EI Vs Toroidal

The toroidal in my F5 clone hums surprisingly loudly. Virtually no noise at all through the speakers, but you can hear that toroidal humming away from 2 or 3 feet away. It almost makes a grunting sound when I power it up. 

Huh, I had always thought that Toroidals made the best transformers.  Then a newer company called Schiit(of which I've become a fan after trying one of their DACs) released a 100 x 2 wpc amp featuring an IE transformer, stating that they prefer that over the toroidal design.  

I was surprised, but apparently that little amp holds its own.  Now I read this thread, and realize that the science isn't as settled as I thought!

The toroidal in my F5 clone hums surprisingly loudly. Virtually no noise at all through the speakers, but you can hear that toroidal humming away from 2 or 3 feet away. It almost makes a grunting sound when I power it up.

Toroids saturate easily if there is DC on the AC line. A common cause of this might be a heater running at half power- it is only drawing power on one half of the AC waveform. This causes half of the waveform to have a lower amplitude- and thus can be regarded as DC on the AC line.

Its easy to block with a simple device, and may silence the transformer. The amp might also sound better too, as the transformer might then deliver a cleaner waveform to the power rectifiers.

The grunt at turn-on is common with many transformers, toroidal or EI core.