My first ESL build, and I am trying to decide on the correct transformer.
From what I have read on the forums, a toriod is the way to go for a hybrid.
I have been looking for a 230v 2x6 transformer with no real luck.
It has been suggested that the Antek AN-0509 works great, but it says discontinued on their website.
Could anyone recommend a different transformer?
Also, my panels are curved, 12"x40" (30x100 cm), 1mm front & 1.1mm back spacing. I have no way to measure, but I estimate 1.4nf panels..... Does this sound about right?
I'm thinking my curved panels have to much curve to them. What would be the theoretical limit on a curved panel. My panels are currently 30 arc.
Any insight to the above questions is much appreciated.
Thanks
From what I have read on the forums, a toriod is the way to go for a hybrid.
I have been looking for a 230v 2x6 transformer with no real luck.
It has been suggested that the Antek AN-0509 works great, but it says discontinued on their website.
Could anyone recommend a different transformer?
Also, my panels are curved, 12"x40" (30x100 cm), 1mm front & 1.1mm back spacing. I have no way to measure, but I estimate 1.4nf panels..... Does this sound about right?
I'm thinking my curved panels have to much curve to them. What would be the theoretical limit on a curved panel. My panels are currently 30 arc.
Any insight to the above questions is much appreciated.
Thanks
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Hi,
Toroids ar just one way to go. It can also be the way in many cases, but there are always other options.
There have been many comments about which toroids might be useable and which may not be useable. I still prefer the single primary, single secondary versions, as they are really "idiot proof" regarding internal flashover issues.
1.4nF sounds reasonable for a panel of the given dimensions.
30°, or +-15° is ok. More than that and tensioning of the diaphragm and mounting it correctly becomes increasingly difficult.
jauu
Calvin
Toroids ar just one way to go. It can also be the way in many cases, but there are always other options.
There have been many comments about which toroids might be useable and which may not be useable. I still prefer the single primary, single secondary versions, as they are really "idiot proof" regarding internal flashover issues.
1.4nF sounds reasonable for a panel of the given dimensions.
30°, or +-15° is ok. More than that and tensioning of the diaphragm and mounting it correctly becomes increasingly difficult.
jauu
Calvin
I'm using tandem Multicomp/Farnell 50VA 230V/2x6V toroids purchased from Newark in my esl's and they are fantastic. At Newark, the Farnells have been replaced by VTX brand, with same part number as THESE
I would to with the VTX's above. At least the high voltage side (most prone to flashover) is a single winding. Besides, the chances of finding single-primary/single-seconary trannies available for shipment to the US is practically zero.
I would to with the VTX's above. At least the high voltage side (most prone to flashover) is a single winding. Besides, the chances of finding single-primary/single-seconary trannies available for shipment to the US is practically zero.
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Calvin/Charlie, thanks for all the information you have provided.
I have another question that I am hoping you can answer.
I was looking at the Antek site, and even though the AN-0509 are discontinued, they have the AS-0509 which is stated as Audio grade.
Now, I am a newbie at this, but would'nt these work too?
From what I read the AS versions has a shielding, so maybe this sheilding would be prone to arcing?
I have another question that I am hoping you can answer.
I was looking at the Antek site, and even though the AN-0509 are discontinued, they have the AS-0509 which is stated as Audio grade.
Now, I am a newbie at this, but would'nt these work too?
From what I read the AS versions has a shielding, so maybe this sheilding would be prone to arcing?
The AN series is the non-shielded version which works better in reverse as a step up transformer and the AS series is the EMI shielded version which are more prone to short out with higher voltage use. Also the 0509 toroid is a 9V unit and I believe most people are opting for the 230/6V ratio for most ESL applications.
Which company are you referring too?
Typically they charge a lot for just a few pieces and you would need to commit to a large batch in order to make it cost worthy.
I have not yet inquired about such costs yet as I am just now understanding on what values to start with.
I would start with the largest core that you could afford and shoot for a primary impedance of about 8 to 32 ohms or so at your lowest frequency of operation.
This will help keep the amp happy without too many complications and losses of having such a large amount of total turns involved.
Your common 240v/6v X 2 power toroids that we are using now (at a 1:80 step-up ratio) will allow for operation of about 300hz to 360hz with 40Vrms of input voltage.
The impedance of such a setup is in the order of about 2 ohms or less at that frequency.
Keeping your crossover frequency above about 400hz to 600hz will greatly help to keep your amp from going into the danger zone, especially if you like to crank it up a bit.
Thus in order to raise this impedance to a safer level at that frequency (or lower), it would require about 2 to 6 times the amount of turns found on one of the smaller cores that many have been using.
Increasing the amount of total turns also raises the parasitic capacitance of the transformer and this is not good.
Thus using a larger core will allow for your transformer design to have a higher impedance at the lower frequency's that is safer for the amp using around the same amount turns to as much as 4X of total turns while not raising the transformers parasitic capacitance as much.
You want to limit your HV winding's to single layers with no winding overlap!! And with lots of insulation in between the layers as well.
This will greatly help to keep the transformers capacitance to a minimum.
I have covered this in many threads already but if you have any questions about this, Please do ask!!
It is a little hard to grasp at first but with time you will find that it is not at all a mystery of how the transformers work, although there is much more involved than just the transformation ratio.
Alpha Core has some very good prices on some very large quality raw cores to work with.
Silicon Steel Toroidal Cores - In Stock
It is very possible to hand wind such a transformer using a large core like the #140 or #160 or larger and be very cost effective per performance.
