There is an unknown ferrite toroid. I would like to figure out whether it can be used in an audio transformer, or maybe in a 1:4 transformer on given HF frequency.

The experiment I came up with is following. I can wind a 1:1 transformer using this core, connect one winding to a signal generator and the second winding to the oscilloscope with a 50 Ohm dummy load. Then I can measure Vpp vs frequency with and without the transformer and calculate power loss as 1 - (Vpp_with/Vpp_without)^2.

Is this an adequate experiment? Using this method I could also estimate pase shift and temperature stability. Is there anything else I should be mindful of?

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    $\begingroup$ Ferrite is all but useless at audio frequencies. Powered iron is more suitable, as is of course laminated silicon steel cores. But if the core is "unknown", then it may very well be powered iron. $\endgroup$ – Mike Waters Aug 1 at 16:34
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    $\begingroup$ You might also want to measure the temperature rise of the ferrite. Loss might show up as heating. $\endgroup$ – hotpaw2 Aug 2 at 14:30

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