Hi, does anyone know what the first radio to use a push pull output was? I need more trivia for my electronics class.

:Hi, does anyone know what the first radio to use a push pull output was? I need more trivia for my electronics class.

I know a 1929 RCA Radiola mod 80 had pp output. I was amazed to see that but I don't know if there was anything earlier. Nick

::Hi, does anyone know what the first radio to use a push pull output was? I need more trivia for my electronics class.
:
:I know a 1929 RCA Radiola mod 80 had pp output. I was amazed to see that but I don't know if there was anything earlier. Nick
The "Balanced Amplifier" was developed by Bell labs under the supervision of J. M. Carty in 1914. It's first commercial application was in repeter service on the trans continental telephone line of 1915. Push Pull output was used in the Western Electric 7-A amplifier, an audiop power amplifier developed in 1919 for sound reinforcement applications but used extensively as an aodio amp in early (CIRCA 1922) deluxe home receiving installations. The 1922 vintage Westinghouse Aeriola Grand (arguably the first self contained home receiver, with built in speaker and batteries) and the similar Radiola Grand (of 1923) also used this technology, as did the phenominally popular Radiola III-A of 1924. All of these sets used the cranky and underpowered WD-11 dry cell tubes, which would have had difficulty producing reasonable loudspeaker volume without the push-pull circuit. With the coming of the first real audio power tubes in 1925 (the storage battery UX-171, the dry cell UX-120, and the "super power" UX-210, the push pull circuit fell into temporary desuitude. The "super Power" 210 required 450 volts on its plate for an output of 1.5 watts. With the increaded use of electrodynamic loudspeakers in modest priced sets there grew a demand for a low priced aource of audio power. In late 1927 the Grigsby-Grunow-Hinds Co. introduced its Majestic line of receivers. They featured console cabinets, built in dynamic speakers, and Push Pull UX-171-A tubes which produced nearly 1.75 watts output with only 180 volts on the plate. The trend toward Push pull grew throughout 1928, becoming the industry standard for the 1929 season.