Wednesday, September 20, 2017


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.

Measurements were taken at 120V AC line voltage with both channels driven, and on both channels using balanced inputs. Unless otherwise noted, all results cited are for the left channel. The integrated amplifier reference volume setting was 500mV input (5W/8-ohm power output).

Power output

  • Output power at 1% THD+N: 231.1W @ 8 ohms, 468.3 @ 4 ohms
  • Output power at 10% THD+N: 281.3W @ 8 ohms, 564.7W @ 4 ohms

Additional data

  • This amplifier does not invert polarity.
  • AC line current draw at idle: 1.02A, 0.63PF, 78.0W
  • Gain: output voltage divided by input voltage
    •      Unbalanced inputs: 44.5X, 33.0dB
    •      Balanced inputs:  44.5X, 33.0dB 
  • Input sensitivity for 1W output into 8 ohms
    •      Unbalanced inputs: 43.5mV
    •      Balanced inputs: 43.5mV
  • Output impedance @ 50Hz: 0.015 ohm
  • Input impedance @ 1kHz
    •      Unbalanced inputs: 6.7k ohms
    •      Balanced inputs: 9.7k ohms
  • Output noise, reference conditions, balanced inputs, termination 600 ohms, Lch/Rch
    •      Wideband: 0.561mV/0.580mV, -74.1dBW/-73.8dBW
    •      A weighted: 0.0745mV/0.0862mV, -91.6dBW/-90.3 dBW
  • Output noise, reference conditions, unbalanced inputs, termination 1k ohm, Lch/Rch
    •      Wideband: 0.546mV/0.569mV, -74.3dB/-73.9dBW
    •      A weighted: 0.0706mV/0.0803mV, -92.1dBW/-90.4dBW
  • Output noise, 8-ohm load, volume at maximum, balanced inputs, termination 600 ohms, Lch/Rch
    •      Wideband: 0.652mV/0.707mV, -72.4dBW/-72.0dBW
    •      A weighted: 0.155mV/0.141mV, -87.8dBW/-86.1dBW
  • Output noise, 8-ohm load, volume at maximum, unbalanced inputs, termination 1k ohm, Lch/Rch
    •      Wideband: 0.410mV/0.457mV, -76.8dBW/-75.8dBW
    •      A weighted: 0.0618mV/0.0784mV, -93.2dBW/-91.1dBW
  • Output noise, 8-ohm load, volume at minimum, balanced inputs, termination 600 ohms, Lch/Rch
    •      Wideband: 0.403dBW/0.422mV, -76.9dBW/-76.5dBW
    •      A weighted: 0.0533mW/0.0655mV, -94.5dBW/-92.7dBW
  • Output noise, 8-ohm load, volume at minimum, unbalanced inputs, termination 1k ohm, Lch/Rch
    •      Wideband: 0.405mV/0.422mV, -76.9dBW/-75.5dBW
    •      A weighted: 0.0533mV/0.0645mV, -94.5dBW/-92.8dBW

Measurements summary

The H360 DAC-integrated amplifier builds on the success of Hegel’s H300, adding network-playing capability and AirPlay. The power outputs of the two models are similar.

Chart 1 shows the frequency response of the H360 with varying impedance loads. The output impedance is low enough that there was negligible variation with the NHT dummy speaker load.

Chart 2 illustrates how the H360’s total harmonic distortion plus noise (THD+N) vs. power varies for 1kHz and SMPTE intermodulation test signals and amplifier output for 8- and 4-ohm loads.

Chart 3 plots the THD+N as a function of frequency at several different power levels. As the power level is increased, the increase in distortion with frequency is quite pronounced.

The H360’s damping factor vs. frequency is shown in Chart 4. Like the H300, the H360 shows a typical decrease as the frequency increases, but with a surprising decrease at low frequencies. Perhaps Hegel has discovered something by having this characteristic -- that it possibly improves the sound?

A spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal is plotted in Chart 5. The AC-line harmonics are low but relatively complex. The signal harmonics are dominated by the third harmonic, with second and higher harmonics of decreasing magnitude.

Some key measurements were taken of the H360’s digital section. The Coax 1 input was fed a full-scale, 0dBFS digital signal and the main amplifier outputs were set as close to 5W/8 ohms as possible with the volume control. At a sample rate of 192kHz, the frequency response was the same as at a sample rate of 96kHz. I have seen this behavior in a few other DACs. This means that files at sample rates of 176.4 and 192kHz won’t be played back with the extended high-frequency response such files can contain. Chart 6 is a plot of this response.

A revealing test that I always do on a DAC is to measure the THD+N of a 1kHz signal in a 20Hz-22kHz bandwidth at full-scale digital level with decreasing input signal level, down to where the distortion disappears into the noise floor. Doing this revealed that the H360’s noise floor was about -84dBFS, which is equivalent to about 0.42mV, -76.6dBW of output noise dominated by AC-line harmonics. This is somewhat more than with the analog inputs.

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 10W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

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

Chart 3

(8-ohm loading)
Red line = 1W
Magenta line = 10W
Blue line = 30W
Cyan line = 70W
Green line = 200W

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 an 8-ohm load

Chart 6 - Frequency response of Coax 1 digital input at amplifier output

Chart 5

Red line = 44.1kHz
Magenta line = 96 and 192kHz

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