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Old 31st December 2012, 05:19 PM   #31
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Location: Jackson,michigan
Yes, this is correct.

At the time I had done this study I had little knowledge of transformers other than different core material types and transformation ratios.
The effects of Leakage inductance and self capacitance was new ground for me.
Also the importance of the load resistance I was aware of but didn't realize how much it meant under certain conditions.
This I learned more about as I dug deeper into the situation.

My findings are such that the core size and number of primary turns determines the lowest frequency of operation as per peak input voltage and is true for all transformers.

And the self capacitance along with the leakage inductance determines the resonate frequency of the transformer and you want to stay away from that range although added some resistance to dampen this resonance is common practice.

I have not gotten in to core losses of the materials at high frequency's yet.
But, I do know that the name of the game these days is to have better efficiency.
It is known that better core materials are used these days compared to that of yesteryear.

However amongest my extensive search's I find it difficult to find exactly what percentages of the materials are actually being used and for which product for any particular company.

This is where us as DIYer's are left at our mercy.
Unless one decides to buy a particular core material of known parameters at a higher cost (aside from the increased cost due to the bad economy and the fact that buying in volume is cheaper).

The B-H curves that I got from the typical cores that I have laying around where much better and straighter in the Toroid's than some of the E-I that I have from even back as far as the early 80's.
Although not the greatest compared to some more exotic materal's.

Step-up transformer design

As for as using a load I did some tests with and without a load and I did use a load using the transformer in a 1:1 transformation ratio frequency response test using just the to 120v windings,If I remember correctly.

In that test I used a resistor and I also used a my little two way sony speaker.
In the tests showing the flat response I was using a resistor as a load for the scope and sweep test pictures.

When I hooked up the speaker I found very little difference if any in the quality of sound with or without the transformer in the circuit.
Being that the windings were for 120v at 60Hz I shouldn't have any core saturation problems getting to 20hz at 30v rms.

Listening to some music the only thing I noticed was a subtle increase of muddiness and distortions in the extreme low end.
But, It wasn't that bad to call it terrible it just sound loser and above about 200hz every thing sounded as clean and crisp as the tests without the transformer.
This was when I deemed that this transformer might work very well for my ESL's and it did.

I also did a quick test of ultrasonic's with the ESL setup and found it worked as well up to about 50KHZ or so and was enough to catch the barking dogs next door's attention!!!
The limit's of my microphone caused me not to get any real accurate measurements at the time.
But, Hey, I least I got them to stop barking every time I beamed the signal to them out my open window !!! He,he,he,he

So when you talk about the cost of audio transformer R&D certainly play's a big part as does the cost of the materials these days.
The bigger the core the more material.

The higher the primary voltages ( and vise versa depending on Step-up or step-down) the more turns are required.
This raises the self capacitance and more measures must be accounted for in order to reduce this effect.
Thus the time it takes to start over and test it again!
Therefore a even bigger core is need to use a thicker winding insulation between the layers to lower the self capacitance.

Another good thing about toroid cores is that they are more efficient and have a lower leakage inductance than the typical E-I.
Not to mention the better materials commonly used these days.
This also helps to reduce there size as well.

Just like the Acoustat's interfaces it takes a lot of iron to make a good fullrange transformer for ESL's

Alpha core has some very large cores that can be used to affordably make such a transformer.
They have some very large cores and also should have enough room to use extra extra thick winding insulation layer's in order to help cut down on the the transformer's self capacitance.

This is a great thing and would be perfect for some large panels but the gain is only small for the small panels that I have been working with. Although it would still be a large improvement.
More on that later.

The last and foremost reason the cost is so high is that the manufacture's have you right were they want you and know that their product is exactly what you are looking for and have very little options other than to by their product!.

I know inflation has caused things to go up considerably, But seriously $400 for one Plitron with only a 90 watt rating?

Even 4 Antek 0506's per panel would cost 1/8 that and give you just as good if not better performance and a higher power rating as well !!!

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Old 31st December 2012, 05:52 PM   #32
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Thanks Jer, I was looking at those Piltrons to $373 seemed a bit high, are the 506's 50va as well?
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Old 31st December 2012, 06:22 PM   #33
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Yes they are, DeltaStar.

I have not used them as of yet,But many have and use just two of them.
I would suggest to use 4 of them as I mentioned earlier as this would help to lower the saturation frequency point and increase the power handling only this is not really an issue at the higher frequency's.
I don't have a 0506 to test as Bolserst has already done that.
Since the 120v windings are bifillar wound using them in parallel and/or just one per core may reduce the the total transformer capacitance for the system compared to using them in series, on top of increasing the power handling to well over 200 watts for the 4 of them.


Last edited by geraldfryjr; 31st December 2012 at 06:26 PM.
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Old 31st December 2012, 08:25 PM   #34
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Hello DeltaStar,
I use 230V/6V Farnell/Multi-Comp transformers, which are not sold in the US. However, I've also sound-tested a pair of those Antek AN-506's briefly, driving my hybrid ESL's, and they sound great. Another builder here on the forum, dochungwell, has been using the Antek 506's for over a year now I believe and he's quite happy with them.

