July 2004

Simaudio Moon W-6 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, 8-ohm load, unbalanced input, 1k-ohm input termination: wideband 0.309mV, -79.2dBW; A weighted 0.084mV, -90.4dBW.
• Output noise, 8-ohm load, balanced input, 600-ohm 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

• 8-ohm load at 1% THD: 440W
  
  
• 4-ohm load at 1% THD: 770W

General

The Moon W-6 is a high-power solid-state 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, 8-ohm, and 4-ohm 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 4-ohm 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 solid-state 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 AC-line harmonics are quite low for this amplifier. The test-signal harmonics are dominantly odd harmonic with a slow falloff of magnitude with harmonic order.

Red line: open circuit
Magenta line: 8-ohm load
Blue line: 4-ohm 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

8-ohm output loading
Green lin: 400W
Cyan line: 200W
Blue line: 70W
Magenta line: 10W
Red line: 1W

Damping factor = output impedance divided into 8

1kHz signal at 10W into an 8-ohm load

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