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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.

These measurements were taken at 120V AC line voltage, both channels driven. Measurements were taken on both channels, using inputs 1 and 2. Unless otherwise noted, the data reported below are for the left channel.

Power output

  • Power output at 1% THD+N: 133.3W @ 8 ohms, 241.3W @ 4 ohms
  • Power output at 10% THD+N: 179.2W @ 8 ohms, 318.0W @ 4 ohms

Additional data

  • Input/output polarity (analog and digital): noninverting
  • AC-line current draw at idle: 95.0W, 1.06A, 0.65PF
  • Gain: output voltage divided by input voltage, 8-ohm load, Lch/Rch
    • Balanced inputs: 69.9X, 36.9dB / 69.7X, 36.9dB
    • Unbalanced inputs: 71.4X, 37.1dB / 71.1X, 37.0dB
  • Input sensitivity for 1W output into 8 ohms, Lch/Rch
    • Balanced inputs: 40.4mV / 40.6mV
    • Unbalanced inputs: 39.6mV / 36.7mV
  • Output impedance @ 50Hz: 0.2 ohm
  • Input impedance @ 1kHz
    • Balanced inputs: 37.5k ohms
    • Unbalanced inputs: 260.0k ohms
  • Output noise, 8-ohm load, balanced inputs terminated with 600 ohms, Lch/Rch
    • At reference volume setting
      • Wideband: 1.69mV / 0.815mV, -64.5dBW / -70.8dBW
      • A weighted: 0.161mV / 0.0764mV, -84.9dBW / -91.3dBW
    • At maximum volume
      • Wideband: 2.28mV / 2.09mV, -61.9dBW / -62.6dBW
      • A weighted: 0.407mV / 0.389mV, -76.6dBW / -77.2dBW
    • At minimum volume
      • Wideband: 4.23mV / 1.01mV, -56.5dBW / -68.9dBW
      • A weighted: 0.423mV / 0.106mV, -76.5dBW / -88.5dBW
  • Output noise, 8-ohm load, unbalanced inputs terminated with 1k ohms, Lch/Rch
    • At reference volume setting
      • Wideband: 1.67mV / 0.773mV, -64.6dBW / -71.3dBW
      • A weighted: 0.161mV / 0.0774mV, -84.9dBW / -91.3dBW
    • At maximum volume
      • Wideband: 1.40mV / 1.03mV, -66.1dBW / -68.8dBW
      • A weighted: 0.145mV / 0.0999mV, -85.0dBW / -91.0dBW
    • At minimum volume
      • Wideband: 4.24mV / 1.02mV, -56.5dBW / -68.9dBW
      • A weighted: 0.393mV / 0.106mV, -77.1dBW / -88.5dBW

Measurements summary

Gryphon Audio Designs’ Diablo 120 integrated amplifier builds on the ten-year-long success of Gryphon’s Diablo 300 model.

Chart 1 shows the frequency response of the Diablo 120 with varying loads. The output impedance is low enough that there was negligible variation with the NHT dummy speaker load.

Chart 2 illustrates how the Diablo 120’s total harmonic distortion plus noise (THD+N) vs. power varied for 1kHz and SMPTE IM test signals and amplifier output for 8- and 4-ohm loads. Note that Gryphon claims to use zero overall feedback in the Diablo 120; the levels of distortion, though higher than in most feedback designs, are still reasonable.

The Diablo 120’s THD+N as a function of frequency at a number of increasing power levels is plotted in Chart 3. The levels of increase are moderate.

The Gryphon’s damping factor vs. frequency, plotted in Chart 4, is unusual in its relative flatness. This is a natural consequence of the absence of any overall negative feedback being used, and of not having a series inductor in an output-stabilizing network.

Chart 5 plots the Diablo 120’s spectrum of THD+N residue of a 10W, 1kHz test signal. The AC line harmonics are very low but relatively complex. The signal harmonics are dominated by the second and third harmonics, with higher harmonics of decreasing magnitude.

Some key measurements of the Diablo 120’s digital section were taken. Its AES input was fed with a full-scale 0dBFS digital signal level, and the main amplifier outputs were set as close to 5W/8 ohm as possible with the volume control. Chart 6 shows the frequency response with both of the filter settings, Slow and Fast.

Chart 7 plots the results of a revealing test that I always do on DACs: measure the output amplitude of a 1kHz signal with a 1kHz bandpass filter at full-scale digital level with decreasing input signal level, down to where the output level meets the noise floor. This reveals that the Diablo 120’s noise floor in this test was about -110dBFS, which is pretty good for 24-bit input data.

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
Cyan line = NHT dummy-speaker load

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

Chart 2

(Line up at 30W 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 = 120W

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 AES/EBU digital input at amplifier output

Chart 6

Slow filters
Red line = 44.1kHz
Magenta line = 96kHz
Yellow line = 192kHz

Fast filters
Cyan line = 44.1kHz
Green line = 96kHz
Blue line = 192kHz

Chart 7 - DAC input/output linearity of both channels

Chart 7

24-bit/44.1kHz resolution with 1kHz bandwidth filter
Red line = left channel
Magenta line = right channel

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