How to improve power supply?

All transformers should be wrapped with one or two,layers of mu metal, a highly permeable alloy. Toroidal transformers are no exception. In addition, if feasible, should be decoupled from the chassis by removing the bolt and by placing a layer of cork beneath the transformer, isolating the sensitive circuit boards from the transformers.

Geoff Kait
Machina Dynamica

Good morning Geoff and a big thank you. Listening to classical gets better for me with every refinement. I will look into Mu metals to find the most appropriate and post it here. Using the cork makes perfect sense. Maybe there's a sandwich with cork that can be more effective. Looking into it. Enjoy the day :-)

Try a couple sheets of Sorbothane, with the cord between. Be certain that the bolt(s), holding the x-former, remain(s) free floating(isolated from the chassis) as well. Good info: (http://www.sorbothane.com/standard_product_guide11.php)

Keep in mind, if using MuMetal sheet; If it has to be bent(to
any great degree), annealing in a hydrogen atmosphere is
recommended, to restore the grain structure/permeability.
MuMetal foil is also available, if you can arrange a way to
surround the transformer with it. The foil doesn't require
annealing, unless severely formed or heliarced. One source:
(http://www.lessemf.com/mag-shld.html)

Thanks Rod, that makes sense. So basically I take it there should be 'isolation' material as a "washer" between the afixing bolt head and transformer surface as well as under the transformer.
I am going to check the torque required to loosen the bolt, which will be more than it needs to be retightened. Thanks for the SORBOTHANE idea. Coincidently I've read a bit about it lately and it sound good to me. If it's good enough for NASA and the Liberty Bell--it's good enough for me!