I'm starting to tweak a balanced power Equi=Core 1800. I removed the steel bolts that attach the toroid to the case and will replace with brass. I also plan to cover the tranny with some mu metal I have laying around, but realized is not enough to cover the whole toroid. So I could:
In either case the bottom face will be left uncovered, with the tranny sitting on 3 Herbies dots and very close to the aluminum case.
Which approach is likely to be more effective and why?
Thank you!
- Completely cover the circular top face and partially the side of the toroid. Partially might be around 25% of that surface.
- Completely cover the side of the toroid and partially cover the circular top face.
In either case the bottom face will be left uncovered, with the tranny sitting on 3 Herbies dots and very close to the aluminum case.
Which approach is likely to be more effective and why?
Thank you!
Effective for what?
If you fear magnetic field, "distance" is MUCH cheaper than equivalent shielding. This lump should go as FAR away from your audio as the cords will reach. Further (next room) if you can find a quality multi-outlet box with a long cord.
Toroids don't leak much flux. Do you have a problem or are you just wasting time and money like with the brass bolts.
As stated, distance is the best remedy, and the field diminishes rapidly. Since this is an isolation transformer you can easily place it further enough away for it to have no effect.
As I understand it, transformers (all types) radiate the most from the sides, so cover them first, do whatever with what's remaining.
As a general rule, a toroid doesn't radiate much in the first place, though, and for less distance.
In practical terms, you can buy the toroid with a belt around the circumference from the manufacturer, so wonder why you didn't start there. You'd have enough Mu-metal to cover the top that way (maybe top and bottom).
Mu-metal is funny stuff in some ways. Cutting it can degrade the effectiveness, bending it in sharp corners will degrade the performance, definitely using heat will degrade the effectiveness (welding, soldering) yet gaps are an issue. There should ideally be none or minimal to allow exit of wiring and full coverage as much as possible.
Partial covering is really not that useful. You may well be best off simply by using the sheet you have as is, unmodified, between the transformer and your active circuitry. The best application of mu-metal is a custom fabricated cover from a supplier with expertise in the fabrication of mu-metal products over all six sides or all five (open bottom). But that is expensive.
I'm not convinced all of the effort will have any effective value, since the radiated magnetic energy is already low with toroids, but if you can do it without making it look like a dog's breakfast, and you are interested in learning, have at 'er.
Your most cost-effective solution is probably just a metal cover fabricated from mild steel or aluminum. No heat issues, so you can solder or weld to achieve no gaps, and it's quite effective and costs relatively little. You could also cover gaps with copper or aluminum tape, for example around wiring grommets. In that way you can determine if there is any benefit from shielding the transformer at all, before trying to deal with the mu-metal.
Distance is effective. Use it if you have the room, but be reasonable, as excessive wire length is another problem; you don't want to introduce one kind of interference while trying to reduce another.
As a general rule, a toroid doesn't radiate much in the first place, though, and for less distance.
In practical terms, you can buy the toroid with a belt around the circumference from the manufacturer, so wonder why you didn't start there. You'd have enough Mu-metal to cover the top that way (maybe top and bottom).
Mu-metal is funny stuff in some ways. Cutting it can degrade the effectiveness, bending it in sharp corners will degrade the performance, definitely using heat will degrade the effectiveness (welding, soldering) yet gaps are an issue. There should ideally be none or minimal to allow exit of wiring and full coverage as much as possible.
Partial covering is really not that useful. You may well be best off simply by using the sheet you have as is, unmodified, between the transformer and your active circuitry. The best application of mu-metal is a custom fabricated cover from a supplier with expertise in the fabrication of mu-metal products over all six sides or all five (open bottom). But that is expensive.
I'm not convinced all of the effort will have any effective value, since the radiated magnetic energy is already low with toroids, but if you can do it without making it look like a dog's breakfast, and you are interested in learning, have at 'er.
Your most cost-effective solution is probably just a metal cover fabricated from mild steel or aluminum. No heat issues, so you can solder or weld to achieve no gaps, and it's quite effective and costs relatively little. You could also cover gaps with copper or aluminum tape, for example around wiring grommets. In that way you can determine if there is any benefit from shielding the transformer at all, before trying to deal with the mu-metal.
Distance is effective. Use it if you have the room, but be reasonable, as excessive wire length is another problem; you don't want to introduce one kind of interference while trying to reduce another.
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You would be surprised. When we still had a glass TV you could see color rings all over the side nearest the amplifier which was >1 meter away. I do exactly what is suggested with a mu-metal case. Better still the option is having two transformers mounted on top op each other anti-phase which causes the magnetic radiation to be opposite and cancel completely besides being hum free. You can still cover them as well and it would be unltimate
I understand that mu-metal saturates quite easily, so use it around where you want to avoid magnetic field pickup, not around the source of that field. Better still, just use distance.
jhonny2bad is right about bending of pure mu-metall. I would rather try some magnetic shielding foil or using electrosteel sheets steel Electrical steel - Wikipedia
foil:
Shielding / Screening, Magneticfield shielding, RF & E-Field Shielding, electronic device Screening, Screening panels, Shielding foil, Shielding fabric, etc.
or
3M™ High Permeability Magnetic Shielding Sheet 1380 | 3M United States
foil:
Shielding / Screening, Magneticfield shielding, RF & E-Field Shielding, electronic device Screening, Screening panels, Shielding foil, Shielding fabric, etc.
or
3M™ High Permeability Magnetic Shielding Sheet 1380 | 3M United States
I can see no possible use for a screen.
Transformers radiate from the ends, a toroid has no ends!
Why use brass as a fixing bolt, it has no use, save the look of brass, so no point.
The only problem with steel or brass as a fixing comes when both ends of the bolt are connected together, causing eddy current, shorted turn and loss. Brass would have less effect but then nobody connects both ends of the fixing together.
Transformers radiate from the ends, a toroid has no ends!
Why use brass as a fixing bolt, it has no use, save the look of brass, so no point.
The only problem with steel or brass as a fixing comes when both ends of the bolt are connected together, causing eddy current, shorted turn and loss. Brass would have less effect but then nobody connects both ends of the fixing together.
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