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Old 9th October 2013, 11:19 PM   #11
X83 is offline X83  United States
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I believe that having some O-core toroids custom manufactured will be the best option in my opinion and the expense will be slightly higher with a longer wait time.

You're correct saying the AnTek AN-1212 or AN-2215 toroids would have to be used in a four core setup to get that higher ratio.

Would you happen to have a diagram, picture or description of how these 230/6V toroidal transformers are wire wound and would it be possible to shorten the 6V section to increase the ratio or rewire the 6V section to lower the overall ratio?
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File Type: jpg O Core Toroidal.jpg (78.7 KB, 203 views)
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Old 10th October 2013, 12:02 AM   #12
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No I don't have a diagram as to how they are wound,
I have never had one to take apart and examine either so I can't even explain it for you, sorry.

Yes, you can shorten the LV winding providing you can get the tape off and get to it, as this will take some time because they use a lot of it.

Or you can just add your own winding as I have done here instead,

Step-up transformer design

Just remember when you shorten the LV winding you must assure that you use a higher cross over frequency in order to not go into the saturation range of your core.
I explain all of that in the above thread.

For an example here is the saturation vs turns chart I made for the 210watt cores I am currently using,

Step-up transformer design

I was looking at the O cores for a bit, at the time I couldn't justify their extra cost but they would make for a nicer time trying to hand wind one.

I don't remember exactly how much of a performance difference they offer, but if I recall it wasn't much.
That was a few years ago and things may have changed quite a bit since then.

If there was anything that I would consider spending more for would be a higher quality material.
Although today's iron is of a decent quality, and, it is much much better than what is found in the EI transformers of yesteryear!!!

jer

Last edited by geraldfryjr; 10th October 2013 at 12:16 AM.
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Old 10th October 2013, 01:39 AM   #13
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Here is some interesting info and links I found about core materials.

Anyone heard of radiometal for transformer core?

The main paper I found the most interesting about core materials can be found here as the link I posted is now broken,

http://cinemag.biz/application_notes/PDF/AN-104.pdf

While I was searching for that thread I had found many more on the subject of core materials and types.

FWIW

jer
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Old 12th October 2013, 07:25 AM   #14
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Quote:
Originally Posted by geraldfryjr View Post
Here is some interesting info and links I found about core materials.

Anyone heard of radiometal for transformer core?

The main paper I found the most interesting about core materials can be found here as the link I posted is now broken,

http://cinemag.biz/application_notes/PDF/AN-104.pdf

While I was searching for that thread I had found many more on the subject of core materials and types.

FWIW

jer
For esl transformers the best materials are HiB (or also called M0) Silicium-iron. They have high operation flux 1,8-1,88 T and very good initial permeability.

I used for my 1:125 full-range esl transformer such cores.
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Old 16th October 2013, 10:49 PM   #15
JonFo is offline JonFo  United States
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Originally Posted by X83 View Post
[COLOR=black]I'm searching for some toroidal type step up transformers with a 50:1 ratio to use with Martin Logan Monolith-III ESL panels ...
.
Joining this thread because I too have MartinLogan Monolith III's and am considering an update to the HV boards and more importantly, the Audio step up transformer.

I have no cost constraints, so would like to know what is the best option. So if the amplimo's (even a pair per speaker) are the best, would love to hear opinions.

X83, I gather you run an active crossover on your speakers, right?

Mine are all active and directly driven by my Sanders ESL amp.
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Old 17th October 2013, 03:47 AM   #16
X83 is offline X83  United States
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I'm currently using an analog active crossover set around 150-180 Hz with the -24db Linkwitz/Riley filter with an Audyssey XT32 calibration system. As you know the ML Monolith-III speakers are rated for 80-250 watts per channel with 500-watts max. Your Sanders ESL amplifier could easily overpower a single 80-watt Piltron ESL transformer so the best option might be to use more than one or find something better with a higher VA or wattage rating. After all the stock ML EI-core ESL transformers are the electrical fulcrum point between your amplifier and the stator panels.

I've been doing a lot of research and found that the grain oriented silicon steel type OA-core toroidal step-up transformers seem to be the best solution. The steel strip construction ensures that the grain boundaries are optimally aligned, improving the transformer's efficiency by reducing the core's reluctance. Since O-Core toroids have no sharp edges, they have a higher kV dielectric rating and require less insulation which can be wound with less fill factor resulting in a lighter & smaller transformer than the conventional box section toroidal cores. The more popular Antek or MultiComp VTX 230/6V 50VA power toroids only have an 84% efficiency rating while the silicon steel OA-Cores with a greater VA rating are capable of 96% to 99% efficiency. My plan is to have some 300VA to 800VA OA-Core toroids custom built with a 1:25 or 1:30 ratio to be used in pairs for each stator section. I may purchase a few of the toroidal OA-cores just wound entirely with a single secondary section and wind the primaries myself. I might be able to wind the primaries using some Litz flat braided wire or flat Laminax which is frequently used for toroidal transformers with higher step up ratios wound concentrically to cover the entire surface of the core just for testing purposes.
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Old 17th October 2013, 07:00 AM   #17
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Thick insulation layers are desired especially closest to the core, and winding's alike.

