The All American Four derives its name from the radio receivers manufactured from the 1940s through the 1960s.  These radios typically were all of similar design regardless of the manufacturer.  The receivers became know as “The All American Five” because all the radios were not only born and manufactured in America, but they also all used five tubes.  Manufactured by the millions, they all had a similar tube compliment: 

The heater strings in these receivers were wired in series.  Their individual heater voltages added up to 121 volts.  To save cost, these radios were also manufactured without a power or isolation transformer.

This amplifier uses two 12AV6 or 12AT6 tubes in the preamp, a 50C5 for the audio power output, and a 35W4 for the rectifier.  It has an undistorted audio output of about 3 watts.  An isolation transformer is also used, ensuring safety.