Relationship of amplifier sound to transformer quality?

One of the reasons Jadis electronics sound so good is their hand-wound transformers. 

If the transformer is not wrapped with low frequency high permeability mu metal sound quality will suffer. No two ways about it. The toxic effects of the induced magnetic field extends to everything within what, about a foot of the transformer? At least.

ptss---The DIY guys who build their own amps are the ones to ask about transformers. They all have their own personal favorite(s), but you see the name Magnequest a lot. rcprince is right, the Jadis transformers are really nice, but proprietary---you can't get one (without buying the whole amp!). Give Modjeski a call---he's pretty open about recommending stuff like that.

If the transformer is not wrapped with low frequency high permeability mu metal sound quality will suffer. No two ways about it. The toxic effects of the induced magnetic field extends to everything within what, about a foot of the transformer? At least.

Magnetic field outside of toroidal transformer is theoretically zero.  It is completely contained inside of the core.  Toroidal transformer has no gaps making it more sensitive to presence of DC voltage.

EveAnna Manley is so convinced of this that they make their own trannies in house.