I am not a builder so my experience is largely second hand. A local shop builds its own tube electronics--mostly line stages, phono stages, amplifiers and integrated amplifiers. Many of these custom components are extremely expensive. For many of these builds, Edcor power transformers (the blue case you mentioned above) are used. This shop builds stuff largely with price of parts NOT being an issue--sound quality and reliability is what counts. Edcor makes a lot of transformers, and I don't know which models are favored by the shop, but, they are quite hefty in size.
What are the different Levels of quality in Power supplies Transformers and Chokes
I was in another thread started by @mithc2 and I didn't want to take over the thread with my questions but @fuzzbutt17 from Mojo Audio was talking about the different level and types of power supply. What I would like to know is about the quality of parts of the power supplies including Transformers. I see blue incased transformers in several components. Is that a nice transformer? Why is it incased? I would like someone to comment on the differences in quality in transformers chokes and Capacitors.