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Posted new P-P power amp design
Posted new P-P power amp design
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Old 5th September 2009, 11:32 PM   #1
pmillett is offline pmillett  United States
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Default Posted new P-P power amp design

Posted new P-P power amp design

Hello all & happy labor day -

I just posted the design of a new power amp that I've been working on for some time.

This is a push-pull amp pentode using sweep tubes. Not screen driven (sorry SY) but pentode mode, with plate-to-grid feedback. Using 6JN6 or 6JM6/6GV5 tubes it does about 18W. Works with no global feedback, or with 6dB of feedback.

Drivers are also pentodes. The amp is set up to cancel some distortion between the driver and output stages (yes, it really does work!)

My goal was a practical and affordable amp. The total BOM cost is about $325.

Details are here:



Last edited by pmillett; 5th September 2009 at 11:38 PM.
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Old 5th September 2009, 11:44 PM   #2
whitelabrat is offline whitelabrat  United States
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Happy day!
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Old 6th September 2009, 01:56 AM   #3
Tubelab_com is online now Tubelab_com  United States
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6GV5's are still listed on the dollar menu at ESRC, so for a buck, I would be tempted to dial up a bit more B+, OK a lot more B+ but that is just my MO. I got a bunch of these when they first went on the dollar menu. I think that I have several hundred 6CB6's and a bunch of other IF tubes with the same pinout. If I ever get some time, I might put one together.

The Edcor power transformer looks like a good choice for the Simple P-P, so I may get one of these.
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
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Old 6th September 2009, 11:35 AM   #4
bigwill is offline bigwill  United Kingdom
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Pentodes are SOOOOO in fashion right now
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Old 6th September 2009, 11:53 AM   #5
revintage is offline revintage
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Nice use of Compactrons and 7-pins.

Calculated the Zout of each output tube to ca 1k and Zin to ca 7k with inverse feedback applied.

This looks great!

Last edited by revintage; 6th September 2009 at 11:56 AM.
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Old 6th September 2009, 02:18 PM   #6
Yvesm is offline Yvesm  France
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Hi Pete,

No compactron this side of the ocean !

Who may disagree with such design ?
Pentodes LTP, local FB, stabilized G2, no UL ! I love it.

Just a question, did you try to balance the driver (or even the pwr stage) by adjusting screen voltage ?
This affects transconductance and seems to be a way to match tubes "dynamically".
Not yet checked, work in progress ....

CUSOON, I hope.

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Old 6th September 2009, 02:48 PM   #7
Mickeystan is offline Mickeystan  United States
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Great looking design and beautiful execution. I can tell by the design elements and the thoughtfull layout that your truly an engineer. Form clearly follows function and the use of these traditional TV tubes and the feedback scheme makes the design unique. Very cool. From one engineer to another, Job Well Done!

Doug S. (aka Mickeystan)
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Old 6th September 2009, 03:12 PM   #8
kmtang is offline kmtang  Canada
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Are those 12 pins tube sockets still available??

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Old 6th September 2009, 05:01 PM   #9
vinylkid58 is online now vinylkid58  Canada
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Originally Posted by kmtang View Post
Are those 12 pins tube sockets still available??
Search our favorite auction site and you'll find the ceramic pcb version.

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Old 6th September 2009, 11:33 PM   #10
SY is offline SY  United States
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Posted new P-P power amp design
Nice one, Pete, despite the lack of screen drive. Looks like you've got some new software to replace AudioTester- what is it?
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
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