This helps to reduce the overall parasitic (extra) capacitance of the transformer.

If you plan on winding it yourself consider voltage safety range of at least 12kv to 20kv or more on single core.

The Antek I tested failed at 4.5kv peak (due to the integral electrostatic shield) and when using two cores the overall voltage to the panel would be about 9kv peak or more at high levels at a 1:80 transformation ratio.

As I have mentioned before I was able to get as much as 20Kv-25KV peak out of the two cores that I am using and they are better insulated than the Antek's are.
Even before I had removed the extra 4 winding's that were on it that I didn't need.

Remember that the VA ratings are typically rated at 50Hz and it is capable of much more at higher frequency's providing that the winding's can handle the current.

Therefore if you double the input frequency then you can double the input voltage and this results in a VA capability of the core of 4 times higher.
If you triple the frequency and voltage then the VA capability would then be 9 times more and so on as ohms law says V^2/R=R.

Do try to use the largest core that you can afford as this will help keep the total amount of turns to a minimum as well as the capacitance to an extent.

This will also give you more room to have the HV winding kept to a single layer without any overlapping turns thus reducing the chance of flashover between adjacent turns and greatly reduces the inter winding capacitance.

Besides the benefit of the large core will allow for a lower design frequency as well, if planned out properly.

For a 1:50 ratio this is very possible with a 1800VA (or larger)rated core but for say 1:100 to 1:150 2 to 4 layers for the Hv winding may still be necessary depending on the gauge of wire you choose.
Again, Double or triple up or more on the insulation thickness between the layers as much as you can, too reduce the interwinding capacitance as well.

I used the dimensions from Alpha core to do my calculations and started writing a program to help me with them but I have not finished it yet

Due to winding current reasons I think that 30ga. is ample to keep from fusing the wire if a flashover should occur within the panel itself.
I wouldn't go any less the 32ga. or so by the calculations I have done so far unless you don't mind rewinding 1000 to 3000 turns of fine wire all over again!!

FWIW

jer
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Old 17th October 2013, 11:42 PM   #18
X83 is offline X83  United States
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Originally Posted by JonFo View Post
I have no cost constraints, so would like to know what is the best option. So if the amplimo's (even a pair per speaker) are the best, would love to hear opinions.

In my search for a better ESL toroidal with a higher wattage rating, I was able to contact Ir. Menno van der Veen in Netherlands who is the engineer of the Pliitron transformers which are manufactured by company called Amplimo. Ross Whitney from Plitron told me they could custom design an ESL toroidal transformer specifically for this application that would necessitate a non-recurring engineering charge of $1000 US which does not include the price of the transformers themselves. I was also able to get some more information about the existing Amplimo ESL toroidal transformers along with their price list.

ST105PP cost EUR 217.80 (incl.21% VAT)
ST106PP cost EUR 272.25 (incl.21% VAT)

http://www.mennovanderveen.nl/
http://www.amplimo.com/
http://www.plitron.com/
.
Attached Files
File Type: pdf Amplimo ST105.pdf (131.4 KB, 18 views)
File Type: pdf Amplimo ST106.pdf (136.0 KB, 19 views)
File Type: pdf Amplimo ST105PP specs.pdf (70.0 KB, 18 views)
File Type: pdf Amplimo ST106PP specs.pdf (69.6 KB, 11 views)
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Old 18th October 2013, 01:23 AM   #19
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Quote:
Originally Posted by JonFo View Post
Joining this thread because I too have MartinLogan Monolith III's and am considering an update to the HV boards and more importantly, the Audio step up transformer.

I have no cost constraints, so would like to know what is the best option. So if the amplimo's (even a pair per speaker) are the best, would love to hear opinions.

X83, I gather you run an active crossover on your speakers, right?

Mine are all active and directly driven by my Sanders ESL amp.
You have an audio step up transformer and direct-drive Sanders ESL amp. Does your direct-drive high-voltage amp need a step-up?

Ben
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Old 18th October 2013, 03:09 AM   #20
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Originally Posted by bentoronto View Post
You have an audio step up transformer and direct-drive Sanders ESL amp. Does your direct-drive high-voltage amp need a step-up?
I'm guessing the Sanders ESL amp mentioned by JonFo is not a HV direct-drive amp.
Rather it is the current Sanders amplifier designed to drive the difficult load impedance that most ESLs with step-up transformers exhibit.
Sanders Sound Systems ESL Mark II Amplifier

Last edited by bolserst; 18th October 2013 at 03:12 AM.
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