Constrained layer damping tape on toroidal transformer?

Uh, the transformer is not “live”. I use mu metal to wrap transformers and trust me, mu metal is conductive.

Even if the transformer was “live” which it's not, you could wrap it with constrained layer damping tape since the non-conductive viscoelastic layer is the side that touches the transformer.

It is a fact that every transformer has a vibration characteristic, and it amazes me why the majority of manufacturers do not isolate these from the chassis. It is one of the most significant modifications of any piece of gear, whether it be amp, pre, transport, etc, and does enhance sq, ime. I have used roofing repair tape, such as Peel and Seal and USeal, Dynamat, and even mouse pads for this purpose, with a great outcome. Enjoy ! MrD.  

Uh, the transformer is not “live”.

Siri, how does electromagnetic energy transfer work ...

Geez, you’re still trying to argue that? Get real! 

If you're going to use damping tape, try the best - fo.Q TA-102 piezoelectric damping tape. No, I don't make it or sell it (or anything else). But I buy a lot of it for my own use. In fact, I'm probably a bit obsessed with it. Goes way beyond normal mechanical damping, the embedded piezo particles convert vibrations to electrical current, and then to heat which is then dissipated into the tape compound. Many other damping materials only operate on a narrow-ish frequency spectrum, leaving muddy frequencies to bounce around. Many other materials are optimized for high amplitude vibrations, whereas fo.Q is most effective on very low amplitudes such as the vibrations found in audio components. It's slightly conductive.