[Amps] Dual GS35b input impedance

[Tomm Aldridge]

Was planning on 3000VDC.  Thanks for the advice.

jeff millar wrote:
> I've seen a variety of values for GS-35 input impedance over the range 
> 25 to 100 Ohms.  It varies between tubes because the grid bias varies 
> with these russian tubes.  I tend to believe the input impedance runs 
> towards the low end of that range.  It runs lower than 8877 and the like 
> due to the high grid current.  Cathode drive impedance is proportional 
> to Eg / (Ip + Ig).
> 
> Definitely halve the impedance for two tubes in parallel.  It might well 
> end up 12-25 Ohms.  Running high plate voltage will increase bias and 
> increase input impedance.
> 
> jeff, wa1hco
> 
> Tomm Aldridge wrote:
> 
>> I am now at the stage of designing my tuned input for the dual GS35b 
>> amp that is in process here.  There seems to be a general concensus 
>> that the tube presents a 50 Ohm impedance when cathode driven in GG 
>> configuration.  Can I assume a 25 Ohm input impedance as a good 
>> starting point for my input filter design?
>>
>> Regards
>>
>> KD7QAE
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> 
>