Hi
I am trying to understand more about tube amps so I can eventually do some modifications to my own tube amp.
Do the power supply capacitors also need to be rated according to B+? So let's say B+ is 180V, are 180V of current going through the power supply capacitors or does it become 180V after it has already passed through them (if that makes any sense)?
I am in Europe so voltage from the wall would be 230V.
Cheers
I am trying to understand more about tube amps so I can eventually do some modifications to my own tube amp.
Do the power supply capacitors also need to be rated according to B+? So let's say B+ is 180V, are 180V of current going through the power supply capacitors or does it become 180V after it has already passed through them (if that makes any sense)?
I am in Europe so voltage from the wall would be 230V.
Cheers
The B+ voltage is in fact the DC voltage on the power supply capacitor connected there.
The input current from the transformer and diodes keeps the capacitor charged to the nominal voltage,
while the output tubes drain the charge. For a constant charge on the capacitor, the voltage V = Q /C,
where Q is the charge on the capacitor plate, and C is the rated capacity of the capacitor in Farads.
On average, the charge (and voltage) remain about constant, although there is some ripple in the DC voltage,
since the charging is not constant but occurs in pulses twice during every AC power line cycle.
You may want to experiment with this program to get a better idea of how it works.
https://www.duncanamps.com/psud2/
The input current from the transformer and diodes keeps the capacitor charged to the nominal voltage,
while the output tubes drain the charge. For a constant charge on the capacitor, the voltage V = Q /C,
where Q is the charge on the capacitor plate, and C is the rated capacity of the capacitor in Farads.
On average, the charge (and voltage) remain about constant, although there is some ripple in the DC voltage,
since the charging is not constant but occurs in pulses twice during every AC power line cycle.
You may want to experiment with this program to get a better idea of how it works.
https://www.duncanamps.com/psud2/
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i also look at what the unloaded voltage would be when no tubes are not inserted, that will be my vdc rating for filter caps, specially the first one after the rectifier...
indeed, but here you get correct technical information, my rule of thumb is 80% of voltage rating, for example, a 100vdc cap would be good up to 80 to 85 volts, why? imagine you operate that to say 99vdc and the there was a primary line voltage surge, what do you think happens?
You clearly meant "no OTHER tubes". But what you said is confusing.
So what resistor value he should use as a load between B+ and ground to simulate a tube. At least in psud2 ?
Assuming the most demanding SS bridge topology will ask secondary transformer VAC x 1.41 voltage rating to choose the voltage rating and add the 20% for better life span. Say the secondary is 230 Vac, you got circa 390 Vdc which ask a 400 Vdc rated cap.
Minimalist answer for security again as involving the most demanding need i.e. 4 rectyfing diodes. Looks like the op did not understand this is not the load that dictate the cap voltage rating as he talked about voltage. But maybe he wanted to ask about capacitance in relation to load need. At this level the first answer should be to avoid him to put his hands first in HV power supply before having a better understanding cause it is possibly lethal. At least my feeling as a non native english reader in relation to the question and a technical noob myself.
As a technical noob myself this us what I understood from the question between lines.
There is a pdf from Hammond about secondary power traffo and rectifier w and w/o center tape topologies to see how voltage is outputed.
Assuming the most demanding SS bridge topology will ask secondary transformer VAC x 1.41 voltage rating to choose the voltage rating and add the 20% for better life span. Say the secondary is 230 Vac, you got circa 390 Vdc which ask a 400 Vdc rated cap.
Minimalist answer for security again as involving the most demanding need i.e. 4 rectyfing diodes. Looks like the op did not understand this is not the load that dictate the cap voltage rating as he talked about voltage. But maybe he wanted to ask about capacitance in relation to load need. At this level the first answer should be to avoid him to put his hands first in HV power supply before having a better understanding cause it is possibly lethal. At least my feeling as a non native english reader in relation to the question and a technical noob myself.
As a technical noob myself this us what I understood from the question between lines.
There is a pdf from Hammond about secondary power traffo and rectifier w and w/o center tape topologies to see how voltage is outputed.
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Anything from 2Megs to 200 Ohms. He has not said WHAT kind of "tube amp" he is asking about. We'd want voltage AND current.
for tube power amps, depending on the type of output tubes used, datasheet information showed plenty of operating points. class A would be a more constant load compared to class AB..
Good practice, as usually the capacitors see that scenario on every startup before the tubes start to conduct.