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In Reply to: RE: A TT tweak posted by unclestu on June 28, 2015 at 17:07:57
Hi Unclestu
In fact i had started another thread here asking for tips to reduce emi in a turntable. I think your mumetal copper shielding answers that question. Thanks.
I had a few doubts.
1. When you make this sandwich, typically how many layers of mu metal and copper does one start with?
2. Would the mumetal layer face the motor and the final outside layer be copper?
3. Is there any particular thickness of copper and mu metal does one use? Is thinner the better?
4. Is this mumetal copper sandwich kept close to the motor?
TIA
Follow Ups:
1. You can run as many layers as you like, Even a single layer makes an audible difference. I like to run three layers2. Yes I prefer the mumetal inboard and ending with copper outboard.
That being said, it is important to note that copper , which also provided electrical shorting of the magnetic field also provides an amount magnetic isolation between the layers of mu metal like the layers of laminations on a transformer. It is more important to isolate the mumetal layers here because the fields involved are smaller in intensity, particularly the field from the cartridge.3. I use mumetal and copper foil, as they are easier to work with: 15 thous thick. Thicker mumetal sheet needs to to be cryogenically treated in order to retain its magnetic properties. Foil can be shaped without the need
4.Yes place or adhere the sandwich as close to the motor as possible for best results. You can use double stick tape or even tape over the sandwich. The tape will not affect the magnetic field unless it is metal tape. Of course you can use copper tape
Edits: 06/30/15 06/30/15
Hi Unclestu
When you say adhere it with a double tape, it can be adhered on one side to the body of the motor, right.
Yes. I used to wrap the entire motor assembly, but then it became a PIA to install as you had to do it layer by layer since the diameter is constantly expanding. This simply address the field facing the cartridge, Simpler and IMHE just as effective. I use thin double stick tape on the motor body side. I do sort of pre-shape the mumetal strip first though to place less tension on the tape and I do use Scotch VHB tapes (very high bond).
You can still use the Shakti's in conjunction. If you have a TT like the older VI and SOTA you can place the shakti above the motor, on the motor cover. On a Linn type, try directly under the motor.
YMMV and FWIW
Hi Unclestu
Am based in India. So will have to order the self adhesive mu metal and the 3M self adhesive copper foil from the US. I don't want to go wrong with the specs.
Is this what i need to order
http://www.partsconnexion.com/CONNEX-76151.html
http://www.amazon.com/3M-Conductive-Copper-Shielding-Adhesive/dp/B0000WRJIO
Check out the lessemf.com website: lots of shielding products for reasonable prices and amounts. Ignore the mystical stuff....
Shaktis work but they are rather like a shot gn in terms of suppressing EMF. Their working principle is that the brick forms a internal waveguides, focusing the EMF absorbed onto quartz or quartzlike crystals. As such they work well over large transformers, and power supplies, as well as motor assemblies
Hi unclestu
Does this mumetal copper sandwich also work for power transformers in the power amp? Or is only copper foil around the transformer enough? At present there is no hum or anything. Just looking to see if i can further improve on the microdynamics
Yes it does, but you have to be careful as there are various types of transformers. The standard EI cores are fine, but the toroids require a ring or washer shaped form for effective use.
I use the mumetal/copper sandwich to guide the magnetic fields, NOT to attempt to completely shield anything.
Thanks Unclestu. Will look up lessemf.com
Thanks Unclestu. I have a EMT direct drive turntable . Appears to be well engineered. Will first try the mumetal sandwich.
Does the Shakti stone used on a power transformer in the amp have any negative effect on sound? Like for example does it thin out the sound? Or reduce dynamics? Like you i too use the Rethm speakers and would not like to lose out on the speed and dynamics.
Thanks Unclestu. Would using a Shakti on line stabliser also help?
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