[Amps] Tetrodes in GG Configuration

[Ian White, G3SEK]

k7fm wrote:
>
>There are some very good reasons to run a tetrode in grounded grid. 
>Using the 4Cx1000A as an example, running it grid driven will result in 
>unacceptable distortion products.  To get acceptable levels you must 
>increase the inverse feedback.  Grounded grid inherently provides 
>feedback and will improve the distortion products by about 6 db. 
>Collins ran the 30S-1 with a 4CX-1000A in grounded grid, but also added 
>negative feedback. The result is an amplifier significantly cleaner 
>than the tube itself.
>
But don't forget that this amplifier used correct DC grid potentials, ie 
different for G1 and G2.

Whenever this discussion comes up, there is always uncertainty about 
exactly what is meant by "grounded".

Usually the questioner is meaning to ask: "Can I run a ceramic 
4CXwhatever with both grids connected direct to chassis, same as you 
would with a glass 4-something?" Or in other words: "Can I do it the 
easy way, without screen and grid bias supplies?"

The answer to that is No, for the reasons that Rich gave in the very 
first response.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek