GU29 PP Amplifier

Tesla88 · 27th February 2013, 09:00 AM

Hi guys , a friend gave me some GU29 tubes , so i want to make a stereo amp with them.
I've a pair output transformers from "Geloso" amplifiers , designed for EL34 in Push Pull , can I use them for gu29 in push pull ? B+ at 400Vdc

What is the ideal Raa for GU29? 5k ?

Can you suggest a good sounding tested schematic? Audioromy ?

Thanks

SVStube · 27th February 2013, 10:03 AM

http://lynxaudio.narod.ru/articles/Lynx_VTA39.pdf

TonyTecson · 27th February 2013, 10:09 AM

nice sounding tube, i had a chance to repair an Audioromy....it can still be optimized...

5k push-pull will work, the problem with this tube is idle current bias matching on the plates, this you have to watch out for....o got red plate on one side of a new tube....

TonyTecson · 27th February 2013, 10:18 AM

Quote:

Originally Posted by SVStube

http://lynxaudio.narod.ru/articles/Lynx_VTA39.pdf

thanks for the link, if i were to build this amp, i would put 10 ohm resistor in series with each plate so i can check plate current balance....

the_manta · 27th February 2013, 10:35 AM

Raa depends on Ua and Ia.....
Hope you have a big stash to find a few with matching systems (especially in gm, static match can be adjusted via bias voltage)

Shoog · 27th February 2013, 04:45 PM

Can I suggest you look at my DC7 Mk3 thread to see a way of biasing up a shared cathode output tube. Its self adjusting and stable if the input valve stays reasonably well matched.

Shoog

TonyTecson · 27th February 2013, 09:43 PM

Quote:

Originally Posted by Shoog

Can I suggest you look at my DC7 Mk3 thread to see a way of biasing up a shared cathode output tube. Its self adjusting and stable if the input valve stays reasonably well matched.

Shoog

links please...

aardvarkash10 · 27th February 2013, 10:19 PM

http://www.diyaudio.com/forums/tubes...hlight=DC7+Mk3

TonyTecson · 27th February 2013, 10:22 PM

thanks...

Shoog · 28th February 2013, 03:28 PM

Quote:

Originally Posted by Tony

thanks...

This method can be very techy to set up in the first place - not for the faint hearted. I made a small adjustment to the output screens last night and got red plates on one of the PL84's.

Shoog

27th February 2013, 09:00 AM	#1
Tesla88 diyAudio Member Join Date: Dec 2011 Location: Italy	GU29 PP Amplifier Hi guys , a friend gave me some GU29 tubes , so i want to make a stereo amp with them. I've a pair output transformers from "Geloso" amplifiers , designed for EL34 in Push Pull , can I use them for gu29 in push pull ? B+ at 400Vdc What is the ideal Raa for GU29? 5k ? Can you suggest a good sounding tested schematic? Audioromy ? Thanks

27th February 2013, 10:09 AM	#3
TonyTecson diyAudio Moderator Join Date: May 2003 Location: Palatiw, Pasig City	nice sounding tube, i had a chance to repair an Audioromy....it can still be optimized... 5k push-pull will work, the problem with this tube is idle current bias matching on the plates, this you have to watch out for....o got red plate on one side of a new tube.... __________________ planet10 needs your help: Let's help Ruth and Dave...http://www.diyaudio.com/forums/plane...ml#post5010547[B

27th February 2013, 10:35 AM	#5
the_manta diyAudio Member Join Date: Nov 2006 Location: Munich, Bavaria	Raa depends on Ua and Ia..... Hope you have a big stash to find a few with matching systems (especially in gm, static match can be adjusted via bias voltage) __________________ Терпенье и труд все перетрут

27th February 2013, 10:19 PM	#8
aardvarkash10 diyAudio Member Join Date: Mar 2007 Location: Auckland, NZ	http://www.diyaudio.com/forums/tubes...hlight=DC7+Mk3 __________________ "It may not be easy for some to not hear differences, even if they are not there." - Vacuphile,

27th February 2013, 10:22 PM	#9
TonyTecson diyAudio Moderator Join Date: May 2003 Location: Palatiw, Pasig City	thanks... __________________ planet10 needs your help: Let's help Ruth and Dave...http://www.diyaudio.com/forums/plane...ml#post5010547[B


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27th February 2013, 10:03 AM	#2
SVStube diyAudio Member Join Date: Jan 2011 Location: Vinnytsya	http://lynxaudio.narod.ru/articles/Lynx_VTA39.pdf

27th February 2013, 04:45 PM	#6
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	Can I suggest you look at my DC7 Mk3 thread to see a way of biasing up a shared cathode output tube. Its self adjusting and stable if the input valve stays reasonably well matched. Shoog

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