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Old 6th September 2009, 12:32 AM   #1
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Default Posted new P-P power amp design

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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; 6th September 2009 at 12:38 AM.
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Old 6th September 2009, 12:44 AM   #2
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Happy day!
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Old 6th September 2009, 02:56 AM   #3
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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, 12:35 PM   #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, 12:53 PM   #5
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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 12:56 PM.
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Old 6th September 2009, 03:18 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, 03:48 PM   #7
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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, 04:12 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, 06:01 PM   #9
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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 7th September 2009, 12:33 AM   #10
SY is offline SY  United States
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Nice one, Pete, despite the lack of screen drive. Looks like you've got some new software to replace AudioTester- what is it?
A philosopher is a blind man in a dark room looking for a black cat that isn't there. A theologian is the man who finds it. - Mencken
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