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Old 24th March 2013, 02:14 PM   #1841
DF96 is offline DF96  England
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Energy in joules = 0.5 x C x V^2
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Old 24th March 2013, 02:29 PM   #1842
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Originally Posted by DF96 View Post
Energy in joules = 0.5 x C x V^2
Thanks a lot !
no ... I was wrong. I checked roughly and more or less there is the same stored energy (higher V but also much less uF in the tube amps)
Thanks again
Regards,
gino
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Old 26th March 2013, 11:40 PM   #1843
gootee is offline gootee  United States
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Just for fun, I fixed the method used to calculate the reservoir capacitance required for a sine output from a class AB power amplifier, at the clipping threshold, for the case when the signal frequency is greater than or equal to the AC mains frequency. I will post a corrected spreadsheet, sometime soon.

Still need to also re-work the case for signal frequeny less than the mains frequency, which currently is wrong and gives capacitances that are too low (probably by 10%-25%). I think I know how, but haven't had the time, yet.

Last edited by gootee; 26th March 2013 at 11:42 PM.
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Old 26th March 2013, 11:47 PM   #1844
fas42 is offline fas42  Australia
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You amaze me, Tom, with the energy you're putting into this! Thanks for doing it, I hope to be inspired to do something likewise ...

Cheers,
Frank
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Old 27th March 2013, 03:00 AM   #1845
gootee is offline gootee  United States
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Hi Frank. Well, the sine-only part isn't really important (since the DC@peak vs rated power stuff solves the original problem very well). But it's one of those things I just want to do. It's like a certain type of puzzle that I like to try to solve, just for the love of trying. For me, it's similar to going out in the woods and hunting for Morel mushrooms, or working "Killer Sudoku" puzzles (see krazydad.com). Also, even though the math isn't even close to what I used to be able to do, back in, say, 1980, it still kind-of makes me feel young again, to relearn some small parts of it.
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Old 27th March 2013, 03:33 AM   #1846
gootee is offline gootee  United States
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Well, I posted that document too soon. Wish I had more time for this stuff.

It turns out that the sine-only calculations that I said were good for f_signal >= f_mains are really only good up to 2*f_mains, i.e. 2*f_mains >= f_signal >= f_mains.

Back to the drawing board...

Sorry about that.
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Old 27th March 2013, 10:09 PM   #1847
fas42 is offline fas42  Australia
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Not really something to worry about, but as a demonstration of what's possible if you absolutely must have the lowest power supply impedance at very high frequencies, the ultimate decoupling strategy so to speak, there's this: http://www.sanmina.com/pdf/solutions...nical_0106.pdf.

The strategy, and precision required, is very different from that of audio circuits, but it gets results for supply impedance: 10 milliohms at 100Meg, 100 milliohms at 1GHz.

Frank
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Old 27th March 2013, 10:27 PM   #1848
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Originally Posted by AndrewT View Post
This seems unusually high.
The pics I have seen all support a MUCH shorter conduction period.
Even the saw tooth ripple on the smoothing caps shows a MUCH shorter conduction period.
Are you looking at both peaks? 60/360 = 16.66..%
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Old 27th March 2013, 10:36 PM   #1849
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Does a snubber designed bridge rectifier increase the conduction angle, or is there no effect from the snubbers around the diodes? I am talking about a capacitor resistor snubber design.
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Old 28th March 2013, 02:25 AM   #1850
gootee is offline gootee  United States
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No. Snubbers do not usually appreciably change the conduction angle. They might typically shorten it by just a hair.
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