Yes, you can break in power cords. The FRY PRO does this. I'm not sure yet what the optimal arrangement is, but I typically connect a signal to both L and N (different polarities) and ground the E. Run this with one end open for awhile for voltage mode. Then short circuit the far end, all three prongs. This will force a current mode burn (which is more effective). At this point, I think it would also be best to make polarity of L and N the same, to insure current returns via E. The 3-wire cord is a bit more difficult than the 2-wire types.
Also, you won't need a 100 watt light bulb. This is a myth I am trying to dispel. For break-in of cabling, forget what the ultimate application is. It does not matter. We have to break-in the materials and complete the manufacturing process (adding cryo would be good too). Power cords break in just like phono wire. Do not mix the application with the burn.
For step-ups, I run them at full output level, not with an iRIAA. Even more effective if you short the secondary outputs, which forces a magnetization flux in the core. I use the ESR of the winding as the load. There are a number of ways to hook up, but I always find the current mode to be best.
jh
