How to Wire Unused Triodes

[Thisismyname]

Building an amp that has 3 gain stages, not sure how to wire up that 4th, unused triode.

I've seen amps that connect the unused triode to the one being used with jumper wires, but I've also seen amps where that unused triode isn't connected to anything.

Which is better?

[pdf64]

It’s fine to leave a triode section not used.
Unless the heater supply is 12V, it’s probably better to leave its heater disconnected. 
It may be best practice to connect the anode, grid and cathode to 0V circuit common.

If connecting triode sections in parallel, it may be better to recalculate the loadline, as a valve type with double the gm and half the anode resistance is created.

[Esquirefreak]

I've recently started using heptodes (7 pin) in a couple of builds, partly because of some circuits using 3 triodes. And also because they are dirt cheap. A 6AV6 tube is a single triode equal to a 12AX7/ECC83 and cost only way less (for a good quality tube).

Might be worth considering :)

/Max

[thetragichero]

i'm all about using different tubes but it depends on the goal of an amp. if it's meant for someone to gig it's good practice to try to stick to valves that can be obtained in a strange town on a sunday. less fun but certainly pragmatic

[scstill]

I've recently started using heptodes (7 pin) in a couple of builds, partly because of some circuits using 3 triodes. And also because they are dirt cheap. A 6AV6 tube is a single triode equal to a 12AX7/ECC83 and cost only way less (for a good quality tube).

in the 6AV6 application do you ground the unused diode plates?

[sluckey]

Just ignore them.

     http://sluckeyamps.com/harvard/harvard_5f10_schem.pdf