Anyone know of a US source for ESL toroids? - Page 8 - diyAudio
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Old 28th November 2011, 11:41 AM   #71
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100 MHZ ?
You can only use multiples of 2 and the drive configuration.

Say that your pirmary winding is rated at 5v (in this case) at 60Hz than that is all you can put into that winding at 60Hz before the transformer will start to saturate.
Ii you Double the frequency than you can double the voltage and so on.
So at 150hz you can do 15Vrms input to the transformer and 30 vrms at 300Hz and this will get you into the 100 watt amplifier power range in to 8 ohms.

So if you plan on using a 500hz crossover then 480hz is 8 times and you can put as much as 40Vrms into the transformer without it distorting (saturation).
This will be a lot of power handling at this point as every time you double the voltage the power goes up 4 times as much for the same impedance.

The same works in reverse.

Yes you can use more cores to get a better lower frequency response.
But, your high frequency response become an issue.

Because now that you have added more transfomers this adds more residual capacitance and more power is wasted as heat in the transformer system.

Due this raised capacitance the resonate frequency of the transformer system gets lowered and may be well below 20 khz limit of the audio band.

When the amplifier is required to reproduce this particular frequency it becomes an extreme load on the amplifier and basically looks at it like short circuit and overloads the amp in a big way.

I did a very long study on this last year and it a thread that is a must read inorder to help you understand how the transformer works for an ESL.

There are some links in some recent threads,But if you can't find them I would be happy to dig them all up and repost them for you.

jer

P.S. I forgot that those transformers have two 120v windings so yes you could use 3 of them, but you will have the same issue that I have just described and I have done this but the performance is marginal for what it is worth and cost.

Last edited by geraldfryjr; 28th November 2011 at 11:44 AM.
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Old 28th November 2011, 08:26 PM   #72
Calvin is offline Calvin  Germany
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Hi,

two or multiple of two trannies is the way to go.
Saturation of the core is a result of too high currents in the windings, resulting in too high flux. Its not a direct result of the applied voltages. Increasing the inductance of the windings and increasing core size helps (usually both going hand in hand). With increasing signal frequency the allowed power rises. On the other hand toroids react quite sensitive on a DC-component in the signal.
EI and UI-cores are less sensitive to DC.
I wouldn´t recommend a simple power toroid tranny for fullrange use, but its a handy solution for hybrid panels and freqs >100Hz.

The upper bandwidth limit is defined by the trannies stray inductance (which is usually low with toroids) and the panels capacitance and stray capacitances (which may be are rather high with toroids). Still though the toroids I described in an earlier thread showed an upper bandwidth limit of >20kHz with 2x80VA, 6V/230V, 1nF-panel and app. 19kHz with 2x120VA, 6V/230V, 2nF. At the resonance frequency the ohmic part of the impedance is lowest, but the phase shift becomes 0°. Since this is at the extreme audio frequency range end where the signal content is small and low in level, this usually (and against most of all the rubbish talk the mags still publicate about ESLs) presents no problem to the amplifier. It is rather the freq range between the inpedance maximum (usually to find at a couple of hundreds of Hz) and this upper minimum. Here the low loss nature of the toroids (tight coupling) hits hard. The ohmic part of the impedance is still sufficiently high enough for almost any amp, but the phase shift may sink, close to the ideal capacitor value of -90°. This enourmous phase shift troubles all but a very few amplifiers that feature global feedback loops. If not turning into an power oscillator or an heatgun at once the poor amp definitely will sound stressed and crappy.

jauu
Calvin
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Old 12th January 2012, 02:07 AM   #73
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I recently found some 50VA single primary 230v/2x6v toroids from a company in England that will accept a US credit card and ship to the US-- don't know how good they are but, @ $18 each + $20 to ship (4) of them to my US address, the price is certainly reasonable (and I'm thinking these would be less apt to shorting than the dual-primary Anteks). Last week they had six in stock but I checked today and they were sold out/on backorder. Anyway, here's the link:

Toroidal Transformer 230v Single Primary 50va 0 6v 0 6v

In order to buy from this company, you first have to register at their website and enter a phone number using the US international calling prefix "011" and you must use spaces rather than dashes between the number groups (example: 011 xxx xxx xxxx). Also, there is no place to enter a state in the address field but if you put your state's two letter code after the city, in the same box, that will work.
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Old 17th November 2013, 01:52 PM   #74
BuyDIY is offline BuyDIY  United States
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@Charlie

Did you ever purchase the toroids from the company in England? If so, how did you like them? How long did it take to get them?

Thanks
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Old 17th November 2013, 05:33 PM   #75
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Quote:
Originally Posted by BuyDIY View Post
@Charlie

Did you ever purchase the toroids from the company in England? If so, how did you like them? How long did it take to get them?

Thanks
I've not made any purchases from that source -- just posting the information for others, since I know how hard it is to find a source for 230V/6V trannys that will accept a US credit card and ship to the US. Their website says they process the orders within 2 weeks, but that would not include the shipping time. You might try calling to ask.

Most builders spend weeks or even months on an ESL project, so I can't imagine the order-time on those transformers would be a problem.
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