It is just tedious to do, and, if you have ever unwound a toriod core then you know what you are in for.
I have been working on this for quite sometime.
But since this is just a hobby for me I have had a lot of other pressing projects that I have been trying to do as well, sorry for the delays.
Do stay away from the shielded types as warned!!
I have found that they are easily prone for failure and here is a link to those tests using a Antek AS-1206,
A TEST JIG FOR FINDING ESL STEP-UP TRANSFORMER PARAMETERS
The shielding also adds to the transformers self capacitance as well by as much as 80pf to 200pf (as measured on my sample) depending on the overall size of the core.
For example, When I took all of the extra winding's that I didn't need on the cores I am using (a Parts Express Buyout), it dropped my cores self capacitance to one 1/2 to 1/3 of what it was when I first started measuring it in the "step-up transformer design" thread.
Here are the impedance curves for just one core (Antek AN-1206) with no extra panel capacitance added,
http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-6.html#post3404300
When you add two cores together by paralleling the primary winding's this will cut the low frequency impedance in half that is shown on the charts (for an example).
And by tying the HV winding in series like we do this also lowers the high frequency impedance due to the increased transformation ratio.
I believe this measurement was done with the HV windings in series just as they would be used.
Therefore the actual impedance for two cores as they are used would be half of what the chart depicts.
These charts are with just the transformer capacitance alone and adding more from the panel will then lower the High frequency impedance even more.
Here are some photos of when it failed,
http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-6.html#post3404250
Testing Your Transformer and Using the Transformer Test Jig
For more info these threads may be of interest to you as well,
http://www.diyaudio.com/forums/planars-exotics/233008-esl-hybrid.html#post3434477
http://www.diyaudio.com/forums/plan...p-up-measurements-part-1-2-a.html#post2823635
This is the beginning of a very intense study I did on using common toroid power transformers.
It is a very long thread, But it deserves a good read through and may answer a lot of questions you may already have,
http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-2.html#post2099714
FWIW
jer
Typically they charge a lot for just a few pieces and you would need to commit to a large batch in order to make it cost worthy.
I have not yet inquired about such costs yet as I am just now understanding on what values to start with.
I would start with the largest core that you could afford and shoot for a primary impedance of about 8 to 32 ohms or so at your lowest frequency of operation.
This will help keep the amp happy without too many complications and losses of having such a large amount of total turns involved.
Your common 240v/6v X 2 power toroids that we are using now (at a 1:80 step-up ratio) will allow for operation of about 300hz to 360hz with 40Vrms of input voltage.
The impedance of such a setup is in the order of about 2 ohms or less at that frequency.
Keeping your crossover frequency above about 400hz to 600hz will greatly help to keep your amp from going into the danger zone, especially if you like to crank it up a bit.
Thus in order to raise this impedance to a safer level at that frequency (or lower), it would require about 2 to 6 times the amount of turns found on one of the smaller cores that many have been using.
Increasing the amount of total turns also raises the parasitic capacitance of the transformer and this is not good.
Thus using a larger core will allow for your transformer design to have a higher impedance at the lower frequency's that is safer for the amp using around the same amount turns to as much as 4X of total turns while not raising the transformers parasitic capacitance as much.
You want to limit your HV winding's to single layers with no winding overlap!! And with lots of insulation in between the layers as well.
This will greatly help to keep the transformers capacitance to a minimum.
I have covered this in many threads already but if you have any questions about this, Please do ask!!
It is a little hard to grasp at first but with time you will find that it is not at all a mystery of how the transformers work, although there is much more involved than just the transformation ratio.
Alpha Core has some very good prices on some very large quality raw cores to work with.
Silicon Steel Toroidal Cores - In Stock
It is very possible to hand wind such a transformer using a large core like the #140 or #160 or larger and be very cost effective per performance.
It is just tedious to do, and, if you have ever unwound a toriod core then you know what you are in for.
I have been working on this for quite sometime.
But since this is just a hobby for me I have had a lot of other pressing projects that I have been trying to do as well, sorry for the delays.
Do stay away from the shielded types as warned!!
I have found that they are easily prone for failure and here is a link to those tests using a Antek AS-1206,
A TEST JIG FOR FINDING ESL STEP-UP TRANSFORMER PARAMETERS
The shielding also adds to the transformers self capacitance as well by as much as 80pf to 200pf (as measured on my sample) depending on the overall size of the core.
For example, When I took all of the extra winding's that I didn't need on the cores I am using (a Parts Express Buyout), it dropped my cores self capacitance to one 1/2 to 1/3 of what it was when I first started measuring it in the "step-up transformer design" thread.
Here are the impedance curves for just one core (Antek AN-1206) with no extra panel capacitance added,
http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-6.html#post3404300
When you add two cores together by paralleling the primary winding's this will cut the low frequency impedance in half that is shown on the charts (for an example).
And by tying the HV winding in series like we do this also lowers the high frequency impedance due to the increased transformation ratio.
I believe this measurement was done with the HV windings in series just as they would be used.
Therefore the actual impedance for two cores as they are used would be half of what the chart depicts.
These charts are with just the transformer capacitance alone and adding more from the panel will then lower the High frequency impedance even more.
Here are some photos of when it failed,
http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-6.html#post3404250
Testing Your Transformer and Using the Transformer Test Jig
For more info these threads may be of interest to you as well,
http://www.diyaudio.com/forums/planars-exotics/233008-esl-hybrid.html#post3434477
http://www.diyaudio.com/forums/plan...p-up-measurements-part-1-2-a.html#post2823635
This is the beginning of a very intense study I did on using common toroid power transformers.
