Vacuum Tube Hearing Aids—General Information

Although Lee DeForest invented the triode vacuum  in 1906, it was not employed in hearing aids until 1921.

The first hearing aid using a vacuum tube was purported to have been made by Earl C. Hanson. He called his hearing aid the Vactuphone. It used one small peanut tube (below right) to amplify the output of a carbon hearing aid.

The Globe Hearing Aid Company and Western Electric collaborated to manufacture the Vactuphone.

By the early 1940s, Raytheon had developed miniature vacuum tubes. It was these miniature vacuum tubes that made body-worn hearing aids a reality.

These miniature vacuum tubes were only about 1¼” in length and about ⅜” in diameter. Although the component sizes of the day were still quite large, this made it possible to manufacture a hearing aid small enough to fit inside a shirt pocket.

Close-ups of two sub-miniature tubes used in hearing aids. The one on the left is the Raytheon CK533AX and the one on the right is the Raytheon CK512AX

The same two tubes (reversed positions) showing just how small they really were—only 1½" to 1¾" including their pins.

Unfortunately, the power requirements of these aids made it necessary to use two relatively large batteries—an "A" battery to power the filaments of the vacuum tubes and a "B" battery to supply the high-voltage for the plate current.

The batteries were worn external to the hearing aid itself and the name "Two-piece" hearing aid was used to describe them.

Until about 1945 "Two-piece" hearing aids were the norm. However, improved vacuum tube design reduced current requirements. As a result, battery manufacturers were able to reduce the size of the batteries used in hearing aids.

At the same time, electronic components were also being miniaturized. This allowed the hearing aid manufacturers to design hearing aids with internal batteries. After 1945, these "One-piece" hearing aids quickly replaced the more cumbersome "Two-piece" hearing aids.

• Large vacuum tube from early table model hearing aid (4½" high)
• Peanut Tube from Vactuphone hearing aid
• Miniature radio tube from 1940s
• Two sub-miniature Raytheon hearing aid vacuum tubes
• Transistor
• Integrated circuit (⅜")

With continuing improvements in both batteries and components, hearing aids continued to reduce in size until 1953 when the vacuum tube was suddenly supplanted by the transistor.