This circuit was found in a 73 amateur radio magazine from the 90s. An LED extends the scale from 0 to 5 V to 10 to 15 V in this bargraph circuit. Other zener values can be used.
Found in old documentation, this circuit makes use of amplifiers of the time, uncommon today. Next...
Rumble is a low-frequency oscillation that occurs in turntables due to variations in motor speed....
This circuit was found in a Popular Electronics from the 90s. The circuit uses common components...