Curious about Power output Increase Hafler DH-120

While repairing another Hafler DH-120, I decided to experiment with different outputs. I initially replaced the original outputs on one channel with Exicon T03 10N series mosfets.
They work well and operate very similar to the stock outputs (2sk134, 2sj49). The basic rating for the 10 series Exicon is 8A / 125W. Power clipping for each channel ended up nearly identical at 24.2V RMS or 73 watts. I had some EFC20 series (Double Die Version) and installed them in both channels, out of curiosity, reset the bias and re-measured the output.
Both channels clipped at 27.8V RMS or 95 watts. Distortion measured with REW was similar to the 10N series or stock outputs at about .009 THD.
The rating for the 20N series Exicons is 16A 250W. My rail voltages measured 54 v both channels. Close to the Hafler manual spec.

Why would the power increase by just changing outputs? I thought that would only be dependent on drive stage gain and rail voltages.

Measured with 8 ohm load at 1kHz.

To sum up... the 10N series Exicon outputs had an almost identical clipping point to the stock outputs, but there was an increase in the clipping output with the 20N double die outputs.

Just curious!


  • EFC 10.png
    EFC 10.png
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  • EFC 20.png
    EFC 20.png
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