A toroid will have much less radiation/crosstalk
I suppose its an iron powder core for the small output inductor, and very few windings are needed
Pure iron core I would avoid, if possible
But I dont understand whats new about it
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Practically non-magnetic core
The sonics of the type 2 core are no where near as good as an air core and if I can't find an inductor that will shield AND sound good, I will have to abandon class D and go back to class AB.
I would audition the type 0 To try to get closer to the sonics of an air core while still containing EMI enough.
The sonics of the type 2 core are no where near as good as an air core and if I can't find an inductor that will shield AND sound good, I will have to abandon class D and go back to class AB.
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Maybe it's iron powder, but it has only 50 % bigger permeability then air, so I would say its almost nothing. Al=1.5 nH/turns^2 --> 20 uH needs 115 turns. I wouldn't say it's very few. A little bigger plastic or wooden ring will do it as well as this expensive ****.
sendler! If you want something like air-core, then use air-core! If the choke forms a toroid, then the radiation will be low. But it needs much more wire then a usual air-core coil!
The type 0 core is simply phenolic plastic, so it is equivalent to having an air core, except that you have something on which to wind the wire.
Air cores do pollute
I have some single layer cylindrical air core filters built but they do pollute an AM radio up to 20 feet away so I only run them for brief comparisons. I have adequate filter response with the inductors down to 6uH so I am looking at 30 inches of wire with the type 2 core versus 90 inches. It's worth a try if no one else has already done it.
Ahh, ofcourse
THEN a hardwood toroid core with rounded edges would be nice
Make it yourself, thats not difficult
The best for free
🙂
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No, the core doesn't pollute. The wire does, if it's not compensated by other wire (like at a usual toroid). The toroid core does not shield!
Multiple layers?
What are the draw backs to multiple layers of windings on a toroid if you commit to two full layers? They are used in transformers but rarely seen for inductors.
What are the draw backs to multiple layers of windings on a toroid if you commit to two full layers? They are used in transformers but rarely seen for inductors.
IMHO, the ability of toroids to contain their fields is vastly overrated. Everybody just keeps repeating what they've heard; sure it's better than a solenoid wound coil, but by no means radiation free. It's more different than an E-core iron transformer, rather than wildly better, and you can still get into trouble if the location is poorly chosen. The type 0 is, as said above, non-magnetic. Plan on using a lot of wire!
As said before a type 0 ring is unmagnetic as is implied in it's name (inductance x0), and is as such just a very expensive curtain ring. If you want to experiment with this I suggest visiting the local home depot or similar store and look for some wooden or plastic curtain rings in a usable size, no need to pay 3 more middle men a kick back.
Soneone asked wha one shouldn't wind multiple layers onto one core. Well this way that inductor's unavoidable parallel capacitance would get too large.
If you want to avoid stray fields as much as possible and achieve a highly linear inductor then take an air-core with a magnetic path around it. One possible example would be an RM core with a huge air gap. This should be possible with an ordinary RM core, some patience and a Dremel for instance.
Regards
Charles
If you want to avoid stray fields as much as possible and achieve a highly linear inductor then take an air-core with a magnetic path around it. One possible example would be an RM core with a huge air gap. This should be possible with an ordinary RM core, some patience and a Dremel for instance.
Regards
Charles
Yeah - the reason toroids contain their fields is because the flux stays confined and had nowhere to come out if the "end". That only works if the confining medium has a high perm relative to air. Use air and it will leak! With even windings all the way around, far-field cancellation might be a bit better than a solenoid in some orientations, but not others. Locally, in the circuit next to the coil, it's like an air core coil.
I would expect the -2 mix material usually used for class D to have higher EMI than mix 26. 10 perm is better than air, but there will still be fringing flux.
This is not true. If you have a toroid inductor, with well distributed turns, with air core, and close, parallel "legs" the magnetic field must be cylindrical symmetric. For example, in the equator plan: every individual turns have a magnetic force which is paralell with the equator's plan. So if there were non-zero result, then it would have been tangential. But applying Ampere's law to this says that it requires a current which flows in the direction of the axis, wich is not true. In similar way it can be proven for every points that outside the coil none of the components can be different from zero.
The leakage comes from imperfections, for example when you wind the turns in a way that it goes around along the core, then you make a single turn choke in excess the toroid. Not equal distances are the other source of leakage.
Problem is that imperfections are unavoidable because the very nature of winding a wire around a toroid will cause imperfections.
Yes, unavoidable (at least entirely), but
- these are secondary effects, and much weaker then with a solenoid
- if you know about them, you can decrease them. If you ignore them, then they can be bad.
- if you know about them, you can get ready for it.
- the question was if the low leakage is caused by the magnetic core, or not. I answered to this question. (Not.)
- these are secondary effects, and much weaker then with a solenoid
- if you know about them, you can decrease them. If you ignore them, then they can be bad.
- if you know about them, you can get ready for it.
- the question was if the low leakage is caused by the magnetic core, or not. I answered to this question. (Not.)
un-cored leakage experiment
Rather than waste time and shipping costs on the 1.5 AL type 0 cores I will wind some air core toroids to see about the remaining leakage. It should be easy to do, starting with an over value cylindrical single layer coil and shaping it into a toroid. Local leakage hasn't been a problem as the solenoidal air core inductors I'm using as a reference sound really excellent in practice. So the next hope is to keep the sound but reduce the far field radiation to a level that can be contained in a metal enclosure.
Rather than waste time and shipping costs on the 1.5 AL type 0 cores I will wind some air core toroids to see about the remaining leakage. It should be easy to do, starting with an over value cylindrical single layer coil and shaping it into a toroid. Local leakage hasn't been a problem as the solenoidal air core inductors I'm using as a reference sound really excellent in practice. So the next hope is to keep the sound but reduce the far field radiation to a level that can be contained in a metal enclosure.
Iron casing
If you are worried about the small leaking magnetic flux, then make a sheet-iron casing for the coil. Leave some air between the coil and steel sheet.
If you are worried about the small leaking magnetic flux, then make a sheet-iron casing for the coil. Leave some air between the coil and steel sheet.
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