July 2004
Simaudio Moon
W6 Mono Amplifiers: 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 with 120V AC line voltage.
 Gain: 71.2x, 37dB.
 Output noise, 8ohm load, unbalanced input, 1kohm input
termination: wideband 0.309mV, 79.2dBW; A weighted 0.084mV, 90.4dBW.
 Output noise, 8ohm load, balanced input, 600ohm input
termination: wideband 0.288mV, 79.8dBW; A weighted 0.087mV, 90.2dBW.
 AC line current draw at idle: 0.46A.
 Output impedance at 50Hz: 0.0014 ohms.
 This amplifier does not invert polarity.
Power output with 1kHz test signal
 8ohm load at 1% THD: 440W
 4ohm load at 1% THD: 770W
General
The Moon W6 is a highpower solidstate design with
typically wide bandwidth and very low output impedance.
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, 8ohm, and 4ohm loading, is quite low. The variation
with the NHT dummy load would be absolutely negligible. Chart 2 illustrates how total
harmonic distortion plus noise versus power varies for 1kHz and SMPTE IM test signals and
amplifier output load. As can be seen, attainable power is greater for the 4ohm load as
is usual for most power amplifiers. Total harmonic distortion plus noise as a function of
frequency at several different power levels is plotted in Chart 3. Amount of rise in
distortion at high frequencies is typical of most modern solidstate power amplifiers.
Note how the amount of distortion here is fairly constant with power level over much of
the frequency range. Damping factor versus frequency is shown in Chart 4. Unusual is how
high the damping factor is at low frequencies. A spectrum of the harmonic distortion and
noise residue is plotted in Chart 5. The ACline harmonics are quite low for this
amplifier. The testsignal harmonics are dominantly odd harmonic with a slow falloff of
magnitude with harmonic 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
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 
8ohm output loading
Green lin: 400W
Cyan line: 200W
Blue line: 70W
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
