What's the big deal about toroidal transformers?

[petespaco]

What is special about toroidal transformers?
  I just saw this one:
https://www.banggood.com/Input-220V-200w-to-AC-12V-Ring-Transformer-Toroidal-Transformer-Power-Amplifier-Transformer-p-1595029.html
It costs USD$62 and it makes 200 watts of 12 volts.
I could rewind a lot of microwave oven transformers for that amount of money and get 4 or 5 times the output power.

Pete Stanaitis
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[davekni]

Toroidal transformers are popular for analog audio equipment because they generate much less stray magnetic field, so induce less line-frequency hum into adjacent conductors.

They are also a bit lighter for a given power rating.  However, a higher fraction of that weight is windings (usually copper).  That adds to cost,  besides the more complex winding machines needed.

[rikkitikkitavi]

They are quite a lot lighter acutally, but that is because all core length is covered in winding, ie less iron is necessary.

I have a coupla large ones, 2-2,5 kVA that would be very heavy as EIs.

A normal MOT core is about right for a 300VA EI for continous use at about 95-96% efficiency , when considering winding window etc.

A new EI transformer is not cheaper than a toroidal, unless made in large quantities.

I have not paied more than maybe 50 bucks / Euros for all my kVAs of toroids. It is a matter of how deep you dive into the dumpster...