Mod to prevent cathode follower arcing on startup

[Chuck H]

I think this is Nick's initial post on the matter. I didn't look for follow ups.

https://music-electronics-forum.com/...thode+follower

[g1]

If you have a tube rectifier it may not be an issue.
nickb has done a lot of analysis on this but I can't find the thread right now. Helmholtz referenced it recently here: https://music-electronics-forum.com/...l=1#post549650

[mikepukmel]

Hi All,
Getting back to finish my work in progress JTM45 circuit build. Ive read, and also heard first hand from friends, that with the standard JTM45 circuit, the cathode follower has a tendency to arc. Some comments on various blogs say its due to the tube not yet conducting, but HV is placed on the tube, and the cathode follower has no plate resistor, so its plate is at higher voltage, the plate to heater voltage is too high and it arcs. Also, read some anecdotes that vintage tubes were less likely to arc, or at least self destruct due to construction.
Merlin's book has two suggestions, one is a neon bulb, the other is dc (elevated?) heaters with a diode. Has anyone had experience with either solution, or a different one? Id hate to roast the tube before I ever got sound out of the thing. Hopefully, there is a good reliable solution that doesn't make the amp character too different.

Thanks!
Sparky.


EDIT: I think what I wrote above is wrong. The cathode follower has DC on the grid. its grid to cathode, or grid to heater V. (Sorry)