If you need a dual power supply. But you only have a single supply source. So should build this power supply splitter circuit.
Dual DC Regulator using +12V, -12V and Ground output
Multi voltage power supply circuit. There is 2 Dual output, The 12V are +12V,-12V, Ground. And also the 5V are +5V, -5V, Ground. All 1A max.
This is a basic unregulated Dual DC 6V Power Supply circuit. The output includes +6VDC, Ground, and -6VDC terminal. In the circuit below we use easily a little electronics components and so cheap.