It is a very long thread, But it deserves a good read through and may answer a lot of questions you may already have,
http://www.diyaudio.com/forums/planars-exotics/161485-step-up-transformer-design-2.html#post2099714
FWIW
jer
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Toroid's are more efficient per size than the IE types.
By as much as 40% to 60%, I forget exactly how much.
EI types are a bit easier to work with as far as winding goes.
However it is difficult to calculate how many windings you can put in the winding space while having a thick insulation between winding layers and alternating them to reduce the capacitance.
Having thick insulation layers keeps the transformers self capacitance to a minimum,But again this is limited to the winding space.
This is a big deal when working with voltages with as much as 5Kv to 10Kv peak (or more).
In the Step-up Tranformer design thread a fellow member designed and built a very nice EI type transformer all hand wound only too later fail due to internal arcing!
I think he attempted this 2 or 3 times, and I haven't seen any other reports since then if he had corrected the issues.
Toroids aren't as limited in this manner.
As there is plenty of room to have thick insulation layers providing you choose a large enough core to work with.
Compared to the EI structured designs it will be about 60% of the size as well.
I believe I have read somewhere that Toroid's exhibit much less leakage inductances.
This means a lot when it comes to keeping the transformers self resonance above the audio passband.
The tape wound fashion of a Toroid core also cuts down on the action of eddy current losses within the core itself.
The most important part is the type of iron and lamination thickness that are commonly available as IE stamping's.
It can be quite expensive to get a quality iron, and, The thinner the laminations are the more the cost goes up, almost exponentially!
It is easier for manufactures to produce tape wound cores than it is to stamp and assemble IE's.
Since today's norm is about efficiency it is common for them to use a good quality iron and thin tape strips for the lamination as all they have to do is roll it up into a doughnut.
Unlike the power IE's of yesteryear with poor quality iron and lamination's that are usually much much thicker such as the MOT's that are still used today.
This is the main reason why good quality HiFi EI transformers for audio use are so expensive.
I have done many tests on the quality of sound of a signal through my common power toroid at 1:1 ratio using the two 120v:120v winding's using just an amp and a speaker and it was quite good!!!
I did this before I tried using it to power my ESL's because of the same question that everybody ask's, "Are They Good Enough to use and is the Sound Quality Good Enough?".
There was just a subtle bit of muddiness on the extreme low end is all.
Even that was barely noticeable and only at a high volume.
This be could improved just by using more iron.
I have concluded this effect to the possibility of the amp having less of dampening affect on the cones movement due to the coupling of the transformer.
I did a study on this which led me to Double, Quad and Hex stacking the cores I was working with.
Providing that the amp could produce a clean square wave, the transformers output produced a very clean square wave as well!!
I was so amazed at this because I have never ever before seen this type of performance out of all of the IE types I had test up to that day including a few Tube OPT's that I have.
I was able to measure the response of the transformer well into the 100's of Khz and as much as into the AM broadcast bands as well.
I regularly see the RF from local radio stations when I am testing them with my scope.
I have never experienced this with a common older EI type designs and core material that they use, at least not into the RF range.
I haven't been able to measure any significant added amount of THD's of the signal as transferred through one of my Toroid Cores except for approaching and well into core saturation as shown here,
A TEST JIG FOR FINDING ESL STEP-UP TRANSFORMER PARAMETERS
In some of the charts you will see some glitch's and irregularities, and those I later have proven to be caused by my motherboards sound system that I was using at the time.
My other sound cards did not do this.
Mostly all of THD the measurements that I did get that were above .1% to .5% were found to be that of my amplifier (Crown DC300a) or caused by the core just as it was going into saturation and that was only about .5% or so.
Therefore the quality of the iron used in today's Toroid Power Cores is very good and the many listening tests (mine as well as others) have proven them to be exceptional as well.
In the cases at above, starting at 600Hz to 1Khz, I wasn't able to measure any added THD's except that of my sound card and amp in the range of .01% to .005% all of the way to 20-25Khz or so.
I believe the limit of my sound card is .005% or so as measured by a calibrated loopback test.
I will do more on this sometime once I get every thing set back up again since all of my issues to stopping were from breakdowns of pushing the voltages as far as I could get them as I have already explained.
Under normal operation it is just the clearest and cleanest thing I have ever heard in my life.
Pretty darn good for some common ole' Power Toroid's.
I hope this helps you.
jer
By as much as 40% to 60%, I forget exactly how much.
EI types are a bit easier to work with as far as winding goes.
However it is difficult to calculate how many windings you can put in the winding space while having a thick insulation between winding layers and alternating them to reduce the capacitance.
Having thick insulation layers keeps the transformers self capacitance to a minimum,But again this is limited to the winding space.
This is a big deal when working with voltages with as much as 5Kv to 10Kv peak (or more).
In the Step-up Tranformer design thread a fellow member designed and built a very nice EI type transformer all hand wound only too later fail due to internal arcing!
I think he attempted this 2 or 3 times, and I haven't seen any other reports since then if he had corrected the issues.
Toroids aren't as limited in this manner.
As there is plenty of room to have thick insulation layers providing you choose a large enough core to work with.
Compared to the EI structured designs it will be about 60% of the size as well.
I believe I have read somewhere that Toroid's exhibit much less leakage inductances.
This means a lot when it comes to keeping the transformers self resonance above the audio passband.
The tape wound fashion of a Toroid core also cuts down on the action of eddy current losses within the core itself.
The most important part is the type of iron and lamination thickness that are commonly available as IE stamping's.
