PSU question? Going tube rectified

sbelyo · 30th May 2006, 03:39 PM

I'm building this amp

The artice says the max output current is 20 ma

Here's the psu

I'd like to use a 5U4GB retifier because I have a bunch laying around and a 235-0-235 @270ma transformer. I put some values into PSU designer but I'm not shure about the rectifiers limits? How should I change the capacitors values so that it's within the rectifiers range?

poobah · 30th May 2006, 04:09 PM

Why do you consider it out of range at the moment?

I don't believe PSU II takes tube warm up into consideration when it sims. So you could ignore excess current messages during the first few seconds anyway.

BTW, 100 uF, seems off the charts for a headphone amp.

analog_sa · 30th May 2006, 05:29 PM

I may be wrong but i think 47uF is max for C1. C2/3 are fine.

SY · 30th May 2006, 05:37 PM

You are not wrong- the 100uF cap will kill that rectifier dead. 40uF is much more reasonable.

poobah · 30th May 2006, 05:41 PM

SY,

The Cath. Fol. output has good PSRR anyway doesn't it?

rdf · 30th May 2006, 06:08 PM

R1 and R2 are only 220 ohm. The parallel combination with the trailing 100 uF caps might make even 40uF for C1 a stretch. If you have the parts you might want to consider replacing R1 and R2 with chokes or going smaller for C1.

SY · 30th May 2006, 06:10 PM

I haven't tested mu followers, but presumably...

With proper grounding and reasonable filtering, getting the supply noise down should be no trouble anyway. The nice thing about the input cap limitation is that the ripple currents will be low.

Merlinb · 30th May 2006, 06:14 PM

Is it the in-rush current that limits the size of a capacitor after a valve rectifier? Is there a way to calculate the in-rush current- is it related to the time constant somehow?

SY · 30th May 2006, 06:40 PM

No, it's the peak ripple current that's the bad actor here.

sbelyo · 30th May 2006, 06:47 PM

I read on the 5U4GB data sheet that max input cap is 40uf so I'll change C1 to 40uf

Now C2, and C3 Is it okay to use say 150uf? And if I increase the value of the resistor, do I have to increase the wattage?

30th May 2006, 03:39 PM	#1
sbelyo diyAudio Member Join Date: May 2004 Location: East Coast	PSU question? Going tube rectified I'm building this amp The artice says the max output current is 20 ma Here's the psu I'd like to use a 5U4GB retifier because I have a bunch laying around and a 235-0-235 @270ma transformer. I put some values into PSU designer but I'm not shure about the rectifiers limits? How should I change the capacitors values so that it's within the rectifiers range?

30th May 2006, 05:37 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	You are not wrong- the 100uF cap will kill that rectifier dead. 40uF is much more reasonable. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

30th May 2006, 06:08 PM	#6
rdf diyAudio Member Join Date: Jun 2004 Location: big smoke	R1 and R2 are only 220 ohm. The parallel combination with the trailing 100 uF caps might make even 40uF for C1 a stretch. If you have the parts you might want to consider replacing R1 and R2 with chokes or going smaller for C1. __________________ Ears aren't microphones.

30th May 2006, 06:10 PM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	I haven't tested mu followers, but presumably... With proper grounding and reasonable filtering, getting the supply noise down should be no trouble anyway. The nice thing about the input cap limitation is that the ripple currents will be low. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

30th May 2006, 06:40 PM	#9
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	No, it's the peak ripple current that's the bad actor here. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

30th May 2006, 04:09 PM	#2
poobah diyAudio Member Join Date: Nov 2005	Why do you consider it out of range at the moment? I don't believe PSU II takes tube warm up into consideration when it sims. So you could ignore excess current messages during the first few seconds anyway. BTW, 100 uF, seems off the charts for a headphone amp.

30th May 2006, 05:29 PM	#3
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	I may be wrong but i think 47uF is max for C1. C2/3 are fine.

30th May 2006, 05:41 PM	#5
poobah diyAudio Member Join Date: Nov 2005	SY, The Cath. Fol. output has good PSRR anyway doesn't it?

30th May 2006, 06:14 PM	#8
Merlinb diyAudio Member Join Date: May 2006 Location: York	Is it the in-rush current that limits the size of a capacitor after a valve rectifier? Is there a way to calculate the in-rush current- is it related to the time constant somehow?

30th May 2006, 06:47 PM	#10
sbelyo diyAudio Member Join Date: May 2004 Location: East Coast	I read on the 5U4GB data sheet that max input cap is 40uf so I'll change C1 to 40uf Now C2, and C3 Is it okay to use say 150uf? And if I increase the value of the resistor, do I have to increase the wattage?

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