Idle thought as I was looking at the various DIY tube amp kits. It seems like the most expensive part of the average tube amp (especially the large >100 watt units) is the transformers. I'm a building engineer by trade so I have access to both a lot of scrap industrial transformers as well as industrial supply places that can order/make whatever I want for relatively cheap. However, I only work on AC line voltage and modern lighting and hvac fixtures, so the intricacies of tube amplification is still a foreign world to me. Obviously the exact specs vary depending on how many of what kind of tubes you are running, but I'm hoping for a set of guidelines to get started on.