It can be quite expensive to get a quality iron, and, The thinner the laminations are the more the cost goes up, almost exponentially!
It is easier for manufactures to produce tape wound cores than it is to stamp and assemble IE's.
Since today's norm is about efficiency it is common for them to use a good quality iron and thin tape strips for the lamination as all they have to do is roll it up into a doughnut.
Unlike the power IE's of yesteryear with poor quality iron and lamination's that are usually much much thicker such as the MOT's that are still used today.
This is the main reason why good quality HiFi EI transformers for audio use are so expensive.
I have done many tests on the quality of sound of a signal through my common power toroid at 1:1 ratio using the two 120v:120v winding's using just an amp and a speaker and it was quite good!!!
I did this before I tried using it to power my ESL's because of the same question that everybody ask's, "Are They Good Enough to use and is the Sound Quality Good Enough?".
There was just a subtle bit of muddiness on the extreme low end is all.
Even that was barely noticeable and only at a high volume.
This be could improved just by using more iron.
I have concluded this effect to the possibility of the amp having less of dampening affect on the cones movement due to the coupling of the transformer.
I did a study on this which led me to Double, Quad and Hex stacking the cores I was working with.
Providing that the amp could produce a clean square wave, the transformers output produced a very clean square wave as well!!
I was so amazed at this because I have never ever before seen this type of performance out of all of the IE types I had test up to that day including a few Tube OPT's that I have.
I was able to measure the response of the transformer well into the 100's of Khz and as much as into the AM broadcast bands as well.
I regularly see the RF from local radio stations when I am testing them with my scope.
I have never experienced this with a common older EI type designs and core material that they use, at least not into the RF range.
I haven't been able to measure any significant added amount of THD's of the signal as transferred through one of my Toroid Cores except for approaching and well into core saturation as shown here,
A TEST JIG FOR FINDING ESL STEP-UP TRANSFORMER PARAMETERS
In some of the charts you will see some glitch's and irregularities, and those I later have proven to be caused by my motherboards sound system that I was using at the time.
My other sound cards did not do this.
Mostly all of THD the measurements that I did get that were above .1% to .5% were found to be that of my amplifier (Crown DC300a) or caused by the core just as it was going into saturation and that was only about .5% or so.
Therefore the quality of the iron used in today's Toroid Power Cores is very good and the many listening tests (mine as well as others) have proven them to be exceptional as well.
In the cases at above, starting at 600Hz to 1Khz, I wasn't able to measure any added THD's except that of my sound card and amp in the range of .01% to .005% all of the way to 20-25Khz or so.
I believe the limit of my sound card is .005% or so as measured by a calibrated loopback test.
I will do more on this sometime once I get every thing set back up again since all of my issues to stopping were from breakdowns of pushing the voltages as far as I could get them as I have already explained.
Under normal operation it is just the clearest and cleanest thing I have ever heard in my life.
Pretty darn good for some common ole' Power Toroid's.
I hope this helps you.
jer
Hi All
I can add some observations regarding commercial tororoidal power transformers...
First: Small toroids down to at least 15 VA, perhaps lower, make good ESL transformers. If you dont have ready access to low cost specialist ESL transformers, they are a good option.
Second: For a given secondary voltage rating (e.g. 6 Vrms at 50 Hz), smaller cores have higher inductance and therefore lower distortion.
Third: the bandwidth of the transformer depends on winding capacitance, leakage inductance and the capacitive load. Large cores have higher capacitance and lower leakage inductance (small cores have higher leakage inductance and lower capacitance.) In my experience, the unloaded bandwidth of small cores tends to be a bit higher (15 VA ==> 130 kHz) than large cores (160 VA ==> 70 kHz), but the load is a major factor to consider. If you plan to use just two per ESL, more or less any core size will do. If you plan to use up to multiple transformers per ESL to increase input voltage and/or step up ratio you should model the behaviour and select the core to suit to maximise bandwidth.
Fourth: Definitely avoid transformers with twin primaries due to high winding capacitance and tendency for breakdown. Twin secondaries should be connected in parallel to reduce leakage inductance.
Fifth and most important: Choose transformers that comply with the IEC standard (sorry cant remember standard number). They are required to have sufficient insulation between primary and secondary to withstand 4kV dc for 1 minute.
best regards
Rod
I can add some observations regarding commercial tororoidal power transformers...
First: Small toroids down to at least 15 VA, perhaps lower, make good ESL transformers. If you dont have ready access to low cost specialist ESL transformers, they are a good option.
Second: For a given secondary voltage rating (e.g. 6 Vrms at 50 Hz), smaller cores have higher inductance and therefore lower distortion.
Third: the bandwidth of the transformer depends on winding capacitance, leakage inductance and the capacitive load. Large cores have higher capacitance and lower leakage inductance (small cores have higher leakage inductance and lower capacitance.) In my experience, the unloaded bandwidth of small cores tends to be a bit higher (15 VA ==> 130 kHz) than large cores (160 VA ==> 70 kHz), but the load is a major factor to consider. If you plan to use just two per ESL, more or less any core size will do. If you plan to use up to multiple transformers per ESL to increase input voltage and/or step up ratio you should model the behaviour and select the core to suit to maximise bandwidth.
Fourth: Definitely avoid transformers with twin primaries due to high winding capacitance and tendency for breakdown. Twin secondaries should be connected in parallel to reduce leakage inductance.
