SUT shielding

[Barry]

I suppose the obvious question to ask is are you already troubled by hum and noise? Is the case completely made of metal? And if so what is the metal - aluminium?

[RothwellAudio]

Dave uses a very unusual mix of shielding elements including copper, steel, mumetal and maple...

Maple? Really?
Shielding against magnetic fields requires a ferrous material, preferably of high permeability. It shouldn't really cost three times the transformers inside.
However, un-shielded but carefully sited transformers placed well away from mains transformers can have less hum than shielded transformers simply plonked down on top of another piece of equipment.

[farflungstar]

I'm sure that for just shy of 2k for the case I could come up with something....
Adey

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[Reffc]

Maple? Really?
Shielding against magnetic fields requires a ferrous material, preferably of high permeability. It shouldn't really cost three times the transformers inside.
However, un-shielded but carefully sited transformers placed well away from mains transformers can have less hum than shielded transformers simply plonked down on top of another piece of equipment.

This.


When I was developing SUTs, I used Mumetal shields and I can tell you, they don't cost £2K to make or anything close!

Shielding is really mandatory for small signals subject to and sensitive to EMI, it needn't cost the earth and can be simply effected by housing the transformers within their own (potted) shielded enclosures then placing those within a secondary shielded enclosure for good measure. It's also important to get the earthing right to avoid excessive hum.

[mac72]

Quite often to make proper magnetic shielding more than one enclosure must be used , is quite common to use steel shield as external one because of its high saturation then use mu-metal enclosures , as mentioned earlier bending should be avoided as it lowers mu-metal properties of the affected areas.
Very good remark about positioning and earthing, this shall be your first step , do it right and you might find no need for magnetic shielding

[mac72]

You're right, it needs to be solid material for magnetic shielding.

Not necessarily, as long as diameter of the hole is smaller than length of the wave , faraday shields protect from high freq. magnetic fields , we talking radio freq. above 100kHz when thickness of material used is around 1mm.
It could protect from 50Hz EM fields as well but thickness of used material must be more than skin depth of used material , if you want to use copper for example , we talking about min 20mm of thickness .

[Mike Adams]

I looked at some of Dave's SUT too.

They are quite a bit bigger than most SUTs and I believe Dave houses them separately, which I guess goes a little towards why they are so expensive. (I believe Jeff Day has some of these...)

In the end I chose to get HM7s as they are well shielded as standard which mean building them into a box was more within my skill base...

[Arkless Electronics]

My I ask the op has he considered a head amplifier instead of an SUT? There does seem to have arisen lately a belief in some quarters that a SUT is the best way of amplifying the small signal from a MC cart and that it is a better way than a good MC input on a phono stage or a head amp.... I strongly disagree! It's yet another of those "trends", "fads" based on "old wives tales" etc that unfortunately blight our hobby

I make a high end head amp which, IMHO, is more than a match any SUT and will undercut the expensive ones as well

[Arkless Electronics]

Not necessarily, as long as diameter of the hole is smaller than length of the wave , faraday shields protect from high freq. magnetic fields , we talking radio freq. above 100kHz when thickness of material used is around 1mm.
It could protect from 50Hz EM fields as well but thickness of used material must be more than skin depth of used material , if you want to use copper for example , we talking about min 20mm of thickness .

You seem to be mistaking electromagnetic field and magnetic field....

[farflungstar]

The only reason I'm considering a SUT is for exact impedance matching of the shilabe with my Vida - the Vidas high setting is 100ohms but following the general rule of thumb of x10 means the shilabe should see 160ohms, though some folks prefer higher. I wish the Vida offered a higher setting as it's performance is astonishing as is the noise floor.

Adey

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