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Old 10th October 2010, 01:10 AM   #1
athos56 is offline athos56  United States
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Default 6B4G PPP idea

I got bored today and tried to come up with a 6B4G PPP amp. This is really rough so take it easy on a design newbie. The phase splitter is an input transformer, the main gain stage is 2 pentodes (6SJ7 or EF86, because thats what I have), the drivers could be any number of things 6SN7s or these 1626s I got. I'm mainly unsure about the negative supply for the drivers and the output tubes. I was hoping to run them both off of one supply and have some balance adjustment for the output tubes. So here it is, it will at least give you an idea of what I'm thinking of, even if its rubbish.

Athos
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Old 10th October 2010, 02:26 AM   #2
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Or maybe something along the e-linear lines? I added another pot to the bias scheme. Thanks!
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Old 10th October 2010, 08:32 AM   #3
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Ok Last one, warmer colder?
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Old 11th October 2010, 06:55 AM   #4
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Default Last one

Even though 'm not getting any traction on this thread, I'll post what I fiddled with today. I lifted the frontend from the new Millett amp, and gave the CFs CCSs so that, "I think," I can keep the whole thing balanced. Rubbish?

Athos

PS, I think I could run the CF's CCSs off on the negative supply I use for the Bias and the input.
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Last edited by athos56; 11th October 2010 at 06:58 AM.
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Old 11th October 2010, 07:35 AM   #5
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Move the coupling caps from between two drivers to between the second and the output tube. You will need a negative supply. This will be the way to let the amp work in A2 where grid current is drawn.

Also I wouldnīt go for 6SJ7 or other low Gm tubes. Instead a good triode with mu 40-60 and no GFB. Maybe a triode-strapped 6SJ7 will do, but I havenīt got a clue.
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Old 11th October 2010, 08:22 AM   #6
athos56 is offline athos56  United States
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Thanks for the look, the last effort I posted has some of those changes. I will look at changing the input, I'm not set on the pentodes, I just have a load of them I got for cheap

Athos
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Old 11th October 2010, 09:21 AM   #7
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The actual desagn should be DPPP - Double Paralleled Push-Pull

6B4G has two paralleled triodes per se

More paralleled triodes - less focus in detail
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Old 11th October 2010, 10:36 AM   #8
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In your "Last one" you need to bias your CF's not to gnd but like you did in your previous schem.
Or you follow Revintages advice and move the caps. Then you need to use fixed bias for your CF's.

/Olof
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Old 11th October 2010, 04:53 PM   #9
athos56 is offline athos56  United States
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Ok the caps are between the CF and the output tubes, and the driver's CCSs share the negative supply. I think that a single -50 to -60 negative supply can be used for the input, drivers and the output tube bias. Thanks for the input!

Athos
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Last edited by athos56; 11th October 2010 at 04:57 PM.
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Old 11th October 2010, 09:24 PM   #10
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Quote:
Move the coupling caps from between two drivers to between the second and the output tube. You will need a negative supply. This will be the way to let the amp work in A2 where grid current is drawn.
Sorry, didnīt check my writing before posting. I ment the other way around. Off course the text should read:

"Move the coupling caps to between two drivers from between the second and the output tube"
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