Stereo preamplifier (CB8510E)

Found in a 90s Popular Electronics, this circuit is based on a uA739, an unusual component today.

LED Binary Counter (CB4345E)
This circuit came out in an American magazine that no longer exists. It's the Electronic...
Bass and Treble Control (CB918E)
This circuit can be added to any audio amplifier design, consisting of a good tone control with an...
Second order high pass filter (CB7522E)
Using a 741 op amp with symmetrical source, this circuit was found in a 1982 documentation. The...