[MrFixr55]

I think that the cabinet of the 39-116 is absolutely gorgeous as compared to the regular console cabinets of the day. There is one of these in the "office" of the William Vanderbilt mansion museum in Centerport, NY.

I have long been a fan of adding aux inputs to period radios for diagnostic purposes and also to enjoy the sound of these radios without dealing with the distortion of current AM stations, noise and the performance of my home AM transmitter. Adding phono jacks was often done "in period", probably within 10 years of buying the radio. I'm sure that period electronics magazines for the electronics hobbyist (and back in the day, there were many) had articles for adding phono inputs, as RCA and others sold standalone turntables and changers meant to be plugged in to the radio. These got really popular in the 40s and 50s. RCA made a kit, P/N 9824 in the late 1930s to early 1940s to add a phono input. Several black dial Zenith schematics included instructions for adding radio-phono switches. I even remember an article in Popular Electronics in the 1950s where someone added a jack to plug an 8" speaker into his portable TV for better, front protected sound.

The important thing is to not do a hack job.

The idea of converting a class AB power amp to class A was interesting. Maybe the person was a HiFi and classical music affectionate and purist. Class B was popular in the early 1930s due to the high output wattage and circuit simplicity, but distortion was rather high. However, back in the day, RCA considered a distortion of under 5% to be "undistorted"

Factory installed Phono (or TV or FM) inputs became popular in the 40s and 50s, and even earlier. MY GE S-22A (RCA R7A), RCA 5T7 and RCA 5BT and 6BT farm sets and other sets of the early 1930s had terminal boards on the back to wire an external phono. The switch was part of the phono. I have 3 RCA sets from 1940-1948, including a 14BT2 1.4V / 90V farm set, a 16T2 and an RCA 1R91 "Livingston" I have 2 GE clock radios with factory installed RCA plugs and a very unique way of switching from radio to phono. The volume control had a center tap on the resistor to ground. One leg had the radio, the other leg had the phono jack. The wiper connected to the grid of the 1st AF through a cap. Other radios, especially Emerson, had an RCA Jack with a contact that was a switch arm. When a plug was inserted, the radio input was switched out, similar to an earphone or headphone jack on transistor sets.