Wednesday, December 13, 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: Unless otherwise noted, measurements were taken at a line voltage of 120V AC at the left-channel balanced input, with the Audio Precision AUX-0025 filter engaged.

Power output

  • Power output at 1% THD+N: 164.7W @ 8 ohms, 302.4W @ 4 ohms
  • Power output at 10% THD+N: 230.0W @ 8 ohms, 395.0W @ 4 ohms

Additional data

  • Input/output polarity: noninverting
  • AC-line current draw at idle: 14.0W, 0.23A, 0.51PF
  • Gain: output voltage divided by input voltage, 8-ohm load (Lch/Rch)
    • Balanced inputs: 15.36X, 23.7dB / 15.28X, 23.7dB
    • Unbalanced inputs: 30.81X, 29.8dB / 30.48X, 29.7dB
  • Input sensitivity for 1W output into 8 ohms (Lch/Rch)
    • Balanced inputs: 184mV / 185mV
    • Unbalanced inputs: 91.8mV / 92.8mV
  • Output impedance @ 50Hz: 0.018 ohm
  • Input impedance @ 1kHz
    • Balanced inputs: 21.4k ohms
    • Unbalanced inputs: 10.3k ohms
  • Output noise, 8-ohm load, balanced inputs terminated with 600 ohms, Lch/Rch
    • Wideband: 0.849mV/0.857mV, -70.5dBW/-70.4dBW
    • A weighted: 0.050mV/0.050mV, -95.0dBW/-95.0dBW
  • Output noise, 8-ohm load, unbalanced inputs terminated with 1k ohms, Lch/Rch
    • Wideband: 0.882mV/0.890mV, -70.1dBW/-70.0dBW
    • A weighted: 0.065mV/0.066mV, -92.8dBW/-92.6dBW
  • Output noise, 8-ohm load, without AP AUX-0025 filter, unbalanced and balanced inputs
    • Wideband: 498mV, -15.1dBW

Measurements summary

The Wadia a315 is a medium-power, two-channel, switching power amplifier that includes the latest Hypex Electronics Ncore technology.

Chart 1, which shows the a315’s frequency response into varying loads, was not sent through the Audio Precision AUX-0025 low-pass measuring filter. One of the interesting aspects of the Ncore technology is that the out-of-band high-frequency response is controlled by an output LCR filter in the overall feedback loop. Of interest in the shapes of the curves is that, just above 20kHz, the output impedance goes from normal positive (output drops with increasing load) to negative, with the greatest deviation of response at 40kHz, then passes through a close-to-zero output-impedance point at 60kHz, above which the output impedance becomes positive again. Within the audioband, the output impedance is low enough that there is negligible variation with the NHT dummy speaker load.

Chart 2 illustrates how the a315’s total harmonic distortion plus noise (THD+N) vs. power varies with 1kHz and SMPTE intermodulation test signals, and with 8- and 4-ohm loads. The level of distortion indicated is reasonably low.

THD+N as a function of frequency at different power levels is plotted in Chart 3. The increase in distortion with frequency is moderate. Still, the level of distortion is low over most of the power and frequency range.

Damping factor vs. frequency is shown in Chart 4. The damping factor remains moderately high throughout the audioband, and, unlike with most power amps, does not roll off severely above 500-1000Hz.

Chart 5 plots the spectrum of the harmonic distortion and noise residue of a 10W, 1kHz test signal. The AC line harmonics are low, their principal component being 60Hz. The signal harmonics are dominated by the second and third harmonics, with higher harmonics of rapidly decreasing magnitude.

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

chart2

(Line up at 50W 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 = 130W
Yellow line = 150W

Chart 4 - Damping factor as a function of frequency

Chart 4

Stereo mode
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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