[Heathkit] Question about tubes

[Kenneth G. Gordon]

On 14 Jul 2007 at 14:59, Tony Brock-Fisher wrote:

> The letters are just sequentially assigned. The last number usually
> identifies the number of elements, including the filament.

Yes. For instance: 6C4: 6 volt filament, third troide assigned a number 
in that list, 4 elements (filament, cathode, grid and plate).

However, like the English language, there are exceptions.

For instance, the 6K7 and the 6SK7 started out being the same tube, 
except that the 6SK7 was "single-ended", indicated by the "S". I.e, all 
connections were to the base, whereas the 6K7 had one grid connected 
to top cap. I.e., it was "double-ended".

Later, their characteristics became somewhat different.

Ken Gordon W7EKB