This circuit was found in a 70s documentation. The transistor is from that time. L1 has 4 turns of wire 20 in the form of 3/32 inches and L1 has 10 turns of the same wire,
Found in old documentation, this circuit applies to almost any common operational amplifier or...
This circuit is used with low impedance microphones, such as small speakers, magnetic capsules of...
This filter can be used to eliminate hum in sound equipment. Operational amplifiers can be 741 and...