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Please rec. step-up transformers for ESL
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Old 19th September 2005, 02:05 PM   #11
furly is offline furly  Canada
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Calvin,

I may be repeating I_forgot here, but just trying to get this straight. Are you saying that you can substitute the audio transformer using for example two 230/12v toroidal power trannies in paralell to get a step-up of about 1:40?

If this is the case this seems like a much cheaper substitute especially for a first time builder. Is there anything else I should know about this?

furly
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Old 19th September 2005, 02:35 PM   #12
Calvin is offline Calvin  Germany
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correct
but Iīd prefer to use two 230/9V (i.e 1:50 just for bigger cells) or 230/6V (1:75) for small to medium sized cells.

my panel is kinda ML-Style with 125x25cm and a d/s of 1.1mm. So quite high capacitance and efficiency. Wire-panels like the Audiostatics normally need higher stepup-ratios as do panels with larger d/s.

jauu
Calvin
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Old 19th September 2005, 05:29 PM   #13
furly is offline furly  Canada
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I See.

What do you think of these?

http://cgi.ebay.ca/5x-New-Toroidal-T...QQcmdZViewItem
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Old 20th September 2005, 11:43 AM   #14
Calvin is offline Calvin  Germany
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Hi,

can be ok with panels like ML Prodigy (45x125cm 1mm, high efficiency, hybrid-style from 250Hz upwards). Should give around 85dB. Other panel-concepts will probabely be too low in SPL and give probs finding an appropriate woofer.

jauu
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Old 20th September 2005, 11:57 AM   #15
furly is offline furly  Canada
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Calvin,

Do you think I could also use one of these in my DC power supply, or do you think the step up would be too large. Keep in mind i will have a 120VAC input. I guess i could always drop the voltage down a little if it is.

Or maybe i could use 3 in parallel for a ratio of about 1:60 for my audio signal to increase the voltage going into the stators . I'm thinking of these scenarios bc these transformers are cheap which is what i'm looking for right now!!

Any thoughts?

Thanks for all your help!

furly
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Old 30th September 2005, 01:57 PM   #16
dstockwell is offline dstockwell  United States
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Do you all have on-line sources for the trannies, either the 70 volt or the toroidal's.
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Old 2nd October 2005, 02:01 AM   #17
BillH is offline BillH  United States
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Scroll down this page for five 70 volt transformers, and here's a page explaining 70 volt audio systems.

Allelectronics has a toroid transformer that looks like the right voltages, but low power handling. 115/220 volt primary, 8.5 volt at 1.1 amp secondary.

How does this look for wiring two transformers together?
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Old 2nd October 2005, 02:18 AM   #18
homemade is offline homemade  United States
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How does one determine the step-up(turns)ratio of 70v type transformers?
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Old 2nd October 2005, 04:01 AM   #19
I_Forgot is offline I_Forgot  United States
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Quote:
Originally posted by BillH
Allelectronics has a toroid transformer that looks like the right voltages, but low power handling. 115/220 volt primary, 8.5 volt at 1.1 amp secondary.

How does this look for wiring two transformers together?
That would be the way to do it. You could also wire the primaries in series for lower voltage out -unlikely you'd want that. However, if your amp should prove unstable with the primaries wired in parallel, you might try the series connection and see if the amp behaves itself.

A pair of those ought to have sufficient core area for driving an ESL.

I am still interested in hearing about how using power transformers works for driving speakers. Let us know your results...

I_F
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Old 2nd October 2005, 11:20 AM   #20
Calvin is offline Calvin  Germany
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Default Trannies

Hi Folks,

the question arose wether standard trannies are capable of good performance.

First a little History: when I build my first wire-stator-panels -which were a very low capacitance design- I bought trannies from a company that built ESLs their own. I connected 4 of them in series/parallel-connection for a ratio of 1:100. The results were not very pleasing with regard to measurements. Restricted bandwidth and phase-response. With my new metal-sheet-panels results were even worse. You can see it in the diagrams marked "..TR 1-100 EI-Type".
For me the trannies looked like 10VA-Types, so I bought me a bunch of cheap standard 230V/6V EI-Type power trannies and connected 6 of them in series/parallel connection. What should I say? The results were identical sonically as well as measured!! And while 3 out of 8 of the audio-trannies have been killed by internal flashovers the standard power trannies still work fine
Later I got the fantastic Amplimo Toroids with an ratio of 1:75. As the diagram prooves the measurements show excellent results. So I tried simple halogene-light-trannies (12V/230V) in series connection to give a ratio of 1:40. As can be seen in the diagrams, the results are very close to the Amplimo (differences in amplitude-response result from different measurement distances. Watch out for different scalings in the impedance plots!)
Apart from different SPLs and impedance levels the curves look pretty much the same with regard to upper frequency and phase responses and the apperance of the curves.
The upper bandwidth limit in frequency response results from a resonance of the panelīs capacity and the trannies stray-inductance. The point of minimum in the impedance curve around 10kHz to >20kHz defines the upper frequency limit (clearly obvious in the "EI-Type-diagrams). Too the phase response turns from theoretically 90° back towards 0°. Above that frequency the amplitude falls with 12dB/oct. So the impedance and phase curves are very good indicators for the trannies quality! With the Amplimo toroid as well as the simple halogene-lighting-toroids the phase is closer to 90° and more linear. The impedance minimum lies above 20kHz. The amplitude response is linear to 20kHz.
By using the standard toroids with a higher ratio the upper bandwidth limit will come down, but You may counter it by paralleling more trannies. Each doubling of trannie-count will result in a halfing of stray-inductance --> hence doubling the upper resonance-frequency/bandwidth limit.

Sonically I havenīt heard any differences between trannies with comparable frequency and phase-responses. Which isnīt such a surprise to me, because most trannies, wether they are marked for audio or other uses, feature the same core materials, the same wires and same insulation. The main difference are intersected windings. But with a toroid the coupling of primary and secondary windings is obviously very good and therefore stray-inductance is small. So there is hardly a need for more complicated and complex windings as in EI- or UI-Types. As long as the insulation is sufficient, standard toroids should work even better than most of the audio-trannies -- probably even with higher constancy of parameters and its much cheaper too The insulation of power trannies standardly is specified to 4kV, sometimes even 5kV@50Hz or @400Hz (in Europe) which is more than sufficient for high efficiency-designs like the ML-Panels. Interestingly a ML-Prodigy panel measured originally 1:75 and with an Amplimo 1:75 gave much more linear results for the Amplimos. The positive sideeffect was, that the complex and efficiency-killing corrective networks could be omitted...leading to a drastically higher efficiency of around 96db/2.83V/2m and sonically to a more refined, clearer and more dynamic sound. With even bigger panels PA-uses come into mind, where a lightweight Panel with compact dimensions and the specific dipolar-cylindrical sound pattern could be very interesting

I for my part strongly opt for trying standard power toroids in first case, before trying expensive īaudioī-trannies.

jauu
Calvin
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File Type: pdf panel nearfield tr amplimo 1_75.pdf (62.8 KB, 98 views)
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