Just for fun I decided to build another SET amp and this time I'm using the 2A3 output tube. I found a schematic here:
http://gabevee.tripod.com/2a3diy.html
I used Hammond iron for the mains and output transformers the 270FX main and two 125CSE's for the outputs. I was able to build the whole thing for around $300 total! Playing through a set of 20 year old Radio Shack bookshelf speakers this thing sounds surprisingly good with a nice sweet tone. I'm really impressed because these output transformers are not really intended for hifi use.
I'm not sure how many watts it really puts out but I'm thinking 3 or 4 a side. It's plenty loud here in my basement with nice dynamics.
If you're thinking about giving a single ended "flea" tube amp a try this would be a tough project to beat for simplicity and performance. I built it totally from scratch in about 2 nights about 8 hours. I have some cleanup work to do and I'm just testing it right now but so far, so good.
I do think there's an error on the schematic and that the coupling caps should be .022Mf and not .22 as listed. I used .022 on my build and it sounds fine but I'm going to experiment in that area. I'm using some Orange Drop film caps for now.