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Old 1st March 2011, 04:17 AM   #11
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The foil sticking out of the coils as shown seems to indicate the intended use for driving a low low Z ribbon load...

The WW mag article is from the late 50s early 60s, iirc.

You don't have to do that much in the transformer, since ur covering a very very small frequency range, like what, two octaves or slightly more?? The core can be pretty small as well, and there is no DC to handle. You just need one heck of a step down with the secondary able to handle current, but then the issue is one of obtaining good coupling, since yr secondary will have few turns...

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Old 3rd March 2011, 09:19 AM   #12
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I think that when we want to consider the maximum power ribbon tweeter, we must always bear in mind the extremely high current that flows through a thin strip at any time. Conclusion would be that such a track is very sensitive to any excess electricity, which is logically prior to appearing on the lower frequencies. It is therefore essential, especially at lower cutting frequency crossover, that this cut must be very steep, which is obviously o.e. like RAAL all the time recommend the 4 order crossover for the recommended power, also with logically slightly larger transformer...

What you think about idea to winding secondary coil maybe with litz (stranded) wire to avoid eddy current in transformer?
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Old 4th March 2011, 07:01 PM   #13
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My limited understanding is that the use of foil windings for the secondary is to maximize the coupling between the primary and secondary due to the very small number of turns of the secondary (one has to keep the DCR low).

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Old 5th March 2011, 11:19 AM   #14
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Yes, low DC resistance. It is easy to try, Iwill see.
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Old 5th March 2011, 01:52 PM   #15
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that why you should notice that the interleaving winded inductor Gaedtke shows, have secondaries layers paralelled, and primary layers in series
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Old 5th March 2011, 10:24 PM   #16
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AMCC = Amorphous Metal C-Cores are a good choice for high-end ribbon set-up transformers. The Hitachi Metglas product family available from US companies like ELNA magnetics is the industry standard, and these AMCC cores have been cloned by many China manufactures.

Amorphous metal C-cores allow for operation at higher frequencies at the same flux level. Where traditional steel cores need to operate at increasingly lower flux densities as the frequency increases, which creates distortion.

Some RAAL ribbons use the AMCC-4 size C-core.

http://www.metglas.com/downloads/powerlite.pdf

The RAAL literature mentions that the inductance of the transformer primary winding is designed to be used as a LR slope 1,600Hz crossover element.


Powerlite offers an amorphous metal toroid core with a small slit cut to reduce inductance and help high frequency operation.
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Old 5th March 2011, 11:28 PM   #17
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I dont remember exactly, but is there something about amorphous core take less power to saturate ?
but 'free' of bass frequency maybe no issue

I suspect it would make sense to wind two seperate inductors, and couple them series/paralel
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Old 6th March 2011, 09:12 PM   #18
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Hello everyone, it has been a while since i have been able to do any posting.
I have been working on my studio so I haven't been working on my diyaudio stuff latley.

But may I suggest using a torrid power transformer like some of us have used on our ESL's but in reverse.

My transformer has to 120v primary's and I hooked one to the amp and the other to a fullrange speaker and found very hardly if any degradation in sound quality.

Here you have primary wind that is already designed for 120v at 60hz so it lowest frequency saturation now becomes 15hz at 30v.

And every time you double the input frequency you effectively double the power handling of the transfromer.

For an example, A 50 watt core at 60hz becomes a 400 watt core at 480hz ,or, an 800 watt core at 960hz (suggested crossover frequencies) and so on.

By going stepdown you won't experience any of the problems we have while stepping up for an ESL.
You can easliy add your own secondary winding of heavy gauge wire to a transformation ratio of your choice.

more can be found here ,Step-up transformer design

These cores (at least mine) exhibit a ruler flat response up to and well above (in some cases) 100khz.


p.s. I had promised to finish that study for everyone,so when I get my studio and lab bench back in order I will resume. Thanks ,jer.

Last edited by geraldfryjr; 6th March 2011 at 09:17 PM.
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Old 6th March 2011, 09:23 PM   #19
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I have some magnets that I am planning on building a couple of small ribbon tweeters with and will go the toriod power transformer route as well. jer
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Old 7th March 2011, 12:27 AM   #20
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Ur missing the part where the DCR of the secondary becomes many times that of the ribbon.
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