AC voltage probe (CB8185E)

This circuit for voltages up to about 20 V was found in a 90s Popular Electronics. The LED can be of any type or color.

Audio expander (CB8507E)
Based on the Philips TDA3810N, this circuit was found in an 90s Electronics Now. The circuit has two...
Sound intensity indicator (CB23649E)
This simple circuit does not use active components and uses a small speaker as a microphone. The...
Car Power Amplifier (CB17259E)
This power amplifier configuration can be used in a public address system (ads) in the car. The...