Remote cutoff pentode/triode tubes?

[Tobyk]

Hello, does anyone know if there are any Remote cutoff (vari-mu) pentode/triode tubes (half pentode, half triode)?
Or are all of them sharp cutoff?

[Stevem]

Does the filament voltage matter to you?

I suggest you get your hands on a reprint of the RCA tube book RC-30, there not hard to find, in fact AES has them.

[roberto]

Is the 6F7 ok for your purpose?
https://frank.pocnet.net/sheets/127/6/6F7.pdf

[Phil_S]

RC-30 (1975 ed.) is available for free d/l or Amazon has a reprint edition. D/L here:
https://www.google.com/url?sa=t&rct=j&q ... Jp49hfdffd

I suspect the easiest way to get a list is to d/l Duncan's TDSL and use the search feature. http://www.duncanamps.com/tdslpe/

AFAIK these are safe downloads, however, you should judge risk for yourself. For TDSL, I suggest sticking strictly with Duncan's antiquated web pages and not get sucked in by other posers who redistribute the software.

So, my curious mind wants to know, what is the difference between a remote cutoff and a sharp cutoff? And what do we call the usual pentodes like EL84, 6L6, etc.?

[roberto]

what is the difference between a remote cutoff and a sharp cutoff?

A remote cutoff is a tube where the negative voltage of the grid slowly goes into no conduction (cutoff), where the last small conduction takes alot of negative grid voltage to reach zero.
Sharp cutoff needs few volts to reach cutoff and are generally more linear.

[martin manning]

I ran across this cross reference the other day. Seems like it might be useful for searching out tubes for particular applications:

https://www.angelfire.com/electronic/fu ... guide.html

Sorry, the pentode-Triode tab has only one candidate for the remote cut-off pentode/triode the OP is after, and limited data for that.

[Tobyk]

Thanks guys! It looks like there are very few of them out there. I dig the sturdy 8- and 7-pin tubes and prefer them over miniature tubes. But top capped ones, like 6F7, feels a bit too ancient even for me.
They're from the early 30's after all. Thought it would be nice having it as a CF with added compression/squish control, plus the added asymmetry of the vari-mu. Oh, well..

EDIT: Using the RCA Manual you so kindly provided, I actually found two which at least are semi-remote: 6LM8 and 6MU8 – thanks!

[Tobyk]

For the record, I think I found the only 9-pin triode/remote cutoff tubes there is: 6U9/ECF201

EDIT: I see now it’s 10-pin!? Didn’t know there was such a thing..