Hey Chuck. It depends on what gauge/what current load you're talking about. I made a sweet power cable from Canare Star quad speaker cable. I ran a separate ground wire outside the jacket, spiralled counter to the internal spiral, sleeved all that in a copper braid, then sleeved all that in techflex. The Canare is 11 gauge wire, this thing is about 3/4"diameter, to power my whole home theater. Canare makes a 16 ga. version of this which is ~ 1/4" diameter and more than enough if you're just powering recording equipment. I'd say even their mini star quad mic cable could be enough, and it's very slim, like 3/16"
Peace,
Sanaka