While looking around at the web page
http://www.geocities.co.jp/Technopolis/1660/5zl-372.htm
I noticed a fair amount of their AA5s had earphone jacks
that could be plugged into a jack wired between the 12AV6
and the output tube (30A5 or 35C5). See diagram at the bottom of
this page. With the jack ground
tied to the powerline! They use 100VAC, but that's not
that different from 120VAC. Seems they didn't worry about
shock hazards back then.