These modifications do not require
any changing of sockets in the audio speech amplifier section. The 6AH6
is a plug-in replacement for the original 6AU6, first audio amplifier.
Although the driver tube now uses a 6C4,
which is a seven pin tube, the socket will need to be rewired, except for
the filaments. Be sure to compare the schematic above to the original schematic
because some components have been changed, others removed and others remain
After the mods have been made, adjust the
resting current of the modulators to 60 milliamps by adjusting the variable
tap of R13.
For proper audio equalization, use an unamplified
crystal microphone such as an Astatic D-104.