Paralleling Triodes in a 6SN7GT

rebos123 · 21st January 2009, 01:20 PM

Hello,
I am sure this is a newbie question but I am just getting my feet we in tube circuit building.
I am building a preamp circuit using a 6sn7gt. I have it configured as an anode follower, with an Ra = 20Kohm and Rk = 500ohms. I have a 250Kohm grid resistor.
My question is, if I tie both triodes together inside the tube (pin1 to 4, 2 to 5, 3 to 6) does this throw the calculations off for Ra and Rk? Should I double their values to have it work correctly? Thanks for any help.

dsavitsk · 21st January 2009, 03:51 PM

rp is halved, Gm doubles, current doubles. If you look at the plate curves, double the current numbers on the LHS to make your calculations.

The grid leak stays the same, the load (for the same line) can be halved, and the cathode resistor, for the same bias, can be cut in half.

rebos123 · 21st January 2009, 04:58 PM

thanks - I was not sure about the load resistance either. It seemed like a shame to let the other triode in the tube just sit there unused!

21st January 2009, 01:20 PM	#1
rebos123 diyAudio Member Join Date: Jan 2006 Location: Cleveland, OH	Paralleling Triodes in a 6SN7GT Hello, I am sure this is a newbie question but I am just getting my feet we in tube circuit building. I am building a preamp circuit using a 6sn7gt. I have it configured as an anode follower, with an Ra = 20Kohm and Rk = 500ohms. I have a 250Kohm grid resistor. My question is, if I tie both triodes together inside the tube (pin1 to 4, 2 to 5, 3 to 6) does this throw the calculations off for Ra and Rk? Should I double their values to have it work correctly? Thanks for any help.

21st January 2009, 03:51 PM	#2
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	rp is halved, Gm doubles, current doubles. If you look at the plate curves, double the current numbers on the LHS to make your calculations. The grid leak stays the same, the load (for the same line) can be halved, and the cathode resistor, for the same bias, can be cut in half. __________________ http://www.ecpaudio.com :: http://diy.ecpaudio.com

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21st January 2009, 04:58 PM	#3
rebos123 diyAudio Member Join Date: Jan 2006 Location: Cleveland, OH	thanks - I was not sure about the load resistance either. It seemed like a shame to let the other triode in the tube just sit there unused!