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

[skipp isaham]

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