pin count question

[gary h]

Hi all,

forgive my ignorance, but what is the difference between octal and 9-pin tube types? I'm not looking for a discussion on the sonic merits of each but just the simple facts.

Thanks,

gary

[SHiFTY]

What kind of difference? Octals are physically larger and more rugged, easier to solder up, the pins connect better with the sockets, they are better for heat dissipation and can generally handle higher voltages and wattages.

9-pins are compact, look cooler and generally are more modern in their design - compare an EL84 with a 6V6 for example- the EL84 is a better valve.

In my experience there are too many other variables to say for example that an octal preamp will sound better than a 9-pin preamp. The right valve in a well designed circuit will sound good.

[Tweeker]

With small signal stuff, some noval tubes designs focus on gain at perhaps the sacrifice of other qualities as feedback saw more use than when the octals were developed.

Noval tubes have lower lead inductance than octal tubes. More an issue at RF.

Higher gm types (and just more types in general) are more available in the noval format.

[gary h]

That's what I was looking for, thanks.

What does that one extra/less pin account for?

gary

[Tweeker]

The extra pin does not necessarily account or attach (or is parallel attachment) to anything.

Sometimes its used connected to a screen (pin to ground) for an electrostatic shield between two tube sections, or with say a triode/pentode compound tube you might just need all those pins, or more (11 pin etc.)

[gary h]

Thanks for the replies.

gary

[Miles Prower]

Originally posted by gary h
What does that one extra/less pin account for?

That extra pin allows for such things as being able to make triode/pentode types like the 6KE8, to center tap heaters for 6.3V/12.6V operation, to place an electrostatic shield between sections of a dual triode.

[Merlinb]

Since there was pressure on manafacturers to miniaturise, it was a natural step to go from octal to the smaller noval, and then 7-pin, and even smaller in the latter half of the 20th century with the sub-miniature valves.
Having more pins allows more valves to be fitted into the same bottle. In Britian, radios were taxed based on how many bottles were inside, so miniaturisation was important here, while America continued to use mainly octals (they like things bigger there, so I hear!)