PT magnetic field

[hylaphone]

Regarding the magnetic field of a power transformer, is it attributed more to the low voltage, high current windings? Or vice versa?

If best orientation of the PT and OT isn't enough to quiet down the hum, would I be better off trying a toroid for the filament supply or HT supply?

[Helmholtz]

I guess the outermost winding (whichever this is) contributes most to close-distance outer magnetic field depending on orientation.
But even an unloaded PT has a leakage field.

What transformers, what orientation and distance?
Are you sure the hum is from transformer coupling?

[xtian]

Are you asking a theoretical question, or do you actually have transformers in your hand?

When energized by mains AC, a PT radiates EM at idle--doesn't even need to be passing current. I have built about 60 custom amps over 15 years, and almost every one of them was a custom or experimental design, so I positioned the PT/OT/choke and listened using the headphone trick to help arrange each project. I could find a good null point for each one, even with PT and OT adjacent to each other.

[hylaphone]

Interesting. This is more theoretical as I approach a new project of a 200W bass amp...
Thanks for the insight!

[xtian]

In that case, go for a toroid! No radiated EM, a bit lighter in weight.