6D6 for analog logic

[Greg Hyatt]

I acquired several 6D6 tubes to play with analog logic. They provide an external connection for the third grid for variable mu. Unfortunately all of the circuit examples I can find are for IF amplification in AM radios. Can anyone steer me to simple resistance coupled amplifier examples, or better yet, data sheets like the ones which have spoiled me when using 12AX7 and other popular tubes?

 

[rayma]

data sheets like the ones which have spoiled me when using 12AX7 and other popular tubes?

http://www.nj7p.org/Tubes/PDFs/Frank/049-RCA_Cuningham/6D6.pdf
https://frank.pocnet.net/sheets/127/6/6D6.pdf
http://www.bunkerofdoom.com/tubes/syl43/DATA/1943/P88.GIF

 

[Greg Hyatt]

Thanks rayma, but I was trying to find more detail and examples. Most of the data sheets just state "tie to cathode" for G3. But I need to better understand its use to control mu. The last page of the Tung-sol data starts in that direction. Do you know of any variable-mu application examples?

 

[rayma]

Do you know of any variable-mu application examples?

It's hard to find examples at this point.

 

[Ketje]

The variable MU has nothing to do with the µ of triodes nor with the third grid. It is a variable transconductance ( µA/V , short MU ), used at RF frequencies to contole the gain, AGC. Those tubes are not very good for AF, the gain changes with the amplitude of the signal.
Mona

 

[Eli Duttman]

Greg,

Variable μ is achieved by varying the helix pitch of g1. Increase the negative bias sufficiently and the area of tightly wound grid does not allow electrons to pass.

 

[Greg Hyatt]

Yes, I have struggled to separate the influence of variable helix in G1 which provides a soft or remote cutoff (and the resulting variable mu causing the non-linear response to AF signals of high amplitude), and the ability to reduce gain with the supresor grid. I am more interested in the use of the supresor grid and do not intend to apply high amplitude signals to G1 or leverage remote cutoff.

 

[PRR]

What is "analog logic"?

"Logic" is usually ON/OFF operation. Put G3 at cathode, G1 and G2 control current; put G3 at -30V, no current flows to plate, a "gate" or "inhibit".

Fussing about the Mu makes me think you are doing multiplication, "operational computing", not Logic.

 

[Greg Hyatt]

You are correct, I am pursuing multiplication rather than binary logic.

 

[DF96]

You mean analogue computing?

 

[Greg Hyatt]

yes