February 2004

Flying Mole Corporation DAD-M100pro HT 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.
• Power output and distortion plotted with one channel driven (this is a mono amplifier).
• Gain: 25.6x, 28.2dB.
• Output noise, 8-ohm load, 1k-ohm input termination: wideband 205mV, -22.8dBW; A weighted 0.26mV, -80.7dBW.
• AC line current draw at idle: 160mA.
• Output impedance at 50Hz: 0.08 ohms.
• This amplifier does not invert polarity.

Power output with 1kHz test signal

• 8-ohm load at 1% THD: 103W
  
  
• 4-ohm load at 1% THD: 153W

General

The Flying Mole DAD-M100pro HT is an interesting switching-amp design utilizing an AC line-level switching power supply. This eliminates the usual 60Hz power transformer and, hence, accounts for its light weight.

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 very low up to several kilohertz, beyond which the effect of the output low-pass filter comes into play. The effect of this would be that the last two octaves of the audio range might have as much variation with a real speaker load of up to +/-1dB depending on the particular speaker’s impedance characteristic. The variation with the NHT dummy speaker load is about +/- 0.5dB over the audio range. The literature for this amp design suggests that there is some "virtual damping" in the output low-pass filter, but the chart suggests otherwise. 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 relatively low -- a desirable characteristic. Damping factor versus frequency is shown in Chart 4. A spectrum of the harmonic distortion and noise residue is plotted in Chart 5. The overall noise floor of this plot is somewhat higher than most linear solid-state amplifiers due to the effect of the switching noise in the output.

Red line: open circuit
Cyan line: NHT dummy-speaker load
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

4-ohm output loading
Cyan line: 160W
Red line: 70W
Magenta line: 20W
Blue line: 2W

Damping factor = output impedance divided into 8

1kHz signal at 10W into a 4-ohm load

• Go Back