I used Equitech 1.5Q balanced power transformer a while back. It made a very good improvement on my tube amps. But solid state amp with big power tranny was far less noticeable.
I could be wrong but I think it is because the high voltage tube amp power transformers at 500V tend to have less magnetic reservoir than ideal in effort to contain costs, so they benefit from the large reservoir of magnetic energy in the huge balanced transformer. Solid state power transformers of <50V, can have more than adequate VA rating for the performance envelope without cost being a big problem.
