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d3a triode wiring

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Posted on December 1, 2016 at 10:25:31
genelex
Audiophile

Posts: 95
Joined: October 16, 2005
 When triode wiring the d3a how should pins 1 and 3 be handled to best prevent oscillation. I believe they are both connected to the cathode internally .
thanks

 

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RE: d3a triode wiring, posted on December 1, 2016 at 16:57:51
JKT
Audiophile

Posts: 613
Location: Midwest
Joined: November 26, 2002
 Morgan Jones 4th ed. shows G2 & G3 connected to the plate for triode use.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln

 

RE: d3a triode wiring, posted on December 1, 2016 at 17:48:41
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 I guess I don't understand the question.

Pins 1 and 3 are both connected to the cathode.

The cathode normally goes to ground (through a resistor it you are cathode biasing the tube).

No real chance of causing oscillation.

Just use whichever one you want and leave the other one alone.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: d3a triode wiring, posted on December 1, 2016 at 18:20:57
genelex
Audiophile

Posts: 95
Joined: October 16, 2005
 So its best to leave one of the cathode pins unconnected ?

 

RE: d3a triode wiring, posted on December 1, 2016 at 18:37:50
Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002
 I don't see why not.

It's already connected to the cathode and the cathode will be connected to ground (or the cathode resistor to ground).

It's not like a high gm tube with a grid connected to two pins.

A high gm tube with a grid connected to two pins, both pins need grid stop resistors or problems can happen.

I don't see how a tube with two cathode pins will cause problems.

Maybe someone else will chime in with more info.


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: d3a triode wiring, posted on December 1, 2016 at 21:49:30
shane.
Audiophile

Posts: 394
Location: S.A.
Joined: March 27, 2004
 It depends if you use capacitors to shunt the cathode to signal common at HF (recommended), in which case it gives flexibility of connection with respect to size/fit form and function.

I agree with the M.Jones reference about triode connection D3a with extra grids to plate and not to cathode.

I use D3a in low noise application - and it is a tricky tube.. but worth it.


Shane.

 

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