Radioear Model A-28 Vacuum Tube Hearing Aid The Radioear model A-28 was a table-top model vacuum tube hearing aid that ran on house current. It was manufactured by E. A. Myers & Sons of Pittsburg, PA in 1930. This hearing aid was a "heavy beastie" weighing in at 8˝ lbs. It measured 9” wide by 6⅞" high by 4⅞" deep. |  | Click picture for larger view | | |  | | | |
| The double carbon transmitter (microphone) is located in an opening in the bottom front of the hearing aid (right). The knob at the left was the volume control/on-off switch. The knob can be set to any level between 10 and 100.
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| The Model 28-A used two large vacuum tubes—a 471-B and a 433 or equivalent. The vacuum tubes now in this hearing aid are a 171-A and a 33. |  | Click picture for larger view | | | |
| The inside back showing the position and type of the original tubes. The tube on the left was originally a De Forest Audicon 471-B or equivalent while the tube on the right was originally a De Forest Audicon 433 or equivalent. |  | Click picture for larger view | | | |
| The magnetic receiver (earpiece) and power cord were stored in a small compartment in the top front of the hearing aid.
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