Tube sockets

[Mgt280y]

Just wondering, im building a valve caster and recived my tube and s%^&*et does any one know what the hole in the middle of the socket is for as it has a solder lug on it.

And apologies if this is in the wrong place and feel free to remove if it is but

I am considering doing a run of tube cages in various materials brass bronze aluminium copper and wondered if anyone would be interested i will start with 3 ring style for 12au7 first as this is what i need but can machine any size really, just trying to gauge if is worth doing a load

[amptramp]

I assume you are using 9-pin miniature sockets since this is what 12A*7 tubes use.  Many miniature sockets (both 7-pin and 9-pin) had a single solder terminal in the middle to facilitate grounding and to act as a shield to avoid crosstalk between pins.  Even if you are not using it, it should be grounded since a floating (unconnected) terminal may pick up noise.

[vigilante397]

I definitely agree with amptramp (generally when tubes are involved it's safe to agree with him), if you plan on leaving it there definitely ground it.

On a couple builds I have removed the terminal altogether and super glued an LED in its place to give the tube an unnatural (usually blue) glow

[PRR]

Grounding the center lug may be "essential" in VHF (TV frequency) work.

It is handy in point-to-point audio work when you have several small to-ground parts.

IMHO it should not be necessary to ground it in most audio, but hey, it couldn't hurt.

Note that nice ring tube-cages are readily available on eBay. Look at their finish and prices before you start your own.

[printer2]

There is no reason to ground the center lug, it is not connected to anything. It does not shield anything or is connected to any shields. As said, it was used as a point to tie to in old designs.

[merlinb]

just trying to gauge if is worth doing a load

Depends on the price! On eBay they are between £5 and £8. Brass would be a cool alternative to the standard chrome/gold/black, though...

[Mgt280y]

I like using real metal where i can i have a few designs on the go at the min so im going to use brass and copper for a couple, just making the jig for the lathe