On my blogpage (link below) there are schematics showing the Antek AN-506's wired up in both tandem and quad configurations. There is also a link on my blog page to Bolserst's test report on the Antek AN506's. In addition, I think Jer will be doing some testing and measurements on the larger Antek AS-1206 soon.

Here's a photo of those 50VA Antek 506's:
Click the image to open in full size.

Last edited by CharlieM; 31st December 2012 at 08:29 PM.
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Old 31st December 2012, 11:12 PM   #35
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Originally Posted by bear View Post
See, that just doesn't make sense because it takes a lot of effort to make a standard audio transformer have a nominally flat response to 60-75kHz. To get one to go all the way to 100kHz or above is extraordinary and doesn't just randomly happen... something is going on here that at least isn't exactly clear to me
I’ll take a stab at describing why simplex wound power toroids provide extended HF response when driving hybrid ESLs, while much effort is needed to do the same in tube amplifiers. It basically boils down to two major differences:
1) ESL step up transformers are driven from low impedance sources while tube amp transformers are driven by relatively high impedances sources.
2) For hybrid ESL use, the required LF bandwidth is limited to 200-300Hz while transformers for tube amplifiers generally need to handle another 2-3 octaves.

These two major differences allow the use of significantly lower number of primary turns, because:
1) Low impedance drive allows the use of much lower primary inductance since the voltage applied to the primary will not be modulated by voltage drop across the source impedance due to current that varies with frequency and load. Low impedance drive results in flat low distortion voltage response applied to the primary of the transformer even with widely varying current from impedance variations and core related loads. For reference, the Antek AN-0506 has a primary inductance of only about 15mH.
2) Since the LF bandwidth is limited to 200-300Hz, lower number of primary turns can be used while retaining adequate power handling before core saturation.

Reducing primary turns is very beneficial as leakage inductance is proportional to number of primary turns squared. So reducing the primary turns results in significant gains in HF bandwidth. Leakage inductance is also inversely proportional to the length of the winding, so longer winding is better. In the case of the toroid, it’s core shape allows a given number of turns to be spread over 4-6 times the length as for an EI core with the same core area. This is why simplex wound toroidal power transformers are useable for ESL step-up but simplex wound EI power transformers are not.

Now I’m not sure about the 100Khz+ bandwidth that was mentioned, I believe that was a test with only a 10 turn primary which significantly reduced the power handling capability. For the Antek AN-0506, the 6V windings have 44 turns and provide enough power handling capability for hybrid ESLs crossed in the 200-300Hz range.
Attachment #1 shows the response using two of the AN-0506 connected as described below driving a 1200pF panel.
With no load, bandwidth was 47kHz.

Just to clarify, you are taking a step down stock power toroidal transformer and feeding the test signal into the 120vac primary and looking at the lower voltage output?? No load?
See Attachment #2 borrowed from Jazzman’s website:
Jazzman's DIY Electrostatic Loudspeaker Page: The Electronics Package

For ESL step-up transformer use, the power toroids are driven in reverse. (ie the low voltage secondaries are used as the input and the 120VAC primaries are used as the output). Most setups use dual 120VAC primary and dual secondary(6VAC) transformers. The four 6VAC windings are connected in parallel and used as the input. The four 120VAC windings are connected in series and used as the output. The result will be step-up ratio of about 75:1 depending on the exact turn ratio used in the power toroids.
Attached Images
File Type: gif Antek_dual.gif (69.1 KB, 211 views)
File Type: jpg Jazzman_Dual Anteks.jpg (223.6 KB, 209 views)

Last edited by bolserst; 31st December 2012 at 11:16 PM.
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Old 1st January 2013, 12:33 AM   #36
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looking at the parts list I noticed the IN4007 diode's, Do they stand up well in this usage? They were in my servostiks and I ended up replacing them with varo v65 which were better.
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Old 1st January 2013, 01:11 AM   #37
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Yes, I use them although I have had a few short on me before from current surges from arcs, but most all of them survived.
Use the ones with a higher current ratings, I think they range from .75 to 1.5 amps.

I have been using them in my HV supply and have yet to blow one out,


Last edited by geraldfryjr; 1st January 2013 at 01:18 AM.
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Old 1st January 2013, 03:37 AM   #38
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Originally Posted by DeltaStar View Post
looking at the parts list I noticed the 1N4007 diode's, Do they stand up well in this usage?
In this circuit they see at most 650V across them which is roughly 2/3 of their rating.
I have never had a problem with 1N4007 diodes working at this voltage oldest ESL in regular use is 18 years old.
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Old 1st January 2013, 12:06 PM   #39
tyu is offline tyu  United States
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There A lot of repeat on this info.....thanks for geting the 1k diodes useg out there one more time.... thay work great an can be had at the rat-shak any time in the US...
I have seen the Trodel in the ML summit an it look just like one of the Antek AN-506's same size an wate...thay do use an crossover in the primary centap...this may give a edg
happy new year
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Old 10th January 2013, 02:01 PM   #40
tyu is offline tyu  United States
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Has anyone done test with Antek Tranfourmers with a passive crossover are any crossover in line??....say sets at 250-300hz upslop??...
Or are these test done full rang.
I know this may have been ask alredy...some where...
Thanks for any an all info on ESLs
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