One or the other

Modern high end audio equipment uses more toroidal transformers than the classic EI. Exceptions seem to be tube equipment. Why? Which is superior to the other? The choice of transformers has as many variables as opinions on which to choose. Bottom line, there are no right answers. Toroids radiate less noise and are more efficient than the classic EI. If I had to choose one reason designers, including us, wind up with toroids so often, these two would be top of the list. It's instructive to remember transformers typically share the same enclosure with sensitive electronics. Radiation from these heavy lumps of iron and copper permeate the space they occupy, and influence hum and noise levels. Choosing the technology with the lowest noise and highest efficiency is somewhat of a no-brainer for most of us. Another advantage of toroids is mechanical noise. Because of the way they are constructed they vibrate less than EI transformers. We're all familiar with the irritating rattle of mechanical transformer hum and a well built toroid can be significantly quieter than its EI counterpart. In fact, quiet EIs are labored over to get that way: super glue between laminations, vacuum impregnation of exotic varnishes. EI transformers typically cost less than toroids. They are easier to manufacture and more readily available in quantity. Most high end audio manufacturers are willing to spend a bit more to make better products and this is another reason for their proliferation in more expensive gear. But why do tube guys use EI? Tomorrow.