Hearing aid amplifier (T1580E)

This circuit is from a 1947 Radio Electronics. The 4-tube circuit is battery powered and uses a crystal phone.

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Lamp or motor control (CB7222E)
This circuit can control the power from 0 to 70% of the maximum power on a load. The circuit was...
Headphone Amplifier (CB24080E)
This circuit is from a Radio Electronics from October 1970. The circuit uses transistors from that...
Baxandall with CA3140 (CB11981E)
This tone control was obtained from the CA3140 datasheet, originally created by RCA. The CA3140...