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Toroids VS EI Transfomers

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#21
Kuei Yang Wang said:


I would follow this with a simple, open loop, slewrate limited open loop switcher aimed at 50% Duty Cycle. This feeds a Transformers that provides us 12V or 24V eff. Squarewave AC at 76.5KHz, so basically the output is a safe HFAC voltage.
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there aren't a lot of simple things in SMPS design -- but it isn't rocket science either.

Commercial switcher designs optimize efficiency -- as DIYr's, however, we don't have to pursue the least squeak from the pig -- a better/simpler low noise approach would be to use a 40 or 80kHz sine wave, (or a square wave that has gone through a 2nd order filter) -- and a Class B amplifier.

There's an old application note from Linear Technology -- AN29 -- "Some thoughts on DC-DC converters" which discusses the advantages and shortcomings of this approach.
 
#22
I use hand made toroidals im my projects with great success. All they have 1 mm airgap/insulation between the the steel core and the primary winding and the same airgap/insulation between all secondary windings. All cores are 20% overrated to avoid the early saturation and non-linear regimes. I don't think EI trafos are any better than my toroidals.
 
#24
Originally posted by reaction ....I don't think EI trafos are any better than my toroidals.
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I'll take you on over tat one.....with large insulation gap between windings on toroids ....the leakage inductance is probably way higher than a comparable wound EI sandwich bobbin......end result...poorish regulation factor. This may seem odd as nearly all magnetic field is within torus.....but there is a gap between the coupling of windings which on load distorts magnetic flux i.e seeks a shorter route.
However.......that depends on-end purpose of tranny. For light loads......quite ideal.....

Nobody likes winding sandwiched windings on toroids......on EI it's a breeze to do and easier on conformity compliance.

rich
 
#25
I‘m going to build solidstate (BOSOZ and ONO) pre and phono stages soon and was planning to use (order) EI transformers. I have a few questions though and would appreciate comments or suggestions:

1. Transformer windings, what is the optimal solution: Dual bobbin vs. single bobbin plus electrostatic shield, or just a single bobbin and no shield?

2. Should I use separate transformers per channel, even when using multiple filter stages afterwards, e.g. RCLCRC plus series regulator plus RC; so do you think this will still make a noticeable difference ? (I am not talking about my wallet here )

3. Choke input power supply: Ok, this may be more important in class A power amps with high current draw. However, would there still be a noticeable improvement over a more conventional supply, all other things being equal (LCLCRC plus regulator plus RC)?

By the way, I just finished my first project, a ZEN V4 with a separate choke input supply (LCLC), and it sounds really excellent. But as I have no further experience I cannot really claim that the sound is any better because of the supply.

Regards,

Martin.

P.S. This is my first post, hope it comes out OK ?????
 
#27
Reaction wrote:
I use hand made toroidals im my projects with great success. All they have 1 mm airgap/insulation between the the steel core and the primary winding and the same airgap/insulation between all secondary windings. All cores are 20% overrated to avoid the early saturation and non-linear regimes. I don't think EI trafos are any better than my toroidals.
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How did you make it?
I suppose you have an "Infernal" machine of those used in the industry. Or you are so patient and skilled with wires like was my grandmother when she made socks kntitting 12 colors wool wires.
I tried to make a hand windings on a toroid and I was near about to loose my job and divorce. Never mind about divorce but a job is still not easy to find.
I'm talking about output transformers made of many layers all around the toroid a turn after the other, never overlapping and spaced by an even layer of insulation.
I takes me about four to five months to wind an open core 50W OT Like the one on the picture. How long it takes you wit a toroid? I agree for all the rest, but I still dare to try.



An externally hosted image should be here but it was not working when we last tested it.



Bye!
 
#31
Right.
But I'm not full Italian... let me think about it..... not a bit.
I hope this will not sound offensive to none of the Italians around here, but I'm from American origins and about same character.
My whife is 100% Italian but strangely sometimes is more American than I. So she likes to help me in my adventures, at first.
But after a wile... she is still a woman a lot of patience but ready with the stinger. Never say this whire is not so straight...🙄
Come on, all of you know how wemens are.
No wemen in the forum? ...Wow :dodgy:
Sorry for the OT.

But, I'm not so skilled to make myself a toroidal otput transformer with thents of alteranted windings. After I decide to make my last amplifier wether Ultra Linear or Quad I'l take same pictures of the job and post it, so you'll say what you think about it.
Many regards
Larry
 
#33
Hello tube adept, how you doing? Pretty cold up there?
Well, I do ushhhhhhhh.........(not trust so much ) italian trannies builders, and the cost...... WOW. I made amplies only for fun and for few realatives the most time tring making somenthing different. It is just a hobby. So I feel it is worth to waist some time winding them myself. Save some money to spend in tubes that I cannot build and do not preach back to the trasfrormers builder because of some smoke rings. 😉
Sincerely
Larry
 
#34
Larry Lomax said:
Hello tube adept, how you doing? Pretty cold up there?
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ehhh, jep but next week could be hotter 😎

Well, I do ushhhhhhhh.........(not trust so much ) italian trannies builders, and the cost...... WOW. I made amplies only for fun and for few realatives the most time tring making somenthing different. It is just a hobby. So I feel it is worth to waist some time winding them myself. Save some money to spend in tubes that I cannot build and do not preach back to the trasfrormers builder because of some smoke rings. 😉
Sincerely
Larry
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I understand you are realy DIY man, all himself make 😀 , but in your post's about this thema you ask what should be better ?

and if you spend so much money for Tubs I think a it's a mistake to save the cost for Tranis - you know a Trani ist the second part ( first is Speaker ) for sound quality 😉

you can search in Net about Bertolluci Tranis - "Gizmo" Rosenberg write a few words about this and in the sumary wrote that this is a alternative for Tamura/Tango Tranis

Andy
 
#36
Kuei Yang Wang said:
Konnichiwa,

If I want something wound to my own spec I do have links to a number of suppliers, but they are industrial, so don't bother asking for a pair, minimum order on custom designs tends to be 10 - 20 pieces if you supply the full design, more if they design it.


Sayonara
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Well I finally found a positive aspect of manufacturing in
Australia besides living here 🙂

We have access to anumber of fairly small traffo
winders that are more than happy to make whatever you
want WRT any aspect of the design even down to single unit
quantities... if you can pay a bit more.

Cheers,

Terry
 
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