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Old 30th January 2007, 09:24 PM   #1
nhuwar is offline nhuwar  United States
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Default Optimal ripple voltage on b+ supply

I was wondering what is a good percent ripple to shoot for when designing my b+ supply filter.

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Nick
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Old 30th January 2007, 09:39 PM   #2
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I don't know about percent but under around 500mV should be fine, assuming it's push-pull.
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Old 30th January 2007, 09:46 PM   #3
SY is offline SY  United States
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That's dependent on which stage, what the PSR of the stage is, what the overall S/N requirement is...

For a raw supply, 5% ripple is a good figure. That's probably good enough for the plates of a p-p output stage. For more sensitive stages, you'll have to determine what your requirements are, then design appropriate filtering or regulation. A popular power supply design tool (and justifiably so) is PSUD2 from Duncan Amps.
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Old 30th January 2007, 10:32 PM   #4
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Quote:
Originally posted by SY
That's dependent on which stage, what the PSR of the stage is, what the overall S/N requirement is...

For a raw supply, 5% ripple is a good figure. That's probably good enough for the plates of a p-p output stage. For more sensitive stages, you'll have to determine what your requirements are, then design appropriate filtering or regulation. A popular power supply design tool (and justifiably so) is PSUD2 from Duncan Amps.
My only gripe with the program is that it doesn't understand how current loads from tubes gradually increase from 0 as they warm up... Stepping loads can only do so much to simulate this gradient in reality. It took me a lot of grief and warnings about negative current draw before someone explained this to me.
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Old 30th January 2007, 10:40 PM   #5
SY is offline SY  United States
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Yup, no question, software is no substitute for common sense. It's a nice tool, though, and the ripple predictions are damn accurate.
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Old 30th January 2007, 10:49 PM   #6
nhuwar is offline nhuwar  United States
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Thanks for the input I actually downloaded that app a while ago just havent used it yet. The power supply in question is pp final stage plate ps.

Oh Sy I should be getting the Morgan Jones book in 2 day's ordered it yesterday but amazon is very slow to ship things I've found.

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Nick
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Old 30th January 2007, 10:57 PM   #7
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Quote:
Originally posted by sorenj07
I don't know about percent but under around 500mV should be fine, assuming it's push-pull.
If push-pull when well balanced don't produce audible hum when idle it does not mean it does not intermodulate the signal and ripples.
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Old 30th January 2007, 11:28 PM   #8
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by sorenj07


My only gripe with the program is that it doesn't understand how current loads from tubes gradually increase from 0 as they warm up... Stepping loads can only do so much to simulate this gradient in reality. It took me a lot of grief and warnings about negative current draw before someone explained this to me.
I think you are talking about two separate issues. It is useful to know voltages for all possible operating conditions. When modeling circuits, I almost always use a current source for modeling. Then I look at the supply output with my target currents and with very small currents. I use the latter to determine the highest voltages any component will see, so that I won't have over voltage failures.

The step function is for modeling possible ringing behavior - a performance issue, not a safety issue. My understanding is rudimentary in this area, but it's good to check at least a couple of step changes, especially if you are using inductors in the supply.

My experience mirrors SY's as regards accuracy. This requires measuring your transformer primary and secondary resistance, as well as unloaded input and output.

Sheldon
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Old 30th January 2007, 11:39 PM   #9
nhuwar is offline nhuwar  United States
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I have actually just been playing with the program an with my current filter cap the output is remarkably clean but that doesn't mean i won't change it once I hear it.

what I have is 550 micro farad at 1000vdc but I dont know how to find the capacitors resistance.

Nick
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Old 31st January 2007, 01:15 AM   #10
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Quote:
Originally posted by nhuwar

what I have is 550 micro farad at 1000vdc but I dont know how to find the capacitors resistance.

Nick
wow, what kind of capacitor are you using? or is that a big capacitor network?
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