[Amps] 3-400Z vs. 4-400A

[Richard]

>[cut and paste]
>>> --------- Forwarded message ----------
>>> From: W0YR@aol.com
>>> Think about it.
>>> The Swan amps don't furnish ANYWHERE NEAR 
>>> 3,400 Volts B+.  Why even bother to point out the 
>>> bias requirements of a 4-400 operating in GG 
>>> with 3,400 volts  on the plate?   
>-
>Because other options are open season... One 
>might judge the value of a Dahl retrofit xfmr. Some 
>vintage Henry amps (with excessive filament and 
>Anode values) arrived with 3-400z's on board, an 
>SB-220 might be considered a candidate should 
>the owner have a supply of cheaper 4-400's when 
>the original tubes go away.  The original post 
>asked for information to compare the two tube 
>types... the posted reply was very useful, on topic 
>information. 
>-
>I've found the 4-400 a bit "stiff to drive" compared 
>to the 3-500z, but it's a nice tube to play with.  One 
>could easily apply a bit of screen voltage for lower 
>drive (and higher gain) applications. 

* More gain is obtained with DC screen V applied only if the RF driving 
signal is applied between the control grid and the screen grid.  With 
both grids at RF-ground and the cathode driven, this does not happen.  
However, with the grid being driven, more gain is available provided that 
the DC screen potential is high enough.  

>grid could be grounded (bias applied in the fil xfmr 
>ct) or dc floated (I don't prefer floating control grids 
>if a choice is available). But then you get away from 
>the simplicity of zero bias operation. 

* good point

>
>Adding tetrode operation to a swan amplifier is 
>also not out of the question. There's lots of space
>inside....

* Which would also solve the problem of no tuned input.

>One or two classic ARRL type 4-400 Handbook 
>projects come to mind with lower anode G-G 
>AB2 operation. 
>-
>>> Unless, of course one wants to point out his 
>>> library skills.  
>- 
>Pretty rude of you to attack Rich's about his 
>post offering valid information. The posted 
>information was on topic..  provide your on topic 
>information and get off your bitter horse ride. 
>-
>>> In case you DO want to up the Swan Amp's 
>>> plate voltage to 3,400 volts in order to 
>>> obtain the requisite idling current, there are 
>>> any number of authorities on the subject, 
>>> RIGHT HERE?  Just ask!
>-
>If the answer is on topic, why not post it 
>instead of playing personal attack 101 and 
>stingy with your info.... buck'o. 
>- 
>One is not limited to the mentioned 3400 volt 
>potentials as a min value to "obtain the requisite 
>idling current," there are any number of amps 
>members willing to offer up various options 
>and opinions without the additional cannon 
>fodder (personal attacks) attached. 
>- 
>The 4-400 is a tetrode and some very 
>innovative things can be done with that 
>old swan amp.  Just ask.... right here!
>- 
>cheers
>skipp
>
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-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
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