Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: AmberB on February 15, 2022, 07:53:22 pm
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I just have a quick question about the power supply for that SE amp that I want to build. I would like to have 2 stages of filter capacitor before I take the B+ for the power tube plate. I want to lower the amount of ripple going to the power tube plate. I'll be using diodes for the rectifier.
I have a variety of power resistors that I can choose from to put between the first and second cap. If I use two 50uf caps for the first 2 stages, can I get away with putting a 470 ohm resistor between them, or do I need something bigger, such as a 1000 ohm resistor.
I haven't made very many single ended amps, and the ones that I did make use a 5Y3 tube, so this is my first SS rectified SE amp.
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You can use a 470 or even smaller if you want. But for even better ripple reduction I recommend using a choke.
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I did this on a 20w single ended build. Used a Hammond 158Q for my build. Only 100 ohms. Lots of Hammond choke models and specs here. The higher the resistance on the choke the more voltage you will drop before you get to the power tube plate node.
https://www.hammfg.com/electronics/transformers/choke/153-159
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what power tube(s) are you using?
for my 6l6g-powered 'big boy' vibrochamp i used one of these: https://www.mojotone.com/Filter-Choke-for-6L6-Amps-125C1A (well, i used the magnetic components ones antique electronic supply used to stock for around the same price)
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what power tube(s) are you using?
for my 6l6g-powered 'big boy' vibrochamp i used one of these: https://www.mojotone.com/Filter-Choke-for-6L6-Amps-125C1A (well, i used the magnetic components ones antique electronic supply used to stock for around the same price)
I'm planning on using a 6SN7, both plates in parallel, for the power tube to start with. If it's not loud enough, I'll probably rewire the octal socket for a 6V6. The transformers can handle the 6V6, I just want to see what I get when using the 6SN7. The output transformer is about 9600 ohms at 4 ohms load, so it should work for either tube.
As for the choke, I thought about that, but I would have to buy one and I'm trying to build the amp with stuff I already have. I know that a choke suitable for this amp isn't very expensive, but still...
I have 2 different "super champ" type amps that I've built from small pa amps that used a 6L6 single ended, and those both work well. I took the plate voltage off the first power supply cap on those. This new amp is an experiment to see what I get.
This little amp will have about 400 volts on the plate, so the 6SN7 is the only suitable twin triode tube that I know of to try this with.
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Sounds like you got a clear direction on what you want to do and the answer you need to proceed. A resistor will be fine between those first two caps. My SE amp was designed and built that way and I played it for years like that. It was only recently I got on a hum kick and decided to replace it with a choke. Can always source a choke with a similar value of resistance to make it a 1:1 swap down the road. Or if you find yourself needing to manipulate voltage, get a choke with specs based on that.
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Keep an eye on your 6.3 volt readings.
Your not going to draw much current and I suspect unless you have a very low current 6.3v winding, your 6.3 will be more like 7.5v , not good for tube life.
You might pull 600 milliamps at 6.3v but if your winding is say, 3amps at 6.3 volts, then your heaters may be way to high.
Something to consider.
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Keep an eye on your 6.3 volt readings.
Your not going to draw much current and I suspect unless you have a very low current 6.3v winding, your 6.3 will be more like 7.5v , not good for tube life.
You might pull 600 milliamps at 6.3v but if your winding is say, 3amps at 6.3 volts, then your heaters may be way to high.
Something to consider.
Yes, that is a good thing to keep in mind. If I need to, I probably could calculate a load resistor to bring the voltage within line.