[AMPS] 572-B Input impedance??

[Rich Measures]

>
>> TU Rich!  I am also thinking about trying neutralization on the amp, 
>> Maybe using a piece of solid copper from a piece of house romex wire (abt
>> 14 or 12 gauge I guess?) and running it parallel to one of the tubes abt
>> 1/2 inch away??, then to the filament choke and wrap abt 4/5 turns around
>> it  in the same direction that the choke was wound then to ground??? 
>
>To neutralize the amp, the phase must be shifted 180 degrees. 
>That would require the winding oppose the choke winding.
>
€  I recommend reading what Eimac's  ''Care and Feeding of Power Grid 
Tubes'' says about neutralization of grounded-grid amplifiers.  

>........
>You also, since the amp is a monoband amp, might be able to 
>stabilize it by series tuning the grid. The way to set that up is to 
>excite the cathode with a few volts of RF, 

At what frequency, Tom?

>and measured the RF at 
>the anode with a sensitive detector. Adjust the grid series tuning 
>capacitor for minimum feedthrough.
>
...  makes some sense.  


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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