THE SONIC MA1
PROTOTYPE

The sonic MA1 is a 1950’s design utilizing a 12AX7 preamp and a 50L6 power stage.  Undistorted power output is about 3 watts. 

The power transformer in this amplifier is a 50VA 120-240 /120 isolation transformer.   The series heaters of the vacuum tubes require 62 volts.  The primary of the transformer is wired for 240 volts, and when connected to 120v mains, this gives us 60 volts at the secondary - ideal for the series heaters.  The 60 volts AC is then fed to a solid-state voltage doubler, delivering about 160 VDC after filtering.