Less than 10mV is not considered low noise. Linear power supply with simple LM317\/337 and LM78\/79 series. In parallel, but can not be directly in parallel, each output with schottky diode, and then together. Switch power supply, power frequency noise? The switching noise inside is much more than the power frequency noise, so solve the switching noise first. Ultra low noise is cheaper remember TL5209, but only the positive. If the protection of the power supply chip level before doing good, ultra low noise power supply chip, can directly use the benchmark power op-amp low noise transistor (MOS) build a linear regulator circuit, positive and negative pressure depends entirely on how much current transistor (MOS), most of choice, a 10 a to wear.