Fifth and most important: Choose transformers that comply with the IEC standard (sorry cant remember standard number). They are required to have sufficient insulation between primary and secondary to withstand 4kV dc for 1 minute.
best regards
Rod
I went back to the Antek website hoping by some miracle the AN-0506 was back in stock. But it still said "discontinued" in bold red letters like it was taunting me.
Browsing through the website, I cam across the AN-0206. They are smaller 25va transformers, but I was wondering the disadvantages of using 4 of these per speaker?
Thoughts?
Is there something better then these on the Antek site?
Browsing through the website, I cam across the AN-0206. They are smaller 25va transformers, but I was wondering the disadvantages of using 4 of these per speaker?
Thoughts?
Is there something better then these on the Antek site?
Yes, I think that they would work alright.
Keep in mind the above info that Golfnut has provided.
Even though my cores are rated at 200watts each it seems that I do get better THD performance at the lower frequency's just before the saturation point than I did when testing the AS-1206.
But, only very slightly.
I will have more on this at a later time.
As long as your crossover is above 300Hz/360Hz for any size you won't have any issues about this.
I found that I have gotten better results (for the amplifier) from using from using 4 cores with the 120v winding's on each core rather than 2 cores with its 120v winding in series.
This actually gives you a lesser amount of leak inductance than you would with using just 2 cores total.
I am not sure but it also seems logical that the transfomer's capacitance's are effectively in series as well.
When using separate cores this would suggest that it would lower the overall capacitance reflected through the transformation ratio as well.
More on this later too!
The reasoning is that when you have the two separate cores 120v winding's in series you simply add the two leakage inductance's together ( Hence~ Leakage inductance will be 2X ).
Where as if the two winding's are on the same core they share what is called mutual inductance, and, the leakage inductance is goes up as a square of the multiple of the number of turns.
Hence~ If you double the number of turns then the inductance is 4 times that of a single amount of turns if the winding turns are on the same core.
This hold true for the winding's actual inductance as well as the leakage inductance.
So for just one half of the setup, if you use 2 cores then your leakage inductance will be say 2, and, For one core with its two winding in series, it will be twice that at 4, for an example.
The trick is to keep your leakage inductance as low as you can as especially with larger panels (Larger capacitance).
The effect of leakage inductance and the total capacitance (Panel plus the Transformer) determines the resonate frequency of the transformer system.
You want this above the audio band if possible, else it can be dampened using a resistor on the primary side.
This resonance causes a very high peak in the response of the system at this resonate frequency, and, a very low impedance for the amp if it has to produce energy for it.
Literally a shorting action for the amplifier.
You don't want this to happen!!!
I ran into this action in my study (as documented) as it created havoc for my setup from crossover distortions (because the amp could not supply enough current) also the transformer going into (a Tesla action of operation) oscillation and generating High RF Voltages as well.
This caused resistors that I was using to burn up that should not have and a few cheapy DMM's that I was using for measurements rendered burnt and useless as well.
All because of the RF that was generated when the amp could not switch fast enough leaving the transformer ringing at will.
Now to the main part of your question,
Every time you double the input frequency you can double the input voltage into any winding for what ever voltage it is rated at.
This effectively quadruples the power (VA rating) that can be transferred through the core without it going into saturation.
Being that they are designed for 50Hz/60Hz we will use 50Hz for our example because it is the lowest frequency that can be used for its designed winding voltages (in our case 6V).
So, lets say we use a crossover frequency of 400Hz.
The highest voltage we can apply to our 6V winding will be 48V because 400Hz/50Hz=8 so 8*6V= 48V.
Typically an amplifier that can produce 48V is quite a large amplifier up into the 288 watt range for an 8 ohm rating.
Can our transformer handle this?
The Antek AN-0206 is rated at 25 watts at 50hz and we are doubling are input voltage 3 times.
Every time we double it our VA rating goes up by 2^2 or 4!!
Therefore (4^3times)*25watts= 1600watts!!!
The transformer core would definite be able to handle our 288watt amplifier much less a 100watt one with no problem.
This is providing that the winding's have a thick enough gauge of wire to handle the current.
This should not be much of issue since you plan on using 4 of them and the 6V winding's will be all paralleled together.
Much less than tolerating any SPL's at above 20V to 30V into the step-up transformers with a large panel for an example.
I hope this helps !!!
jer
Keep in mind the above info that Golfnut has provided.
Even though my cores are rated at 200watts each it seems that I do get better THD performance at the lower frequency's just before the saturation point than I did when testing the AS-1206.
But, only very slightly.
I will have more on this at a later time.
As long as your crossover is above 300Hz/360Hz for any size you won't have any issues about this.
I found that I have gotten better results (for the amplifier) from using from using 4 cores with the 120v winding's on each core rather than 2 cores with its 120v winding in series.
This actually gives you a lesser amount of leak inductance than you would with using just 2 cores total.
I am not sure but it also seems logical that the transfomer's capacitance's are effectively in series as well.
When using separate cores this would suggest that it would lower the overall capacitance reflected through the transformation ratio as well.
More on this later too!
The reasoning is that when you have the two separate cores 120v winding's in series you simply add the two leakage inductance's together ( Hence~ Leakage inductance will be 2X ).
Where as if the two winding's are on the same core they share what is called mutual inductance, and, the leakage inductance is goes up as a square of the multiple of the number of turns.
Hence~ If you double the number of turns then the inductance is 4 times that of a single amount of turns if the winding turns are on the same core.
This hold true for the winding's actual inductance as well as the leakage inductance.
So for just one half of the setup, if you use 2 cores then your leakage inductance will be say 2, and, For one core with its two winding in series, it will be twice that at 4, for an example.
