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?
An externally hosted image should be here but it was not working when we last tested it.
The artice says the max output current is 20 ma
Here's the psu
An externally hosted image should be here but it was not working when we last tested it.
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?
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.
😉
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.
😉
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.
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.
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.
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?
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?
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?
Sure... 150 uF is fine.
MerlinB,
As the the input cap gets larger, the diode conducts for a shorter duration of time (conduction angle). Equal energy, in less time, means more current. Instead of "ripple current"... think of it has "peak charging current". This current kills the diode. Inrush is not a problem because the tube diode wakes up slowly.
😉
MerlinB,
As the the input cap gets larger, the diode conducts for a shorter duration of time (conduction angle). Equal energy, in less time, means more current. Instead of "ripple current"... think of it has "peak charging current". This current kills the diode. Inrush is not a problem because the tube diode wakes up slowly.
😉
Knowing nothing about designing tube gear, be it PSU or whatever. But how about replacing R1 and R2 with some cheap chokes?
SY and the other guys here know if it's worth it.
SY and the other guys here know if it's worth it.
Hi phn,
Cheap chokes are what happens when your kid throws the cordless phone into the swimming pool or knocks the Weber (popular American outdoor cooking grill) over loaded with ribeyes (expensive and tender beef steak).
Chokes find their advantage ($$) when the wattage levels go up.
😉
Cheap chokes are what happens when your kid throws the cordless phone into the swimming pool or knocks the Weber (popular American outdoor cooking grill) over loaded with ribeyes (expensive and tender beef steak).
Chokes find their advantage ($$) when the wattage levels go up.
😉
poobah said:
I don't normally disagree with the furry one (!), but I still recommend running these values through PSUD before hanging 40uF plus another resistor-isolated 300uF off that rectifier. 220 ohms feels low.
Hi rdf,
Great idea... How's the wet coast?
sbelyo,
Are you designing to meet a certain spec for PSU ripple? The bigger is better mentality is all good... this IS about fanatics after all. But, there is always a cost or problem when overkill is at work.
😉
Great idea... How's the wet coast?
sbelyo,
Are you designing to meet a certain spec for PSU ripple? The bigger is better mentality is all good... this IS about fanatics after all. But, there is always a cost or problem when overkill is at work.
😉
My target voltage is a B+ of 250V
I ran it through psu designer with a 235-0-235 full wave 5u4gb
C(40uf)R(1.1K)C(300uf) and a 20ma constant current draw and got like 251 Volts max at l1
is that what I should be looking at?
I ran it through psu designer with a 235-0-235 full wave 5u4gb
C(40uf)R(1.1K)C(300uf) and a 20ma constant current draw and got like 251 Volts max at l1
is that what I should be looking at?
Yes,
But also you should be looking at ripple voltage as well. Look at the min and max voltages of your final cap. The difference between these two is the ripple voltage and that could be audible. Larger caps will reduce this voltage; buit also increase currents... it is a comprimise you must balance.
Try experimenting with a larger resistor & smaller caps as rdf suggested. If your supply comes out at 240 Volts, that will make very little difference in the sound, if any. A ten fold reduction in ripple could make a real difference.
Do you have a specification for the desired ripple voltage>? What caps were in the original design?
😉
But also you should be looking at ripple voltage as well. Look at the min and max voltages of your final cap. The difference between these two is the ripple voltage and that could be audible. Larger caps will reduce this voltage; buit also increase currents... it is a comprimise you must balance.
Try experimenting with a larger resistor & smaller caps as rdf suggested. If your supply comes out at 240 Volts, that will make very little difference in the sound, if any. A ten fold reduction in ripple could make a real difference.
Do you have a specification for the desired ripple voltage>? What caps were in the original design?
😉
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