This be Basic Dual DC Power Supply 6 volts (+6Vdc ground -6Vdc). Which used easily a little electronics components and so cheap. But they used for the circuit that use lower current than 50mA only. If more than this current makes high ripple or high noise.
We see in Figure 1 we will see that an AC 220V power reaches to a transformer to induce input AC voltage 220V to 6V. then it into both diode to half wave rectifier until gets positive (D1) and negative (D2), next both capacitors C1,C2 are used for smooth a flactuating current into the stable voltage at output about +8.4Vdc and -8.4Vdc (when low current load.)
These circuits may be necessary for you.
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