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The VAC Standard tubed preamp power supply is in a separate metal canister. It has a huge transformer,and the case, even though sealed radiates a LOT of EMR.
How can i contain this? Crystals are not gonna do. Can I make an additional Faraday cage? and just have it a few inches bigger all around?
The Power supply has a long umbilical cord (for the preamp) and for good reason!!!
But i would like to cut all the stuff radiating in my system. So asking for assistance here.
The umbilical from this supply to the preamp is also the biggest EMR emmitter in my system! The cord is unshielded and i am also working on a way to either shield it, or something.
But the power supply is already in a sealed case, and so WHY?? is it radiate so much anyway?
I mean the power supply shoves a ton of energy into any metal object around it. If I place it near the metal rack, The entire rack is then radiating EMR!!
Follow Ups:
Far less emmisions from the case.
So now to work on the umbilical cord.
That's good news. Should work well with the umbilical.
Seems the umbilical with a copper shield made the music harsh and shrill. I guess the bad stuff emanating from the cord really wants out for a good reason. So not blocking it, need to absorbe it. Antistatic foam is the next attempt.
I see. Always good to experiment. Keep us posted and I may even give it a try.
.
Wadia 2000 DACs had a specially milled aluminum case with four sections: one for the power supply, one for the digital section, one for the analog output section and I forget what the fourth section was for. The only connection was very small holes through which the wires were routed. Obviously an expensive approach to eliminating cross talk between sections.HK HD 7500/7600 CD players had a slightly different approach: the ground planes of each section were distinct and separate, meeting at only one point. Apparently HK engineers felt that the ground plane itself was responsible for a lot of the RF emissions.
Although many have condemned the use of ERS. I have had excellent results using it, even on components with metal chassis. I line the chassis with it and also glue small pieces upon the various IC's and other components on the board (voltage regulators emit a lot of RF although one needs to be very careful of the heat requirements , or rather the cooling requirements.
I was initially very puzzled about the effects of ERS, again like you, assuming that the metal chassis should have been enough to shield the component from RFI. I believe what may be happening is that the metal surfaces may simply be reflecting the RFI inside the chassis rather than absorbing it. The ERS has the paper cloth like feel and it may simply be using the surface as an absorbent "sponge" for the rf.
As a clue, the HK CD players had a brass shield over the DAC chips but they also had what looked to be a velor patch on top of the shield. I assumed ( never tested it) that it was a conductive patch. I would think your conductive foam should work very well here, BTW.
The huge transformer may also be at issue too. If you place the DAC power supply on a rack, try placing some magnets ( even refrigerator magnets will work) on the rack legs which bracket the power transformer. This will contain the eddy currents generated by the transformer and noticeably aid the sonics. This will screw up any TT lying on the rack , however, that is, if you run a TT
Stu
PS: BTW, My modified HK sounded better than the Wadia combos and at a significantly lower price.
Edits: 04/06/11
does the unit supply ac or dc to the main chassis? does the umbilical detach at one or both end(s)?
The power supply is for a four tube preamp. So i would just say it has to supply the power for the tubes. The circuit inside the preamp itself is pretty simple point to point wiring, and few doodads added in, real straight-up simple circuit. (the only complexity is the home theater pass through wiring)
The cord is permanetly attached to the body of the power supply and a multipin screwdown ring clamp is the connector at the preamp end.
Inside the Powersupply is a REALLY big old fashioned square transformer, 5" by 5" and 4" wide.. and a few medium sized caps, a tiny circuit board with a few bits on it.
Sounds like it is feeding dc to the preamp. If the main preamp has an even number of tubes, and there is no tube in the psu, thenit is solid state rectification (if the caps in the psu are electrolytics or really huge film caps, then it is almost surely feeding dc to the preamp.
i would think that a dc feed would have little grunge on it. the big transformer on the power supply unit (psu) could be shielded with mu metal or tishield, but you have to be careful about not trapping heat that neds to be vented from the psu.
happy hunting!
Mark
I may try to shield the umbilical at least were it is going up the rack. And perhaps something to add an extra shield all around the PSU caes?
d3vkb, separate power supplies are darn sensitive. Even orientation has an effect on sound quality. Here's a fun tweak. Find some aluminum foil tape you may have lying around the house and place it over to an open socket with your hand but make sure you do not place it into the socket. Then grab your trusty non-contact voltage detector and test. I use the same concept around my male and female IEC plugs by cutting a 6 inch strip and taping it around the connector. Its an effective electromagnetic shield. There is a Marantz video floating around youtube where somebody uses a copper union (tube) around a pc plug that does the similar trick. You can use copper tape if that is more to your liking as well. Perhaps you can figure a way to minimize EMI at your power supply too even though it may look strange if you taped the outside of the unit.
Edits: 04/07/11
And I do have some aluminum tape laying arund.
I did note that most outlets with plastic covers emit stuff, but metal covers block it. (i have a few decorative brass outlet covers)
The body of the VAC PSU is quiet with a VPI brick on it, and another alongside. (I was using the bricks to stabilize just with the weight, one of my TTs shelf) Now if i could just calm down the power umbilical. I had covered some CD player cords with copper (which has gotten pretty ratty. I might take that off anf try to reuse it to cover the umbilical, then tape over that with the Aluminum tape. At least the portion which climbs the rack.
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