Distortion, and Power Supply Measurements
Retesting amp with powersupply instead of sissy lab powersupply and the distortion level has dropped from 0.17% to 0.11%.
Maybe the lab supply was causing compression due to current limiting circuit or maybe the lower rail voltages 22V of the lab supply is the reason.
Well the result is pleasing.
Redo FFT next and compare noise on output vs Firstwatt F5.
Retesting amp with powersupply instead of sissy lab powersupply and the distortion level has dropped from 0.17% to 0.11%.
Maybe the lab supply was causing compression due to current limiting circuit or maybe the lower rail voltages 22V of the lab supply is the reason.
Well the result is pleasing.
Redo FFT next and compare noise on output vs Firstwatt F5.
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Noise at output referenced to 2.82V rms (1W) output is around -96dB at 100Hz (rectified 50Hz AC)
Awesome result. I am bloody happy with that.
I can change the y axis and show power supply harmonics below 100dB if people are interested.
I will test Firstwatt F5 for comparison next.
Awesome result. I am bloody happy with that.
I can change the y axis and show power supply harmonics below 100dB if people are interested.
I will test Firstwatt F5 for comparison next.
Attachments
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The Vgs threshold of the N Channel parts I have, are 0.15V
and the P channel parts have a Vgs threshold of 0.55.
This leads to a situation with way more gain coming off the positive rail.
If you reduce the source resistance at J74 you increase the current through it which then lowers drain resistance required to turn on the mosfet and reduces gain.
If you increase Idss of J74 you make the situation even worse ie even more positive phase.
The only way to correct it is to use a lower idss J74 part, so that when you reduce source resistance at J74 the current doesn't increase too much.
I can simulate it if it helps.
and the P channel parts have a Vgs threshold of 0.55.
This leads to a situation with way more gain coming off the positive rail.
If you reduce the source resistance at J74 you increase the current through it which then lowers drain resistance required to turn on the mosfet and reduces gain.
If you increase Idss of J74 you make the situation even worse ie even more positive phase.
The only way to correct it is to use a lower idss J74 part, so that when you reduce source resistance at J74 the current doesn't increase too much.
I can simulate it if it helps.
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Good working!
I refer to this
https://www.diyaudio.com/forums/pass-labs/275921-watt-f7-review-100.html#post5131772
I refer to this
https://www.diyaudio.com/forums/pass-labs/275921-watt-f7-review-100.html#post5131772
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