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In the Forum: Melquiades Amplifier
In the Thread: Planning my DSET
Post Subject: Not yetPosted by anthony on: 12/8/2016
Hi N-Set, I am three quarters of the way through assembling the first power supply to power-up stage so I have not tested the "singing" as yet.  It is something that I have thought a lot about.  First and foremost I wanted a steel skin around the power supply for EMF/RFI suppression as well as trying to mitigate the flow of stray flux into the room from the power supply itself...there is a lot of iron in those boxes.  So I went with relatively thick 4mm steel panels partially for mass (to appropriately load the industrial footers I have ordered), partially for ease of working (I prefer to work with something that is difficult to bend or dent) but mostly to have adequate steel thickness to shield the room from the magnetics.

The 20mm gap was something that I talked to my transformer winder about and that number was decided as a reasonable distance where there would still be some magnetic coupling but its strength would be somewhat reduced.  I could use larger distances for lower coupling but then the power supply case gets enormous and they are big enough already.  Internally, I have a minimum separation between individual pieces of iron of 50mm, usually a little more.  So with the knowledge that I will have coupling I introduced a couple of measures to mitigate it:  the aluminium platforms sitting on sorbothane bushings; a constrained layer damping for the steel panels.

From my calculations, the properly loaded sorbothane bushings should be capable of decent isolation for mains frequency vibrations and harmonics.  I have not tested it yet of course, but if the iron couples strongly enough to the steel panels the sorbothane should be effective at allowing the iron to move a little whilst isolating that movement from the chassis itself.  Whether this works in part or in full is yet to be seen, but that is my hope.

Secondly, on the inside of the 4mm steel panels I plan to apply a vicoelastic polymer and 1mm thick aluminium sheet to act as constrained layer damping so that any ringing is snuffled before it becomes a problem.  This material is specially designed to damp ringing steel panels in industrial applications and has some decent measurements to back it up so hopefully I can apply it effectively.

Cheers,

Anthony

PS:  My hope is that the power supplies feel "soft" to move around...a product of the anti-vibration measures I have used.

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