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More help with low watt output stage please
More help with low watt output stage please
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Old 22nd July 2021, 02:47 AM   #31
Chris Hornbeck is offline Chris Hornbeck  United States
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Why is there a voltage divider at the intersection of first and second stages of the preamp? Also, why the double output capacitors?


Calculation of gain reduction by feedback should be a factor of (21.2 + 4.9) / 21.2 = 1.23 or about a smidgen in dBs.


All good fortune,
Chris
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Old 22nd July 2021, 03:19 AM   #32
gary h is offline gary h  United States
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Thank you Fuling, I think I had the grid leak and grid stopper resistors backwards. Chris, is that the voltage divider you are referring to? I will clean this up in next version. As far as the two output caps, a feature of the Aikido pcb is that it affords room for two or three different output caps. I neglected to draw in the switch that selects 1,2, or both. Currently I have a paper and poly cap. I cant tell the difference between them, so I like to think they both sound good.
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Old 22nd July 2021, 04:08 AM   #33
gary h is offline gary h  United States
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Now I re read your question, you are aking about the voltage divider within the preamp. I will not do justice to that question, but I will happily refer you to the tubecad notes that explain. As far as I ca discern, it has something to do with the way the Akido circuit cancels out PS noise by playing two halves of each triode against the other. I will look for the link that explains
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Old 22nd July 2021, 04:11 AM   #34
gary h is offline gary h  United States
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By the way Chris, would you care to reflect on the meaning (to you) of your tag line. Every time I read it, I think of a guy in a white wig noticing the similarities between curious electrical phenomenon and human behavior.
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Old 22nd July 2021, 04:36 AM   #35
gary h is offline gary h  United States
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I believe the answer to your question about the preamp circuit lies here:

New Tube Circuit: The Aikido Amplifier

This is th page that I remember reading before building the premp. Beware, it mentions genius, so read at your own risk.
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Old 22nd July 2021, 04:51 AM   #36
Chris Hornbeck is offline Chris Hornbeck  United States
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So they're to protect against catastrophic stupidity. Happens, I guess.


John Dee was an alchemist (but so was Newton) who saw the way forward into science, at a time when people still believed in witches. We're now living in a time when science, or even clear thought, is devalued. Foolish, foolish humans.


All good fortune,
Chris
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