The trick is to keep your leakage inductance as low as you can as especially with larger panels (Larger capacitance).
The effect of leakage inductance and the total capacitance (Panel plus the Transformer) determines the resonate frequency of the transformer system.
You want this above the audio band if possible, else it can be dampened using a resistor on the primary side.
This resonance causes a very high peak in the response of the system at this resonate frequency, and, a very low impedance for the amp if it has to produce energy for it.
Literally a shorting action for the amplifier.
You don't want this to happen!!!
I ran into this action in my study (as documented) as it created havoc for my setup from crossover distortions (because the amp could not supply enough current) also the transformer going into (a Tesla action of operation) oscillation and generating High RF Voltages as well.
This caused resistors that I was using to burn up that should not have and a few cheapy DMM's that I was using for measurements rendered burnt and useless as well.
All because of the RF that was generated when the amp could not switch fast enough leaving the transformer ringing at will.
Now to the main part of your question,
Every time you double the input frequency you can double the input voltage into any winding for what ever voltage it is rated at.
This effectively quadruples the power (VA rating) that can be transferred through the core without it going into saturation.
Being that they are designed for 50Hz/60Hz we will use 50Hz for our example because it is the lowest frequency that can be used for its designed winding voltages (in our case 6V).
So, lets say we use a crossover frequency of 400Hz.
The highest voltage we can apply to our 6V winding will be 48V because 400Hz/50Hz=8 so 8*6V= 48V.
Typically an amplifier that can produce 48V is quite a large amplifier up into the 288 watt range for an 8 ohm rating.
Can our transformer handle this?
The Antek AN-0206 is rated at 25 watts at 50hz and we are doubling are input voltage 3 times.
Every time we double it our VA rating goes up by 2^2 or 4!!
Therefore (4^3times)*25watts= 1600watts!!!
The transformer core would definite be able to handle our 288watt amplifier much less a 100watt one with no problem.
This is providing that the winding's have a thick enough gauge of wire to handle the current.
This should not be much of issue since you plan on using 4 of them and the 6V winding's will be all paralleled together.
Much less than tolerating any SPL's at above 20V to 30V into the step-up transformers with a large panel for an example.
I hope this helps !!!
jer
Last edited:
more transformer info
Hi BuyDIY
Because ESLs are voltage driven and draw little current, the power rating of the transformer is not really relevant for ESL applications. From an ESL perspective, the only specs that are important are the step-up ratio, secondary voltage rating, and mains frequency. Equally important are the transformer properties that are not in the spec sheets: leakage inductance and winding capacitance.
Step-up ratio: interpretation is obvious.
Secondary voltage rating and mains frequency: as Jer has explained, the voltage rating is proportional to frequency. So a transformer with secondaries rated for 6Vrms at 50 Hz, can be used at 12 V rms at 100 Hz, etc. If you exceed the voltage on the winding, the transformer core will saturate presenting a low impedance to the amplifier, resulting in high currents and distortion – possibly a dead amp if it’s not protected.
Leakage inductance: comes about from imperfect coupling between two transformer windings on the same core. One or other of the windings will be incompletely coupled to the other and it will appear, from an electronic point of view, to have an extra inductance in series with the winding. This is the leakage inductance, L. Typical values are a few millihenries on the high-voltage side.
Winding capacitance: comes about from three effects (i) capacitance between adjacent turns of the same winding, (ii) capacitance between one of the windings and the transformer core, and (ii) capacitance between the turns of different windings. When you use just two transformers on an ESL in the usual push-pull arrangement, the various capacitances can be treated as a single winding capacitance, C. Typical values are many tens of picofarads, perhaps a few hundred picofarads. The resonant frequency of the transformer is given by fo=1/(2.Pi.sqrt(L.C)) – typically 50 kHz to 130 kHz for toroids. This is the ‘unloaded’ resonant frequency.
When you use the transformer with the ESL, you have to add the ESL capacitance (500pf to 2000 pF) to the winding capacitance. This is the loaded resonant frequency, can easily drop below 20 kHz. The loaded resonant frequency is a good measure of the bandwidth of the transformer-ESL system. You can see why a small leakage inductance is desirable – however, there are compromises – see later). Low inductance is necessary if you want high-step up ratios, higher voltage ratings, lower operating frequencies, or any combination of these.
When you use multiple transformers in an ESL by connecting the high-voltage windings in series and the low voltage windings in parallel. Two things happen: Firstly, the leakage inductances add in series (as Jer surmised). This bit is simple. The way the capacitances behave is more complicated. The capacitances within one winding and between the core and secondary winding appear to add in series (so that capacitance gets smaller.) At the same time all of the capacitances between the two windings add in parallel, so that part gets bigger.
As a result you can connect two or three transformers together without changing the unloaded resonant frequency very much. After that, the resonant frequency falls in proportion to the square root of the number of toroids, but with care you can use up to 8 or 10 toroidal transformers to form a single ‘compound transformer’.
There is a practical upper limit to the VA ratings of the transformers used in ESLs; If you keep the leakage inductance too low with large transformers, the bandwidth of the system becomes limited by the series resistance in the windings.
Also if you have too high a step-up ratio (say 200 for arguments sake), then any inductance in the amplifier output (zero to 10 microhenry depending on design) or the speaker leads (about 1 microhenry), is transformed to the ESL side. If it is 10 microhenry on the low voltage side, then the equivalent inductance on the high voltage side is 10 uH x 200^2 = 400 mH, which is too high.
