 73.6dBW / 0.62mV, 73.2dBW
 Volume control full counterclockwise
 wideband: 0.60mV, 73.5dBW / 0.66mV, 72.6dBW
 A weighted: 0.27mV, 80.4dBW / 0.34mV, 78.4dBW
Power output with 1kHz test signal
 8ohm load at 1% THD: 141.3W
 8ohm load at 10% THD: 173.1W
 4ohm load at 1% THD: 213.4W
 4ohm load at 10% THD: 266.6W
General
The Oracle SI 1000 is a remotecontrolled, mediumpower
solidstate integrated amplifier. Overall gain of this unit is about right for a modern
integrated amplifier  a bit higher than average poweramponly gain.
Chart 1 shows the frequency response of the amp with
varying loads. This plot was made with the reference volumecontrol position as set for
0.5V input to produce 5W output into an 8ohm load. The highfrequency response is
moderately wide, with an approximate 3dBdown point of about 60kHz. Output impedance as
judged by the closeness of spacing between the curves of opencircuit, 8ohm and 4ohm
loading is somewhat high for solidstate power amplifiers. Still, the variation with the
NHT dummy speaker load is only of the order of +/ 0.25dB  it’s not going to make
much of an audible difference with most speakers. Of note, the highfrequency rolloff
shape is nicely independent of loading. The frequency response of this unit was quite
independent of volumecontrol setting. Tracking between channels was within about 0.1dB
from full up to 70dB of attenuation.
Chart 2 illustrates how total harmonic distortion plus
noise vs. power varies for 1kHz and SMPTE IM test signals and amplifier output load. Not
typical of most solidstate amplifiers, distortion maximizes right in the typical
listening range of power output, in the 15W range.
Total harmonic distortion plus noise as a function of
frequency at several different power levels is plotted in Chart 3 for 4ohm loading. The
amount of rise in distortion at high frequencies is quite pronounced, with some rise at
the very low frequencies at 200W output.
Damping factor vs. frequency is shown in Chart 4 and is of
a value and nature not typical of most power amplifiers  being relatively low and
uniform over most of the audio range. As mentioned earlier, the output impedance is
relatively high for a solidstate power amplifier, yielding a damping factor of about 20.
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 ACline
harmonics are moderately high and complex in nature. However, intermodulation components
of line harmonics with signal harmonics are low. Signal harmonics consist of a tapering
off spectrum of even and odd harmonics.
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 line: 200W
Cyan line: 160W
Blue line: 120W
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 an 8ohm load
