I'm making a PCB for an audio amplifier + power supply (circuit here).
The power supply voltage rails with my transformer end up being about +/- 37V, and I want to generate a 5V rail from this for powering some cooling fans on the same PCB. This is pushing the limits of a typical voltage regulator (e.g. the max. input of a L7805 is 35V).
I tried a DC/DC converter (a R-78C5.0-1.0) but this produces audible noise on a speaker at the amplifier output (I put 10 uF decoupling caps at the input and output). One thing I didn't try yet is the EMC filter suggested in the datasheet here.
I found "high-voltage regulators" (e.g. an LR8), but the max. output current is 30 mA, and my fans need about 100 mA.
Is there a better way for generating 5V from 37V without producing EMC that I can hear as noise on the amplifier?
UPDATE: I'm an idiot. It turns out the noise was coming from having some signal wires too close to the transformer. I rearranged everything and now I can use the DC/DC converter without producing any audible noise at the speakers.