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.

The Sonic MA1 amplifier.  Tube compliment is a 12AX7 preamp and a 50L6 power stage.  Undistorted power is about 3 watts.  This amplifier is built for 120v mains only.  It is not possible to set up for 240v in its current design.

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Under chassis view of the Sonic MA1. 

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Rear view of the Sonic MA1.

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The Sonic MA1 Schematic.

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