The accompanying article doesn’t say for sure, but I’m guessing the gentleman shown at the left made some serious extra income 75 years ago, thanks to the audio amplifier he built, based on plans in the November 1946 issue of Popular Mechanics.

The general-purpose amplifier put out 32 watts, and had enough power to drive four large speakers. It could be used in emergencies, or to provide music and public address for school groups or outdoor activities. It had two 6L6 tubes in push-pull configuration running class AB-1, and weighed in at only 22 pounds, with a plywood chassis.