Previous posts have talked about early vacuum tube and transistor hearing aids, and the hearing aid batteries they used. A tremendous change occurred in hearing aid size in going from vacuum tubes to transistors as amplifiers. Much of that related to changes in the battery size as well, as previously discussed.
This post is intended to show how some of these batteries actually looked as attached and/or inserted into hearing aids, and how these changes occurred over time, especially during the late 1940s and into the 1950s.
Battery Supply for Vacuum Tube Hearing Aids (1942 Product)
These are generally the images shown in any discussion about the history of hearing aids. This post will not overdo this, but instead show how these power supplies operated with one of the author’s old boxed-up hearing aid collection units.
The Zenith A2A was an early two-part hearing aid (Figure 1). Part one consisted of the hearing aid, and part two consisted of the two large batteries required to operate the hearing aid. The batteries were often contained in the same pack (pack shown in the right image in Figure 1 and shown in intended use in Figure 2.
Battery Supply for Vacuum Tube Hearing Aids (1946 Product)
By 1946, both the vacuum tubes and batteries had been reduced in size, as shown in Figure 3 and were housed in the same package (minus the receiver). This included both the “A” and “B” batteries.
Beltone Harmony (1946)
The Beltone Harmony hearing aid shown in Figure 3 is such a monopac. This vacuum tube hearing aid contained a RM-4 “A” battery and an Eveready 413E “B” battery in the same case as the remainder of the electronics.
Battery Supply for Vacuum Tube Hearing Aids (1947 Product)
By 1947, body-worn hearing aids had made continued improvements in vacuum tube size and lower battery power requirements.
Acousticon A 90M (1947)
Figure 4 shows the Acousticon A 90M body-worn hearing aid. This hearing aid still used the 1.5-volt RM-4 “A” battery, but the “B” battery voltage had dropped to 15 volts. This hearing aid was slightly smaller in size than the Beltone Harmony of just one year earlier, showing that even small changes in size was a design goal.
Battery Supply for Vacuum Tube Hearing Aids (1950 Product)
Microtone T-10 or Microtone “Ten” (1950)
This was a rechargeable hearing aid using 3 vacuum tubes. It was powered by a RM-1 “A” battery and a 504 “B” battery (Figure 5). It was identified also as “Sealed Power.” This hearing aid had a Sterling Silver case and came with a dresser top storage case that had a battery tester called the “Micro-Mizer.”
Battery Supply for Vacuum Tube Hearing Aids (1951 Product)
Continued size reduction, but with increased power was a design feature in the early 1950s.
Zenith Super Royal (1951)
A good example is the Zenith Super Royal in 1951 (Figure 6). This was one of the last vacuum tube hearing aids (3 vacuum tubes) made by Zenith, changing to transistorized hearing aids in 1953. This unit was unique in that it used four batteries: two 1.5 volt “A” batteries (Zenith size 222, same size as RM-1), and two 15-volt “B” batteries. Only one of the “A” batteries was in use at any given time, with the user periodically switching between the two “A” batteries (switch on the top of the aid – A1-A2) to provide some recovery while the other was being used. The “B” batteries (22.5 V) were connected in series to produce 45 volts for increased output power.
The next post will describe some battery products for early transistor hearing aids.
Fascinating history. I have worn aid since 1970, now dissapointed with digital types, processing ONLY to reduce feedback ( Cant get decent ear molds anymore ), audio artefacts generated as coefficients update as device’adapts’.
World is full of warning ‘beeps’ thesedays ! . Hearing aid design is now based on Fashion viz unobtrusive etc and Limits SPL. Recently tried bone conduction Bluetooth headset – Quality great volume adequate but Bluetooth latency makes it useless for conversation – made up body worn style amp to drive bone conductor via cord and use lapel worn microphone- result is bliss. Question is,where can I buy one instead of using up my time ? NB I am profession (retired) electronics design eng.
I am inspired by your work and got some great ideas. Thanks and keep sharing 🙂