Simple question from a tyro.
Why do some valves have more than one pin for a connection.
For example:-
I'm going to use 6C45pi in cascode for my RIAA phono first stage.
They have 3 pins connected to the cathode and 2 pins connected to the grid.
Why?
As Cag is important here and I only really need one pin, what do I do with the other pins?
Sorry if this sounds dumb to experienced members, I've searched the web but didn't find an answer.
Why do some valves have more than one pin for a connection.
For example:-
I'm going to use 6C45pi in cascode for my RIAA phono first stage.
They have 3 pins connected to the cathode and 2 pins connected to the grid.
Why?
As Cag is important here and I only really need one pin, what do I do with the other pins?
Sorry if this sounds dumb to experienced members, I've searched the web but didn't find an answer.
Valves designed for use at HF and UHF have electrodes going to more than one pin in order that, no matter what the layout, short wires can be used to each electrode. At UHF, a short bit of wire is an inductor. I've never worried about unused pins, although some people suggest that a grid-stopper resistor to each grid pin, and then connected together at the far end, allows a smaller total value of grid-stopper, reducing noise.
Multiple grid stoppers, arranged in a "cone", are in order when using a 5842 in common cathode circuits. The 5842 was intended for use as a grounded grid high RF amp and the multiple grid connections help control unwanted reactive effects. With its high gm, the 5842 will oscillate without stoppers "everywhere".
IMO, it pays to look at the duty any type was originally intended for, as much can be learned. Many of the small signal types used in HIFI audio circuits were originally intended to be used in RF circuits. The EF86 pentode is 1 of the few small signal types developed (Mullard) for HIFI service.
IMO, it pays to look at the duty any type was originally intended for, as much can be learned. Many of the small signal types used in HIFI audio circuits were originally intended to be used in RF circuits. The EF86 pentode is 1 of the few small signal types developed (Mullard) for HIFI service.
Basing diagram is..erm... I don't remember what it is. 
Whatever NC or IC pins. I mean the wires go to the button base inside but aren't led out to the phenolic base, though you can't see because 1. all the pins are there and 2. it's notoriously difficult to see the actual bonding between base pins and where they pass through the glass.
Tim
Whatever NC or IC pins. I mean the wires go to the button base inside but aren't led out to the phenolic base, though you can't see because 1. all the pins are there and 2. it's notoriously difficult to see the actual bonding between base pins and where they pass through the glass. Tim
Wow!, many thanks for all the replies.
It seems I didn't ask a daft question after all
OK, so grid stoppers are a good idea, and I agree.
So the followup question is:
as the 6C45pi will be used for *audio* duties, is there any reason to just not join cathode pins together, and more importantly, join the grid pins together and use a single grid stopper?
The R term is way bigger than C or L for parasitic oscillations, so joining grid pins to a common stopper should suffice ?
Just testing the waters here
It seems I didn't ask a daft question after all
OK, so grid stoppers are a good idea, and I agree.
So the followup question is:
as the 6C45pi will be used for *audio* duties, is there any reason to just not join cathode pins together, and more importantly, join the grid pins together and use a single grid stopper?
The R term is way bigger than C or L for parasitic oscillations, so joining grid pins to a common stopper should suffice ?
Just testing the waters here
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