Maybe the Vibb Eaters Mini stops vibrations from the transformer? I had vibration problems with my WA22 when I first got it, but it's been fine since I upgraded the power cord and added a power filter. A tech I know mentioned that I could open up the top and fill the compartment with something like this:
http://www.ebay.com/itm/8-LBS-Glass-Bead-MIL-3-A-20-30-grit-Coarse-Media-Reborn-Doll-Abrasive-/121836693679
The effect from Vibb Eaters is significant in my case, obviously darker background, intensive layering/ dimensional experience resulted in better imaging delivery, refer to quote below, not only absorbing vibrations but also magnetic field interference.
Quoted from:
http://www.entreq.com/products/accessories-17667732
"
‘Vibb eaters’.... for electronic equipment.
These have a special sand mixture which leans towards the optimisation of the magnetic characteristics. They still of course offer a greater stability to the chassis of the equipment as well as absorbing vibrations but the ‘Vibb eater’ also neutralises a part of the magnetic field from the electronic equipment. You will always have to experiment to find the optimal position for the ‘Vibb eater’ but we usually find the best place to start is closest to the power cable in-let or the products transformer."