I have an audio circuit which is supplied by a voltage of 9V dc and 12V dc. These voltages are produced by means of a conventional transformer which transforms the mains 230V ac 50Hz to 15V ac 50Hz. After the transformer there is a rectifier (diode bridge and capacitor) followed by two regulators, one for the 9V dc and one for the 12V dc.
My problem is that the transformer produces a heavy magnetic field, which couples with my circuit producing a low hum. I am thinking about substituting the linear power supply with a switching one, thus avoiding the 50Hz magnetic field.
- Is there around on the market a switching power supply with the requested characteristics?
- Is it better to use a power supply giving directly the 9V dc and 12V dc, or is it possible to Step down the 230V ac to 15V ac (without using a Conventional transformer) and keep in place the rectifier and regulators?