Hope this is helpful
Rod
Hi BuyDIY
Because ESLs are voltage driven and draw little current, the power rating of the transformer is not really relevant for ESL applications. From an ESL perspective, the only specs that are important are the step-up ratio, secondary voltage rating, and mains frequency. Equally important are the transformer properties that are not in the spec sheets: leakage inductance and winding capacitance.
Step-up ratio: interpretation is obvious.
Secondary voltage rating and mains frequency: as Jer has explained, the voltage rating is proportional to frequency. So a transformer with secondaries rated for 6Vrms at 50 Hz, can be used at 12 V rms at 100 Hz, etc. If you exceed the voltage on the winding, the transformer core will saturate presenting a low impedance to the amplifier, resulting in high currents and distortion – possibly a dead amp if it’s not protected.
Leakage inductance: comes about from imperfect coupling between two transformer windings on the same core. One or other of the windings will be incompletely coupled to the other and it will appear, from an electronic point of view, to have an extra inductance in series with the winding. This is the leakage inductance, L. Typical values are a few millihenries on the high-voltage side.
Winding capacitance: comes about from three effects (i) capacitance between adjacent turns of the same winding, (ii) capacitance between one of the windings and the transformer core, and (ii) capacitance between the turns of different windings. When you use just two transformers on an ESL in the usual push-pull arrangement, the various capacitances can be treated as a single winding capacitance, C. Typical values are many tens of picofarads, perhaps a few hundred picofarads. The resonant frequency of the transformer is given by fo=1/(2.Pi.sqrt(L.C)) – typically 50 kHz to 130 kHz for toroids. This is the ‘unloaded’ resonant frequency.
When you use the transformer with the ESL, you have to add the ESL capacitance (500pf to 2000 pF) to the winding capacitance. This is the loaded resonant frequency, can easily drop below 20 kHz. The loaded resonant frequency is a good measure of the bandwidth of the transformer-ESL system. You can see why a small leakage inductance is desirable – however, there are compromises – see later). Low inductance is necessary if you want high-step up ratios, higher voltage ratings, lower operating frequencies, or any combination of these.
When you use multiple transformers in an ESL by connecting the high-voltage windings in series and the low voltage windings in parallel. Two things happen: Firstly, the leakage inductances add in series (as Jer surmised). This bit is simple. The way the capacitances behave is more complicated. The capacitances within one winding and between the core and secondary winding appear to add in series (so that capacitance gets smaller.) At the same time all of the capacitances between the two windings add in parallel, so that part gets bigger.
As a result you can connect two or three transformers together without changing the unloaded resonant frequency very much. After that, the resonant frequency falls in proportion to the square root of the number of toroids, but with care you can use up to 8 or 10 toroidal transformers to form a single ‘compound transformer’.
There is a practical upper limit to the VA ratings of the transformers used in ESLs; If you keep the leakage inductance too low with large transformers, the bandwidth of the system becomes limited by the series resistance in the windings.
Also if you have too high a step-up ratio (say 200 for arguments sake), then any inductance in the amplifier output (zero to 10 microhenry depending on design) or the speaker leads (about 1 microhenry), is transformed to the ESL side. If it is 10 microhenry on the low voltage side, then the equivalent inductance on the high voltage side is 10 uH x 200^2 = 400 mH, which is too high.
Hope this is helpful
Rod
If you want full or higher power at 300-400Hz you need 0,1mm(or even thinner) core material and not the standerd 0,3mm. Only short time overload is possible.
Yes, I think that they would work alright.
Keep in mind the above info that Golfnut has provided.
Even though my cores are rated at 200watts each it seems that I do get better THD performance at the lower frequency's just before the saturation point than I did when testing the AS-1206.
But, only very slightly.
I will have more on this at a later time.
As long as your crossover is above 300Hz/360Hz for any size you won't have any issues about this.
I found that I have gotten better results (for the amplifier) from using from using 4 cores with the 120v winding's on each core rather than 2 cores with its 120v winding in series.
This actually gives you a lesser amount of leak inductance than you would with using just 2 cores total.
I am not sure but it also seems logical that the transfomer's capacitance's are effectively in series as well.
When using separate cores this would suggest that it would lower the overall capacitance reflected through the transformation ratio as well.
More on this later too!
The reasoning is that when you have the two separate cores 120v winding's in series you simply add the two leakage inductance's together ( Hence~ Leakage inductance will be 2X ).
Where as if the two winding's are on the same core they share what is called mutual inductance, and, the leakage inductance is goes up as a square of the multiple of the number of turns.
Hence~ If you double the number of turns then the inductance is 4 times that of a single amount of turns if the winding turns are on the same core.
This hold true for the winding's actual inductance as well as the leakage inductance.
So for just one half of the setup, if you use 2 cores then your leakage inductance will be say 2, and, For one core with its two winding in series, it will be twice that at 4, for an example.
The trick is to keep your leakage inductance as low as you can as especially with larger panels (Larger capacitance).
The effect of leakage inductance and the total capacitance (Panel plus the Transformer) determines the resonate frequency of the transformer system.
You want this above the audio band if possible, else it can be dampened using a resistor on the primary side.
This resonance causes a very high peak in the response of the system at this resonate frequency, and, a very low impedance for the amp if it has to produce energy for it.
Literally a shorting action for the amplifier.
You don't want this to happen!!!
I ran into this action in my study (as documented) as it created havoc for my setup from crossover distortions (because the amp could not supply enough current) also the transformer going into (a Tesla action of operation) oscillation and generating High RF Voltages as well.
This caused resistors that I was using to burn up that should not have and a few cheapy DMM's that I was using for measurements rendered burnt and useless as well.
