Microphone mixer (CB7988E)

This traditional mixer configuration with a high input impedance was found in a 90’s Popular Electronics. The JFET in the input admits equivalent.

Class A Amplifier - 2N3055 (CB1001E)
I found this circuit in an article in a 2003 publication. The circuit is an example of how to...
LM386 9 V Amplifier (CB25299E)
This 9 V amplifier has a gain of 20 and provides a power of a few hundred milliwatts. The circuit is...
Digital volume indicator (CB7008E)
Found in an old Elektor, this circuit uses two 7-segment displays to indicate the volume of an...