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Old 28th November 2012, 09:19 AM   #11
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Quote:
Originally Posted by TheGimp View Post
Nice response waveforms.

Can you show us a 100Hz square wave?
This is square wave response WITHOUT DC BIAS!
Keep in mind that under DC bias, the magnetic permeability is raised at a factor of 2-2.5 depending on biasing and magnetic circuit gap. So this graph is of no use. But if you are experienced in OPT graphs without DC biasing, this might tell you something.

Take care.
Peter
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Old 29th November 2012, 05:01 PM   #12
Tyimo is offline Tyimo  Hungary
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Quote:
Core type: Double C Core
Material: Cold Rolled Grain Oriented silicon steel cores at 0.1mm ribbon thickness
Hi!
Could you tell me where an I buy such a C Core material?

Greets:
Tyimo
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Old 29th November 2012, 05:06 PM   #13
TheGimp is offline TheGimp  United States
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Quote:
Originally Posted by tinitus View Post
but you can use paper in oil caps with high voltage ? whats the difference ?
The difference is the oil which acts as an insulator. It has a higher breakdown voltage than the paper or air.
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Old 29th November 2012, 09:10 PM   #14
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A comment on bifilar magnet wire windings for mains use... CSA will not approve them for 240V use, though UL will. I tested a product for line surges (2KV) which failed repeatedly due to breakdown between the two bifilar primaries, connected in series. It proved necessary to add an MOV (Metal Oxide Varistor) to protect this transformer. Other transformers with layer insulation between the dual primaries had no problem with the 2KV surge test. Some switch-mode transformers use triple-insulated magnet wire which would be another story... but it's too expensive for use in mains transformers.
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Old 29th November 2012, 11:17 PM   #15
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I agree! Forget bifilar windings above 400Volts, too risky unless you use double insulation material. Manufacturers give out complete data for insulation breakdown, go by the safe side, dividing by two.
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Old 30th November 2012, 12:47 AM   #16
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Quote:
Originally Posted by petavgeris View Post
This is square wave response WITHOUT DC BIAS!
Keep in mind that under DC bias, the magnetic permeability is raised at a factor of 2-2.5 depending on biasing and magnetic circuit gap. So this graph is of no use. But if you are experienced in OPT graphs without DC biasing, this might tell you something.

Take care.
Peter
I have seen this said before but I have never been able to see it in practice except when the applied DC shrinks the physical gap.

dave
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Old 30th November 2012, 07:04 AM   #17
Tyimo is offline Tyimo  Hungary
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Hi Petavgeris!
Quote:
Core type: Double C Core
Material: Cold Rolled Grain Oriented silicon steel cores at 0.1mm ribbon thickness
Could you tell me where can I buy such a C Core material?
I have only 0.25-0.3mm lamination.

greets:
Tyimo
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Old 30th November 2012, 07:04 AM   #18
JZatopa is offline JZatopa  United States
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Could you compare the sound of these transformer to any others you have used?
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Old 30th November 2012, 12:21 PM   #19
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Hello to Hungary!
Are you living in Budapest?
If so, all I can tell you is that it's the place with the most gorgeous women I have ever seen in my life. You're really lucky living in this place :-)
Regarding the cores, 0.1mm is not so easy to find. Ask your vendor for 0.23-0.30mm, most likely he has also 0.1mm, even in special order only.
Personally I can find even 0.05mm but it is very hard to acquire in smaller quantities. India and Chine are the best place to search.
Have a nice day.
PS: personally I buy my own ones as a special order to a factory in far east, they are willing to manufacture them for me because I have had a very good cooperation in the past and they now help me to survive because here in Greece everything dies. They do not manufacture 0.1mm cores but only as a special order 1-2 times per year.
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Old 30th November 2012, 01:01 PM   #20
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Quote:
Originally Posted by DJNUBZ View Post
Could you compare the sound of these transformer to any others you have used?
Greetings to Chicago!
Thanks for your message.

I will write you in more detail and will try to be focused in details as much as I can.

These cores are practically left-overs of a huge project that is now under completion. Next week I will post some pictures for all of you. These were proposed for transformer volume control (TVC) but we decided that this will be placed externally, not inside the mono amps but at an earlier degree, like a passive preamp.

There are many aspects that contribute to the sound that these trannies are able to give. This is the angle from which they must be observed. They are not a commercial product, made by a company which makes is living out of selling transformers, it is not possible to establish a company and live by selling them, their cost would be sky-high. They are made with only one scope in mind: to give something extraordinarily good, something that is not possible to acquire even on a special order but only if paying many thousands of dollars. They are made to give out the best that can be done, without the slightest compromise that deteriorates their sound.

The structure of the secondary is incredibly complex, remember, they are 32 leads coming out of each of the formers! Manufacture is very painful and costly, so the expectations are not only high, but the absolutely highest possible.

So let's come to their sound, after this small introduction...

They do not give out this lush, lazy and uninvolving sound that many people here mistakingly seek for. They are extremely transparent, dynamic, incredibly immediate, with razor-sharp detail & focus. All things shrink to their original dimensions, with more defined focus and boundaries and at the same time ambient becomes larger, more air and depth. Both at the same time! You will notice a unique layering of things in space, never listened before and at the same time incredibly defined distances between each layer.

I have listened to practically all OPTs from commercial vendors. Needless to write that nothing comes close. Absolutely nothing. I have also listened to several DIY transformers, most of them surpass the level of performance of commercial products. These were the benchmark against which the comparisons were done. There are several things here that are met for first time. One is the incredibly high number of primary turns for such a design, this way you can lower the magnetic gap and achieve very high primary inductance, which leads to very high effective permeability of iron core, which leads to all the goods found on earth, and at the same time you can have a lot of power available, something that is not met with permalloy cores. Permalloy behaves very nicely (not necessarily better) but only in a very small margin of core excitation, outside of which sound is far worse than what those transformers provide. The second is the p-s insulation, it is so unique with so subjectively unique sound that is hard to believe. There are resons for this kind of performance but it is outside of the scope of this article.

Other aspects contribute to their level of performance as well. There are no ferromagnetic pieces around, except the corner feet, which can be replaced easily (they are far away from the core anyway...). Banding strap is of highest quality feasible, mounting brackets are made of CNC cut baltic birch plywood and last, there is intentionally no cover at all. I can manufacture two nicely looking covers out of wood or corian but any metallic material is intentionally avoided.

Apart from what described, overall, you get more tonal colors, more inner detail, more finesse and texture portrayal, complexity, dynamics and immediacy never listened before. The end result is to get closer to the performance, feeling the thrill and excitement of the recorded event like never before. All these come as expression of their specifications and not as a result of any snake oil or magic filter. I have studied mechanical engineering and have a working experience of 16 years in the field of magnetics/electronagnetism. I am not making my living out of this, although I am handling several Hi Fi projects right now.

I just wanted to show what can be made if you raise the bar of performance and characteristics as much as possible, outside of any commercial point of view. Here only absolutely highest quality matters and this is the point of view that those transformers must be observed from.

Thank you for reading through.

Regards,
Peter

Last edited by petavgeris; 30th November 2012 at 01:07 PM.
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