Constrained layer damping tape on toroidal transformer?


Is it safe for me to apply constrained layer damping tape (aluminum core) directly to the exterior plastic wrap of a toroidal transformer?  Are the wire wrappings around the core insulated?  
tomask6
No.

You could insulate the transformer, causing it to heat up, and the conductor itself could have currents forced in it, causing it to heat and melt.

If you are trying to reduce physical hum, better to look at the mounting method and eliminate DC on the AC line.

Best,
E
Place the viscoelastic material under the transformer. Thus it will be constrained by the transformer. Loosen or remove bolts to isolate it from the chassis. Problem solved! 🤗
@geoffkait is right, but don't use anything conductive!
Yes Agree that you should try a non conducting material to dampen your transformer.  If it does get too hot Sorbothane in a constraining package or pillow might do the trick.

I just got back my Ayre amp that the manufacturer  updated/repaired.  They put tape on the cooling  finds  and told me Ayre recommends it to reduce unwanted resonance.
I just bought a toroidal transformer for a project and it actually came with a foam mounting pad for isolation. I plan on gently tightening the mounting bolt so the foam doesn’t compress too much. Not bolting it down at all seems a little too risky.
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.
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.
Ironically, perhaps, mu metal, a high permeability low frequency alloy commonly used to shield/absorb magnetic fields of transformers, including toroidal transformers, contains ferrous metal. Not sure I would pay too much attn to a ferrous nut. Or ferrous bolt for that matter. Besides as I already commented, bolts on transformers is a rather dumb idea, with the exception of shipping the component, quite unnnecesasry and bad for the sound. 
Sorry, but not bolting a high voltage component to the chassis is idiotic. Plus, if you isolate the bolt and transformer correctly, it will be like it’s not bolted in at all until you actually need to count on the bolt, like if you pick the component up and forgot you didn’t bolt it in, someone bumps it, etc.

Why not leave the transformer outside of the chassis and just run the wires into it? I mean, you might as well go all the way if you’re going to be dangerous about it.
If you can’t remember eat more fish. 🐟 🐠 🐟 🐟
@ketchup
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.
Anti-galling compound should work fine...  I'm just nervous about it perishing and being a problem years down the road.

Just for fun, if you have one of those lazer temperature sensing gadgets, its easy enough to see that a ferrous bolt runs considerably hotter than the transformer itself. Its also easy to see that the latter runs cooler once the bolt is replaced.

I ended up wrapping the primary and secondary tap wires of the transformer with a small piece of constrained layer damping tape to great results. Smoother, quieter, more musical yet still dynamic.