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pmillett 5th September 2009 11:32 PM

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:


whitelabrat 5th September 2009 11:44 PM

Happy day!

Tubelab_com 6th September 2009 01:56 AM

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.

bigwill 6th September 2009 11:35 AM

Pentodes are SOOOOO in fashion right now :devily:

revintage 6th September 2009 11:53 AM

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!

Yvesm 6th September 2009 02:18 PM

Hi Pete,

No compactron this side of the ocean !

Who may disagree with such design ?
Pentodes LTP, local FB, stabilized G2, no :RIP: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.


Mickeystan 6th September 2009 02:48 PM


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)

kmtang 6th September 2009 03:12 PM

Are those 12 pins tube sockets still available??


vinylkid58 6th September 2009 05:01 PM


Originally Posted by kmtang (
Are those 12 pins tube sockets still available??

Search our favorite auction site and you'll find the ceramic pcb version.


SY 6th September 2009 11:33 PM

Nice one, Pete, despite the lack of screen drive.:D Looks like you've got some new software to replace AudioTester- what is it?

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