All because of the RF that was generated when the amp could not switch fast enough leaving the transformer ringing at will.
Now to the main part of your question,
Every time you double the input frequency you can double the input voltage into any winding for what ever voltage it is rated at.
This effectively quadruples the power (VA rating) that can be transferred through the core without it going into saturation.
Being that they are designed for 50Hz/60Hz we will use 50Hz for our example because it is the lowest frequency that can be used for its designed winding voltages (in our case 6V).
So, lets say we use a crossover frequency of 400Hz.
The highest voltage we can apply to our 6V winding will be 48V because 400Hz/50Hz=8 so 8*6V= 48V.
Typically an amplifier that can produce 48V is quite a large amplifier up into the 288 watt range for an 8 ohm rating.
Can our transformer handle this?
The Antek AN-0206 is rated at 25 watts at 50hz and we are doubling are input voltage 3 times.
Every time we double it our VA rating goes up by 2^2 or 4!!
Therefore (4^3times)*25watts= 1600watts!!!
The transformer core would definite be able to handle our 288watt amplifier much less a 100watt one with no problem.
This is providing that the winding's have a thick enough gauge of wire to handle the current.
This should not be much of issue since you plan on using 4 of them and the 6V winding's will be all paralleled together.
Much less than tolerating any SPL's at above 20V to 30V into the step-up transformers with a large panel for an example.
I hope this helps !!!
jer
Well..... Charlie is right. Finding a transformer in the US, with a single primary and secondary, is next to ZERO.
I think I might go ahead and order the toroids Charlie suggested.
Vigortronix Toroidal Transformer 230V Single Primary 50VA 0-6V 0-6V | Rapid Online
Does anyone see any issues with the above toroids?
If anyone has other suggestions on where I could buy toroids I would like to hear them.
I think I might go ahead and order the toroids Charlie suggested.
Vigortronix Toroidal Transformer 230V Single Primary 50VA 0-6V 0-6V | Rapid Online
Does anyone see any issues with the above toroids?
If anyone has other suggestions on where I could buy toroids I would like to hear them.
Hi,
Could you please explain why? Also, why an audio transformer would need to satisfy continuous max. power rating at those frequencies?
Regards,
Lukas.
Could you please explain why? Also, why an audio transformer would need to satisfy continuous max. power rating at those frequencies?
Regards,
Lukas.
Normal cores are made for 50-60Hz. At these frequencies the core loss is reasonable low (eddycurrents). For high frequencies you need thinner laminations, thats why amourphous core materials can be used at 20kHz and SiFe not or only with very high losses (heat).
We are just lucky that for audiofrequencies we normally don't need much power but if we do we should have a problem with the traditional iron cores.
http://www.sekels.com/vertragshaend...chnittbandkerne-aus-vitroperm-nanokristallin/
We are just lucky that for audiofrequencies we normally don't need much power but if we do we should have a problem with the traditional iron cores.
http://www.sekels.com/vertragshaend...chnittbandkerne-aus-vitroperm-nanokristallin/
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Just a note, Beware of buying transformers from overseas as the shipping may be a lot more than what it is worth.
I know of one DIY'er that has ordered some and to my knowledge, He is still waiting to receive them and it has been a few months already.
Since they have not been tested you are better off just getting the Antek's as they have been tested and work well.
They are good for up to about 4kv to 4.5kv or so before I had one fail under very extreme conditions.
Using two of them will get you into the 9Kv range with a good amplifier and this is a lot of voltage for any panel.
If you are seeking more voltage output swing then use 4 of them.
I don't expect the oversea's one to perform any better, Although I have not had one to test either.
Since they are designed for 50/60Hz the core saturation characteristics will be the same.
Stay away from the shielded types as well, if you can.
If not it is very simple to unwind the LVwinding and remove the shield and put the LV winding back on as it is only about 20 to 30 turns or so.
I don't see any reason that these would not work well for what they cost at $11,
Antek - AN-0206
I will try to get some of these to test sometime soon.
Or if you chose to have a larger core this one is a good alternative for $18,
Antek - AN-1212
Rewinding the LV for 6v is a peice of cake, or, you can just add a new winding as it is on top with some wire, as I have done in my earlier transformer testing and experiments.
This will also allow you to be able to fine tune to higher transformation Ratio as well, providing that you also use a proper higher crossover frequency than 300Hz to avoid core saturation.
You can do this with any toroid core power transformer.
One of the things about using the higher power core is that they use a thicker gauge of wire for the winding's and this also makes them less prone to fusing a winding turn should a Flashover in the panel occur.
FWIW
jer
Hi,
I have just inspected a quad ESL 63 core. Lamination thickness seems to be standard 0.3mm. Furthermore time-tested arrays of toroids show reasonably low distortion and no heating up with audio frequencies. Anyway difference between peak and average output of music is high and most energy is concentrated below about 300 Hz. What I wanted to say is that even typical 0.3mm SiFE material can be good enough for ESL step-ups. For a tube output trannie the story may be different due to higher source impedance.
Regards,
Lukas.
I have just inspected a quad ESL 63 core. Lamination thickness seems to be standard 0.3mm. Furthermore time-tested arrays of toroids show reasonably low distortion and no heating up with audio frequencies. Anyway difference between peak and average output of music is high and most energy is concentrated below about 300 Hz. What I wanted to say is that even typical 0.3mm SiFE material can be good enough for ESL step-ups. For a tube output trannie the story may be different due to higher source impedance.
Regards,
Lukas.
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