Constrained layer damping tape on toroidal transformer?

My solution is multi pronged. Remove bolts or at lease loosen them. The only purpose for the bolts as far as I can see is to hold the transformer when the component is shipped.  Place the transformer on pure natural cork square, thickness 0.25”

Next, remove almost all screws holding the printed circuit boards to the chassis, at a minimum loosen them. Use small pure natural cork squares to shim the printed circuit boards, isolating the PCBs further from the transformer.

Next, use 3” or 4” lengths of pure natural cork 1/8” thickness to weave like a serpentine wall around and through stacks of capacitors to reduce their vibration.

Finally, wrap the large transformer with two (count em!) thicknesses of mu metal to shield everything in the component from the very toxic magnetic field generated by the transformer. One thickness of mu metal is 75% effective. Two thicknesses of mu metal separated by 1/4” is 92% effective.

As Bob Dylan says at the end of all his songs, good luck.

@geoffkait - YUP!

You can purchase mu metal on eBay.
You can purchase dampening material already recommended above or go to the Mad Scientist website and buy his reese's pieces things and place them on the transformer with good results.
You can buy transformer covers.
You can buy copper plates and isolate the transformer using double sided tape to hold them in place if you can.
You can buy a separate aluminum box on eBay and move the transformer out of the one chassis.

Happy Listening.

I think someone should jump start Dynaco. You all would have a blast building kit amplifiers! Could be a money maker:-)

Getting rid of DC on the AC line with a DC blocker is the best option. Even a slight amount (less than 1/2 volt) can cause many toroid transformers to become noisy. DC blockers are not expensive.

Most damping materials are also insulators. Transformers need to get rid of heat which can damage their windings. So damping materials can be risky.

Here's a little tip which might help though! The idea of a toroid transformer is less radiated magnetic field which toroids do quite well but they are not perfect. As a result, the bolt that holds the transformer in place should be a non-magnetic material such as non-magnetic stainless. A regular steel mounting bolt is often a magnetic short to the transformer and so its common for the mounting bolt to run considerably hotter than the transformer itself as a result! So replacing the bolt with a stainless bolt can reduce the load on the primary, and can help to silence the transformer.  As a further tip, **do not** use a stainless nut to secure the bolt or you will have to break the bolt to remove the nut. Use a self-locking regular steel nut.


We found this fact out about 30 years ago- but I've yet to run into a toroid transformer vendor that knows it.

Thanks for the tip, Ralph! I think I’ll mount my transformer with a non-magnetic stainless bolt.

I would like to know why you say not to use a stainless nut, though. I build a lot of stainless parts for race cars and for food and beverage and try not to use stainless nuts on stainless bolts due to galling, but that’s only if they have a decent amount of torque applied to them. For lightly tightened things like a transformer, though, there usually isn’t a galling problem. So, why not use a stainless nut? You could always use a little bit of anti-seize if you’re worried about galling.