Alternate First Watt Power Supply Schematic - Page 19

darrr · 30th December 2020, 10:08 PM

@JeffYoung
You probably have an ltspice model. I have a request to You. Could you check what the 100hz ripple will be in this configuration: 33000uF capacitors and 0.47R resistors? Now the ripple is 170mVpp. Rail voltages under load +/- 21.7VDC from 18VAC on secondaries. Maybe it will be better?

JeffYoung · 3rd January 2021, 07:21 PM

SPICE predicts 75mVpp.

darrr · 3rd January 2021, 08:28 PM

Thank you Jeff

Do I correctly suspect there will be a bigger voltage drop?
Regards and Happy New Year

JeffYoung · 3rd January 2021, 09:08 PM

Yes, but not material (~0.05V).

If you're willing to lose some voltage, 1 ohm resistors will nearly halve the ripple again at the loss of about 0.25V.

darrr · 4th January 2021, 09:28 PM

I have one more board so I can make a better version without desoldering. I wonder whether to install 4pcs 33000uF capacitors before the resistors and 47000uF on each rail after them . Will it be quieter than all 33mF versions?

JeffYoung · 4th January 2021, 09:48 PM

SPICE says 60mV w/0R47s; 35mV w/1R0s.

darrr · 4th January 2021, 10:09 PM

Is there any danger of increasing the capacity and resistance in the filter?

JeffYoung · 4th January 2021, 10:30 PM

More resistance leads to lower-voltage rails and more heat in the resistors.

More capacitance before the resistors puts more of a tax on the transformer (and fuses if you don't have a thermistor or other form of soft-start).

More capacitance after the resistors does too, but to a lesser effect.

darrr · 10:42 PM

Thank you Jeff.
I was thinking about a slb power supply but the costs will be much higher with a new transformer so I will work on your project

4th January 2021, 10:39 PM	#189
darrr diyAudio Member Join Date: Jan 2018 Location: Poland	Thank you Jeff. I was thinking about a slb power supply but the costs will be much higher with a new transformer so I will work on your project Last edited by darrr; 4th January 2021 at 10:42 PM.

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30th December 2020, 10:08 PM	#181
darrr diyAudio Member Join Date: Jan 2018 Location: Poland	@JeffYoung You probably have an ltspice model. I have a request to You. Could you check what the 100hz ripple will be in this configuration: 33000uF capacitors and 0.47R resistors? Now the ripple is 170mVpp. Rail voltages under load +/- 21.7VDC from 18VAC on secondaries. Maybe it will be better?

3rd January 2021, 07:21 PM	#182
JeffYoung diyAudio Member Join Date: Jul 2017 Location: Ireland	SPICE predicts 75mVpp.

3rd January 2021, 08:28 PM	#183
darrr diyAudio Member Join Date: Jan 2018 Location: Poland	Thank you Jeff Do I correctly suspect there will be a bigger voltage drop? Regards and Happy New Year

3rd January 2021, 09:08 PM	#184
JeffYoung diyAudio Member Join Date: Jul 2017 Location: Ireland	Yes, but not material (~0.05V). If you're willing to lose some voltage, 1 ohm resistors will nearly halve the ripple again at the loss of about 0.25V.

4th January 2021, 09:28 PM	#185
darrr diyAudio Member Join Date: Jan 2018 Location: Poland	I have one more board so I can make a better version without desoldering. I wonder whether to install 4pcs 33000uF capacitors before the resistors and 47000uF on each rail after them . Will it be quieter than all 33mF versions?

4th January 2021, 09:48 PM	#186
JeffYoung diyAudio Member Join Date: Jul 2017 Location: Ireland	SPICE says 60mV w/0R47s; 35mV w/1R0s.

4th January 2021, 10:09 PM	#187
darrr diyAudio Member Join Date: Jan 2018 Location: Poland	Is there any danger of increasing the capacity and resistance in the filter?

4th January 2021, 10:30 PM	#188
JeffYoung diyAudio Member Join Date: Jul 2017 Location: Ireland	More resistance leads to lower-voltage rails and more heat in the resistors. More capacitance before the resistors puts more of a tax on the transformer (and fuses if you don't have a thermistor or other form of soft-start). More capacitance after the resistors does too, but to a lesser effect.