Rumble filter (CB6541E)

This turntable filter was found on an 80's Elektor. The circuit makes use of operational features that are easily obtainable today.

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0 to 20 V x 2A power supply (CB19215E)
This variable power supply circuit was found in a German publication from the 1980s. The circuit is...
Metronome using operational (CB22060E)
We found this circuit in an English publication. The transistor can be BC549, and the power supply...
Low Voltage Flasher (CB6250E)
This circuit was found in Motorola documentation from the 1980s. PUTs are not common components...