Wednesday, October 18, 2017

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All amplifier measurements are performed independently by BHK Labs. All measurement data and graphical information displayed below are the property of the SoundStage! Network and Schneider Publishing Inc. Reproduction in any format is not permitted.

Note: Measurements were made at 120V AC line voltage with both channels being driven. Measurements made on left channel through the balanced inputs unless otherwise noted.

Power output

  • Output power at 1% THD+N: 216W @ 8 ohms, 381W @ 4 ohms
  • Output power at 10% THD+N: 276W @ 8 ohms, 472W @ 4 ohms

Additional data

  • This amplifier does not invert polarity.
  • AC-line current draw at idle: 1.3A, 0.61PF, 97W
  • Gain: output voltage divided by input voltage for unbalanced and balanced inputs: 40.5X, 32.5dB 
  • Input sensitivity for 1W output into 8 ohms, unbalanced and balanced inputs: 69.8mV
  • Output impedance @ 50Hz: 0.018 ohm
  • Input impedance @ 1kHz
    •      Unbalanced inputs: 45.5k ohms
    •      Balanced inputs: 9.4k ohms
  • Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm, Lch/Rch
    •      Wideband: 0.32mV/0.32mV, -78.9dBW/-78.9dBW
    •      A weighted: 0.067mV/0.041mV, -92.5dBW/-96.8dBW
  • Output noise, 8-ohm load, balanced inputs, termination 600 ohms, Lch/Rch
    •      Wideband: 0.58mV/0.59mV, -73.7 dBW/-73.6dBW
    •      A weighted: 0.11mV/0.10mV, -88.2dBW/-89.0dBW

Measurements summary

The H20, a medium-powered solid-state stereo power amplifier, is the smallest of three models in the Hegel line.

Chart 1 shows the frequency response of the H20 with varying loads. The high-frequency response is wide, with an approximate 3dB-down point beyond 200kHz. The frequency response is quite invariant with load over the audioband, and so the response with the NHT dummy-speaker load is not shown in this chart. Of note, this design includes a low-frequency rolloff.

Chart 2 illustrates how total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE IM test signals and amplifier output for 8- and 4-ohm loads. The amount of distortion is dominated by noise up to perhaps 10W, then rises as distortion per se at higher power, up to clipping. 

Chart 3 plots THD+N as a function of frequency for 4-ohm loading and at several different power levels. The apparent increase in distortion at high frequencies is admirably low. 

The H20’s damping factor vs. frequency (Chart 4) is typical of that of many solid-state amplifiers: high up to about 1kHz, then rolling off with increasing frequency. At low frequencies, however, the effect of what causes the low-frequency rolloff also affects the output impedance, and causes the damping factor to decrease below 100Hz. 

Chart 5 shows the spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal. The AC-line harmonics are relatively low in level but complex in nature. Signal harmonics are about equally second and third; the fourth and fifth harmonics are somewhat lower in level.

Chart 1 - Frequency response of output voltage as a function of output loading

Chart 1

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

Chart 2 - Distortion as a function of power output and output loading

Chart 2 

(Line up at 100W to determine lines)
Top line = 8-ohm SMPTE IM distortion
Second line = 4-ohm SMPTE IM distortion
Third line = 8-ohm THD+N
Bottom line = 4-ohm THD+N

Chart 3 - Distortion as a function of power output and frequency

Chart 3

(4-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 70W
Cyan line = 150W
Green line = 300W

Chart 4 - Damping factor as a function of frequency

Chart 4

Damping factor = output impedance divided into 8

Chart 5 - Distortion and noise spectrum

Chart 5

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

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