Power Supply Case Size


2010-06-05 5:28 pm
Hey all-

I'm working on enclosing the power supply for the mixer, but I was considering whether a small or a large case for the PSU is best.

(PSU details the way it appears on my workbench)
I've got four chassis-mounted transformers (largest one is the the size of a cube of floppy discs) and an auxiliary PCB-mount transformer on the right side, bridge rectifiers, smoothing caps, and the cooling circuit regulators in the center, and all other regulators on the left side. For controls, I'm using a key-operated switch for the master power switch, and an SPST switch with a red LED for the phantom power master switch. Around the back, I'm using an IEC power socket for AC in and DB-9 socket for DC out.

Is it best to use a small case that only has enough space for all the components or a large case?
It depends. A compact case or chassis will tend to be stiffer, helpful if you have heavy components like transformers and chokes. On the other hand, a 17" (or so) box can be rack mounted. In either a studio or live application, there's bound to be a rack nearby. More space means you can keep electrolytic caps away from hot things, which should extend their life. And if you want to add something in the future, you've got space. And more space makes it easier to route wires neatly, or keep low-level stuff away from noisy AC. And it's just plain easier to work inside when there's more room.

DB9 wouldn't be my first choice for DC power. I feel it is a bad idea to use what is normally a data or signal connector for DC power. XLR connectors come with pin numbers greater than 3 (up to 7 or so), which aren't commonly encountered. They lock, will accept a decent size wire, and aren't too expensive.

(Other alternatives:
I'd go with an Amphenol military-style circular connector, but that's because I've got a bunch of them surplus. They're expensive and complicated to order because there are so many options. There's Jones connectors, which cheap, rugged and handle plenty of current and voltage, and come in various genders, mounting styles, and pin counts.)