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Old 25th December 2013, 07:54 AM   #21
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I know, real music is different then test signals.

But don't try 300W long time, these transformers are not made for these conditions. The core will heat up and the wires too. (and the high voltage + arcing is also dangerous)

For a good esl design you not need big amplifiers, just an avarage 50W is more then enough.

An an Quad 303 plays very loud on a Quad esl.

Quote:
Originally Posted by Bazukaz View Post
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.
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Old 25th December 2013, 10:59 AM   #22
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Something as this can happen:

Click the image to open in full size.



Quote:
Originally Posted by golfnut View Post
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
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Old 25th December 2013, 11:10 AM   #23
Calvin is offline Calvin  Germany
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Hi,

who talked about 300W??
But You´re right in that a efficient ESL design doesn´t need powerful amps to play very loud -though there seem to be differences about the term ´loud´
My panels -and ML´s probabely too- just warm up where the Quads already end.
The smaller panel with 1.1nF of capacitance and 0.3m² area just needs a well done 20W amp and for the larger panel with its 2.2nF capacitance and 0.6m² membrane area, the merely 50W delivering Kronzilla Tubes are perfectly sufficient to drive the panels close to their limits.
At shows guests always wondered about how just so few Watts could drive such a big ESL-system to ear shattering levels.

jauu
Calvin
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Old 25th December 2013, 06:19 PM   #24
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In ancient times, we all used tube output transformers. I still have a bunch - like a pair from the famous ultra-linear Dynaco "Stereo 70" amp and a pair of Thordarson 6V6 transformers are driving my ESL tweets.

Are these transformers suitable for ESLs like we used to think? Or do they have various shortcomings?*

Ben
*Granted, not feasible to buy a classic pair today due to stratospheric prices.
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Last edited by bentoronto; 25th December 2013 at 06:23 PM.
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Old 25th December 2013, 07:26 PM   #25
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In my opinion serious shortcomings. Step-up is (to)low and not made to drive capacitive loads, probebly the frequency respons is not so good.


Quote:
Originally Posted by bentoronto View Post
In ancient times, we all used tube output transformers. I still have a bunch - like a pair from the famous ultra-linear Dynaco "Stereo 70" amp and a pair of Thordarson 6V6 transformers are driving my ESL tweets.

Are these transformers suitable for ESLs like we used to think? Or do they have various shortcomings?*

Ben
*Granted, not feasible to buy a classic pair today due to stratospheric prices.
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Old 25th December 2013, 07:53 PM   #26
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Quote:
Originally Posted by esltransformer View Post
In my opinion serious shortcomings. Step-up is (to)low and not made to drive capacitive loads, probebly the frequency respons is not so good.
I certainly make no claim to understanding these things but...

Ratio for my Thordarsons is (1) 10-kohm on one side to (2) the tiny winding between say the 4- and 8-ohm taps on the other side... what is that ratio?

As far as frequency response, they sure cover the range when used as output transformers and have a substantial amount of iron in 'em.

And they sure were used a lot in the old days and looked vastly beefier than what you'd ever find in store-bought ESL speakers*.

Ben
*Except for Dayton-Wights with 39-lb transformers
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Last edited by bentoronto; 25th December 2013 at 07:55 PM.
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Old 26th December 2013, 12:24 AM   #27
BuyDIY is offline BuyDIY  United States
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Well, the AN-1212 is out of stock.
Going off my original post...... Should I wire in 2 of the AN-0206, or 4 per speaker.
Is 50va going to be enough, or 100va be optimal?
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Old 26th December 2013, 08:58 AM   #28
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In terms of overload/saturation it makes no difference if you have a 10, 100 or 1000W transformer.


Quote:
Originally Posted by BuyDIY View Post
Well, the AN-1212 is out of stock.
Going off my original post...... Should I wire in 2 of the AN-0206, or 4 per speaker.
Is 50va going to be enough, or 100va be optimal?
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Old 26th December 2013, 10:06 AM   #29
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I answered that Question back in post 13.

jer
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Old 26th December 2013, 10:37 AM   #30
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Are replies in two preceding posts in conflict?

Ping, ping, ping, anybody have information about using tube output transformers as per my post #26?

B.
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