Class A Push Pull with 6L6GC

[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?

thanks
d1

 

[astouffer]

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/Amp_Design/Williamson 1952 The Williamson Amplifier.pdf

 

[d1camero]

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]

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]

Re: Re: Class A Push Pull with 6L6GC

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]

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]

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]

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]

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]

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.