It's done :) My switching DC-to-DC PSU.
I've been working on this design on and off since October 2007. Several prototypes later, and many $$$, I'm happy with it. All output voltages are regulated and adjustable via multiturn trimmers, +18, -18 and it's a true +48V phantom power... all derived from a single 12Volt input. Outputs are short circuit protected. Just a big spark, but keeps on ticking. Nothing gets blown.
Powering my preamp and my I/O module (input and output trafo, pad, polarity) with Active DI, via 12V wall wart. No hashing sound, no RF leak, no noise. (Well, okay... when you're at 66-72dB gain... but could be caused by everything not in a metal enclosure.)
Output on all 3 rails are typical like below:
Switching spikes on the DC output of about 0.06Vpeak-to-peak, and interval of 33.333Khz. I can set switching freq. to about 60Khz but the spikes get larger.
So I compromised for smaller spikes at a lower switching frequency... i.e. smaller spike/transients, less RFI energy emitted, less chance that it will interfere with sensitive mic pre circuitry.