20-01-2015, 10:38 AM
I don't see the need to convert to DC. Assuming you don't already have one in stock, a simple 50VA mains transformer will cost between £10 and £15 from one of the big suppliers (RS, Farnell, CPC, etc) - perhaps less from places like eBay - and should do the job reliably, and with no RFI or other problems. I'd mount in a die-cast enclosure hidden away under your desk, making sure it has a firm connection to PE and a 1A slow-blow fuse in the primary. Job done 
