Friday, September 22, 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.

Note: Measurements were made at 120V AC line voltage and through the balanced input unless otherwise noted.

Power output

  • Output power at 1% THD+N: 355.2W @ 8 ohms, 520.7W @ 4 ohms
  • Output power at 10% THD+N: 447.2W @ 8 ohms, 663.1W @ 4 ohms

Additional data

  • This amplifier does not invert polarity.
  • AC-line current draw at idle: 1.39A, 0.64PF, 105W
  • Gain: output voltage divided by input voltage, 8-ohm load
    •      Unbalanced inputs: 31.4X, 29.9dB
    •      Balanced inputs: 30.4X, 29.7dB
  • Input sensitivity for 1W output into 8 ohms
    •      Unbalanced inputs: 91.1mV
    •      Balanced inputs: 93.0mV
  • Output impedance @ 50Hz: 0.026 ohm
  • Input impedance @ 1kHz
    •      Unbalanced inputs: 10.8k ohms
    •      Balanced inputs: 50.5k ohms
  • Output noise, 8-ohm load, unbalanced inputs, termination 1k ohm
    •      Wideband: 0.175mV, -84.2dBW
    •      A weighted: 0.042mV, -96.6dBW
  • Output noise, 8-ohm load, balanced inputs, termination 600 ohms
    •      Wideband: 0.991mV, -69.1dBW
    •      A weighted: 0.188mV, -83.6dBW

Measurements summary

The Jones Audio PA-M300 Series 2 is a high-powered, solid-state, monoblock power amplifier.

Chart 1 shows the frequency response of the PA-M300 with varying loads. The response is quite wideband, with a -3dB point of over 200kHz. Although the NHT dummy load shows no appreciable variation in the audioband, it does have some visible effect above 50kHz.

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 and how it rises with output level is typical of most solid-state power amplifiers, except that the IM distortion is not materially higher than the harmonic distortion. Also of note: The low-power THD+N with the unbalanced input (not shown) is quite a bit lower due to that input’s lower noise.

Chart 3 plots THD+N as a function of frequency at several different power levels. The amount of increase in distortion at high frequencies is very pronounced as the power level rises.

Damping factor vs. frequency, shown in Chart 4, is of a value and nature typical of many solid-state amplifiers: high up to about 1kHz, then rolling off with increasing frequency.

Chart 5 plots the spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal. The magnitude of the AC-line harmonics is relatively complex, with mostly odd harmonics of 60Hz extending way up into the midrange. Signal harmonics are low, with the second, third, and fifth harmonics being visible in the spectrum.

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

Chart 1

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

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

Chart 2 

(Line up at 100W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 4-ohm THD+N
Third line = 8-ohm SMPTE IM distortion
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 = 150W
Cyan 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 an 8-ohm load

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