Class A Push Pull with 6L6GC

d1camero · 3rd December 2007, 01:50 AM

Hey all, I want to design an amp (guitar amp) that uses 6L6GC in push pull, but runs class A. Cathode Bias.

I have scoured the books to try and find how to calc OT impedance, cathode current and plate voltage but not much luck. Can someone give me an idea of how to calc these values?

thanks
d1

astouffer · 3rd December 2007, 02:05 AM

Try looking up the classic Williamson amp. I think the article goes as far as showing how to wind the transformers.

http://www.clarisonus.com/Archives/A...0Amplifier.pdf

d1camero · 3rd December 2007, 04:05 AM

Interesting read, but does not discuss calculating load impedances for push-pull class a, nor calculating cathode current or plate voltage.

Any other suggestions?

Miles Prower · 3rd December 2007, 05:15 AM

Quote:

Originally posted by d1camero
Hey all, I want to design an amp (guitar amp) that uses 6L6GC in push pull, but runs class A. Cathode Bias.

I have scoured the books to try and find how to calc OT impedance, cathode current and plate voltage but not much luck. Can someone give me an idea of how to calc these values?

If you can't get this from the spec sheet (See: Frank's) then you'll have to use a loadline to determine the values for Q-Point and load. I did a mini-tutorial on that Here

aletheian · 3rd December 2007, 12:31 PM

Quote:

Originally posted by Miles Prower

If you can't get this from the spec sheet (See: Frank's) then you'll have to use a loadline to determine the values for Q-Point and load. I did a mini-tutorial on that Here

HEY!!! Frank's is back up!! I yanked it from my bookmarks a few months ago because i thought it was a gonner. You just made my day.

6f6 · 4th December 2007, 12:58 AM

I you want to learn how to create a loadline, determine impedance, and determine distortion for an amp, go to Steve Bench's site.

Bandersnatch · 4th December 2007, 01:02 AM

hey-Hey!!!,
For Class A PP, just take the SE/single tube operating point, and double the load. Say fora 2k5 SE, go to 5k. In Class A, each side sees half the plate-to-plate load.
cheers,
Douglas

aletheian · 4th December 2007, 02:04 AM

Quote:

Originally posted by Bandersnatch
hey-Hey!!!,
For Class A PP, just take the SE/single tube operating point, and double the load. Say fora 2k5 SE, go to 5k. In Class A, each side sees half the plate-to-plate load.
cheers,
Douglas

Very true. D1camero, if you want to go that route, RCA's sheets and test data pages have operating points and very detailed info for A1 SE pentode mode in both fixed and cathode bias between 200v and 350v, and a little additional chart for A1 PP pentode mode at a few more op-points... should be close enough to whatever you need.

d1camero · 4th December 2007, 01:08 PM

Hey all, thanks for the help. I looked at Steve's site and others. FWIW Here is one that nicely walked me through the process:

http://www.freewebs.com/valvewizard

aletheian · 4th December 2007, 08:35 PM

Quote:

Originally posted by d1camero
Hey all, thanks for the help. I looked at Steve's site and others. FWIW Here is one that nicely walked me through the process:

http://www.freewebs.com/valvewizard

A friend of mine runs that site. He is a good guy, and I think he has a few more how-to articles planned for the site, so bookmark it.

3rd December 2007, 01:50 AM	#1
d1camero diyAudio Member Join Date: Nov 2006	Class A Push Pull with 6L6GC Hey all, I want to design an amp (guitar amp) that uses 6L6GC in push pull, but runs class A. Cathode Bias. I have scoured the books to try and find how to calc OT impedance, cathode current and plate voltage but not much luck. Can someone give me an idea of how to calc these values? thanks d1

4th December 2007, 01:02 AM	#7
Bandersnatch diyAudio Member Join Date: Jul 2003 Location: Ann Arbor, MI	hey-Hey!!!, For Class A PP, just take the SE/single tube operating point, and double the load. Say fora 2k5 SE, go to 5k. In Class A, each side sees half the plate-to-plate load. cheers, Douglas __________________ the Tnuctipun will return

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
2A3s in push pull; class A	Sir Trefor	Tubes / Valves	44	31st May 2013 03:37 AM
40W class A push pull amp with JJ 2A3-40w possible?	3nity	Tubes / Valves	18	26th May 2010 11:05 PM
Class A push-pull	Nikolas Ojala	Pass Labs	5	24th August 2009 12:58 PM
Class A, push pull amp using transistor	space2000	Solid State	18	7th August 2008 02:53 PM
EL34 Push Pull in Class A	arnoldc	Tubes / Valves	29	17th May 2006 11:52 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

3rd December 2007, 02:05 AM	#2
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	Try looking up the classic Williamson amp. I think the article goes as far as showing how to wind the transformers. http://www.clarisonus.com/Archives/A...0Amplifier.pdf

3rd December 2007, 04:05 AM	#3
d1camero diyAudio Member Join Date: Nov 2006	Interesting read, but does not discuss calculating load impedances for push-pull class a, nor calculating cathode current or plate voltage. Any other suggestions?

4th December 2007, 12:58 AM	#6
6f6 diyAudio Member Join Date: Oct 2006	I you want to learn how to create a loadline, determine impedance, and determine distortion for an amp, go to Steve Bench's site.

4th December 2007, 01:08 PM	#9
d1camero diyAudio Member Join Date: Nov 2006	Hey all, thanks for the help. I looked at Steve's site and others. FWIW Here is one that nicely walked me through the process: http://www.freewebs.com/valvewizard