At a glance


  • Symmetrical power supply for audio devices
  • Voltage defined by 2 pairs of resistors
  • Small 5x5cm footprint
  • PCB available in our shop

This is a simple symmetrical power supply for devices like preamplifiers, phone stages or similar. The voltage regulator IC can provide up to 1A current, but I recommend to use it for <200mA. The voltage drop on the regulator should be a few volts, then you can use it without additional heat sinks.

Voltage is controlled by 2 pairs of resistors. The following values ensure, that the current flowing through the regulator is at least 5mA.

R1 are the 2 inner resistors, R2 the outer resistors.

Voltage R1 R2
5V 249R 750R
9V 249R 1.5k
12V 249R 2.1k
15V 249R 2.67k
18V 249R 3.24k

Maximum diameter for the electrolytic capacitors is 8mm.

The capacitors in front of the voltage regulator must be specified for at least 1.5 x the voltage of the transformer. To be on the safe side, you should use capacitors that are specified for 2 x the transformer output voltage. For the capacitors after the voltage regulators (the 4 capacitors near the ICs on the right side named C13-C16), maximum voltage needs to be at least the output voltage.


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