Hugh Hetherington Hearing Aid Museum
Hugh Hetherington Hearing Aid Museum

The Hearing Aid Museum

Hearing Aids of all types—Ear Trumpets, Carbon Hearing Aids, Vacuum Tube Hearing Aids, Transistor Hearing Aids, Body Hearing Aids, Eyeglass Hearing Aids and much more!

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Click on the "General Information" button (top button above) for an overview and general information on this category of hearing aid.

 

Vacuum Tube Hearing Aids: 1921-1953

Maico Model M "Precisioneer" Vacuum Tube Hearing Aid

The Maico Model M, also known as the "Precisioneer", was produced by Maico Electronics, Inc. of Minneapolis, MN in 1944. The name "Maico" was derived from the initials of the Medical Acoustic Instrument Company.

 This hearing aid was a two-piece body worn aid. It measured 4˝" x 2⅜" x ⅞" (11.5 x 6.1 x 2.4 cm) and weighed 6˝ oz (184 g) without the batteries. It was worn in a man's shirt pocket or carried in a purse by a lady.

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Top view of the Maico Model M "Precisioneer" vacuum tube hearing aid showing the combined volume/on-off control.
 

 

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Bottom view of the Maico Model M "Precisioneer" vacuum tube hearing aid showing the design on the bottom front of the aid and the 4-pin battery/receiver jack (bottom center).

 

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Close-up of the battery/receiver plug of the Maico Model M "Precisioneer" vacuum tube hearing aid. It plugged into the bottom of the aid.

Since it connected two batteries and the receiver to the hearing aid, obviously one pin was for the 1˝ volt positive "A" battery current, one pin was for the 33 volt positive "B" battery current, one pin was for the receiver plus signal and the final pin was a common ground.
 

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Rear view of the Maico Model M "Precisioneer" vacuum tube hearing aid showing the model and serial number (center) and the 4-hole "adjusting bar" (bottom center).

 

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Close-up of the bottom left corner of the Maico Model M "Precisioneer" vacuum tube hearing aid showing the 4-hole "adjusting bar". Only hole number 3 contains an adjusting screw. It seems likely that this was actually a four position filter. When a screw was screwed into one of the holes, it switched in one of the high or low pass filters, thus giving different sound characteristics.

 

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The picture at the right shows in inside view of the Maico Model M "Precisioneer". It used three vacuum tubes and had a single volume control.

 

 

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A close-up of the rear (interior) view of the microphone showing various patent numbers for the US, Great Britain and Canada, 1931-1941.

The crystal microphone was manufactured by the Brush Development Company.

 

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Close-up of the receiver and ear mold of the Maico Model M "Precisioneer" vacuum tube hearing aid.

This Brush Development Co. crystal type receiver was commonly used on many of the hearing aids of the early 1940s rather than the more usual dynamic receiver used later on.
 

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Close-up view of the Maico Model M "Precisioneer" vacuum tube hearing aid battery cable plugs. The two-pronged plug (left) plugged into the "A" battery and the 3-pronged plug (right) plugged into the "B" battery.

 

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Close-up of the "A" battery plug of the Maico Model M "Precisioneer" vacuum tube hearing aid. Since both the plug (right) and the larger adapter (left) had the same size pins, one wonders what the adapter was really for. It doesn't appear to be needed.

 

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The Maico Model M "Precisioneer" hooked up to its "A" (right) and "B" (left) batteries. The earphone is at the extreme right.

 


 

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