[AMPS] one side of heater to ground...

[skipp isaham]

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While constructing 80 & 170Mhz triode amplifiers 
for a research project (some time back), I had 
reason to contact Bill Orr with questions. One of 
said questions was to ask why one must tie the 
heater and the cathode of the 3cx400a7 triode to 
one side of the heater.  From memory, this was 
suggested in a data sheet I had at the time. 
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Other than "smart practice," he wasn't able to give me a 
concrete reason. Memory of that moment has been in 
my noodle for some years.  
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I made the amplifiers (of which I still have right here) 
trying both the separate and tied heater - cathode 
combinations.  
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I used common Omite chokes and some home brew 
chokes in the circuits. Both amplifiers did their tasks 
and are now in standby storage.  
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I didn't notice much operational difference using 
the heater/cathode connection combinations.  Might 
be the power level I was working with, the type of 
tubes or I just got lucky.  So why is it a common 
must-do to tie a side of the heater and cathode as 
one in some types of tubes..?   There's a reason 
out there somewhere that I must have missed?
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skipp
-
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: Rich said:
> It is my opinion that the heater should always be connected 
>to the cathode and the heater should float -- unless one has a 
>freebee supply of new tubes.
: I agree with that sentiment - even if you have a supply of 
: free tubes!
: 73
: Peter G3RZP

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