[AMRadio] Mike Cable Capacitance

[Donald Chester]

I use an outboard audio amp for my 75A-4 receiver with a system of adaptors 
that requires no modification to the receiver itself.  I  pull audio 
directly from the grid pin of the 12AT7 1st audio stage (with the tube 
removed).  This is a high impedance point, 470k if I recall correctly.  To 
avoid high frequency loss in the 5 ft. or so of shielded cable between the 
tube socket and amplifier, I built up a cathode follower stage to replace 
the 12AT7.  It is a plug-in module that plugs right into the 12AT7 socket, 
and gets its B+ from the screen grid pin of the 6AQ5, which was also removed 
to conserve drain on the power supply and reduce unneeded heat in the 
receiver.  I can remove the plug-in units and replace them with the original 
tubes, and the receiver will be completely stock once again.

-k4kyv

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