This transformer-rectifier-filter arrangement gives you multiple output voltages with a single transformer. This AC-DC converter can be your solution is you need two level of symmetric power supply. Here is the schematic diagram of the circuit:
U1 and -U1 uses a basic symmetric supply configuration, with a center-tapped transformer and full bridge rectifier for. U2 and -U2 uses a voltage double configuration. We can expect higher voltage for these voltages, but we’ll always get lower current rating for this boosted voltages. This kind of power supply should be sufficient to power some pre-amplifiers or small signal amplifier stages.