December 2003

Monarchy Audio SE-160 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: 11.3x, 21.1dB.
• Output noise, 8-ohm load, unbalanced input, 1k-ohm input termination: wideband 0.536mV, -74.5dBW; A weighted 0.185mV, -83.7dBW.
• AC line current draw at idle: 1.47A.
• Output impedance at 50Hz: 0.3 ohms.
• This amplifier inverts polarity.

Power output with 1kHz test signal

• 8-ohm load at 1% THD: 40W
• 8-ohm load at 10% THD: 230W
  
  
• 4-ohm load at 1% THD: 72W
• 4-ohm load at 10% THD: 470W

General

The Monarchy Audio SE-160 is an interesting attempt to duplicate some of the characteristics of a single-ended (SE) tube amplifier in a hybrid solid-state design. What is very SE-tube-like is the amount and way the distortion rises with power output, with the second harmonic being dominant. This distortion characteristic, no doubt, is generated in the vacuum-tube front end of this design. What is different from most tube SE amplifiers is the wide bandwidth and low out impedance of the SE-160.

Chart 1 shows the frequency response of the amp with varying loads. As can be seen in the chart, the high-frequency bandwidth is about 100kHz and is nicely controlled in shape as a function of loading. In the case of the NHT dummy load, the variation is about a harmless +/-0.25dB. 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. Note the SE-tube-like smooth increase in distortion over the whole power range. Also note that the distortion is less for a 4-ohm load. Total harmonic distortion plus noise as a function of frequency at several different power levels is plotted in Chart 3. Admirable is the low increase in distortion at the higher frequencies. Damping factor versus frequency is shown in Chart 4. A spectrum of the harmonic distortion and noise residue is plotted in chart 5 for an 8-ohm load. The AC-line harmonic spectrum is composed of odd harmonics, and there are some modulation effects of the line frequency around the second harmonic of the signal test frequency of 1kHz. The signal frequency harmonic components fall off in a nice manner with the second harmonic most dominant. This is said to have desirable sonic consequences.

Red line: open circuit
Magenta line: 8-ohm load
Blue line: 4-ohm load
Cyan line: NHT dummy-speaker load

(line up at 5W to determine lines)
Top line: 8-ohm SMPTE IM
Second line: 4-ohm SMPTE IM
Third line: 8-ohm THD+N
Bottom line: 4-ohm THD+N

4-ohm output loading
Cyan line: 160W
Blue line: 75W
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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