< Picture: Prototype Linear Supply
Selecting the wall-wart
Aside from the electrical specs for the wall-wart, there is the mechanical requirement that you want one with an EI-core transformer and not a toroid as explained here. Fortunately, they all seem to use EI cores.
In Europe, the overwhelming majority of available wall-warts provide a DC output. We can't use that; we need one that gives out AC so we can use the small on-board transformer of the new supply to get us to the 18V Center-Tapped (CT) for the analog supplies.
The rectified voltage from the wall-wart has to supply the +5V, +3.3V and +8.2V regulators. From a voltage point of view, the 8.2V is critical: under no circumstances should the input to the reg drop below the drop-out value. The 8.2V reg is a discrete design with a drop-out of only a few 10's of mV, but still, if you figure in low mains and maximum ripple, you need a 12VAC output wall-wart.
The total current required by the DCX, from all supplies, including the current for the displays of my modified I/O board, is about 1,5Amps. So, you're looking at something like a 20W supply.
[Spec sheet] [construction guide]
It just so happens that one AC-type wall-wart you can get from several sources is a 12VAC-20W type sold for 20W halogen lights. For example, in Europe, IKEA furniture stores carry the FEMTON clamp-on 20W halogen light that sets you back a whopping 8.99 euro and includes a wall-wart. It connects with a small but sturdy plug at the wart. Recommended.
Other sources in Europe include Conrad Electronics. In the USA the choice is much greater, from Allied, Jameco or Mouser. Prices are mostly less than $ 10.
Then the on-board 12VAC -> 18VAC CT transformer. My efforts to use existing mains transformers in reverse direction were not successful. I had this transformer custom-made. (In fact, I had a bunch custom made. Single quantities are outrageously expensive).
Ward Maas from Pilgham Audio who also supplies the kits for my remote control I/O replacement board for the DCX also sources this Linear Supply kit including the custom transformer.
