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Old 12th December 2006, 11:55 PM   #11
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It should work just fine.

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Old 13th December 2006, 01:05 PM   #12
Calvin is offline Calvin  Germany
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Hi,

maybe just to get some things clearer for You.
The Bias voltage and the trasformation factor have nothing to do with each other in first case! You donīt design the transformer ratio after some DC-Voltage on the diaphragm, but solely for good efficiency and based on the geometrical and electrical design of the panel.
Regarding this it should be Your aim to design the panel such that the transformer ratio could be as low as possible. I prefer to stay well below 1:100 since as a result these designs sound better, have greater dynamics and play safer.

jauu
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Old 14th December 2006, 01:59 AM   #13
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Ahhh i see.

I am trying to make some small esl's now. I have run into a problem, i am useing a ac adapter tranformer backwards and a voltage multipler as a bias. The secondary windings on my tansformer read 2 ohms. I have another ac adapter and the secondary also reads 2 ohms. The primarys are 2kohm. When i try to power it up my 5 amp fuse blows, i try to add resistors in line to bring the resistance down and the resistors burn up. What is going on?
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Old 14th December 2006, 03:25 AM   #14
BillH is offline BillH  United States
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Hi, ak.

Where is your fuse wired in? If you can give us a diagram of your wiring, we should be able to help.

Here's a diagram from Mark Rehorst's web site that shows how to connect the parts if you have a center tapped step up transformer.

Click the image to open in full size.
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Old 14th December 2006, 05:40 AM   #15
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Quote:
Originally posted by ak_47_boy
Ahhh i see.

I am trying to make some small esl's now. I have run into a problem, i am useing a ac adapter tranformer backwards and a voltage multipler as a bias. The secondary windings on my tansformer read 2 ohms. I have another ac adapter and the secondary also reads 2 ohms. The primarys are 2kohm. When i try to power it up my 5 amp fuse blows, i try to add resistors in line to bring the resistance down and the resistors burn up. What is going on?

If you use your ac adapter backwards, you are connecting the secondary to the mains? That doesn't work, the current from the mains into the secondary is too high. If the fuse wouldn't blow, the adapter would! That transformer never was designed to take a magnetic flux that is an order of magnitude higher than normal. The core saturates which drops its impedance for the mains current to almost zero (or the wire impdance of 2 ohms in this case).

You can probably use a normal adapter of say 24V sec, and then a second one say 12 to 120 (or 220 if you are in europe) connected sec to sec, so at the end you end up with several 100 V, isolated, and then try your multiplier.

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Old 14th December 2006, 08:28 PM   #16
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I thought more windings would always mean more resistance and therefore less current would be used?
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Old 14th December 2006, 08:32 PM   #17
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Could i hook my doubler right to the 120 supply from the wall? I only need about 800V.
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Old 14th December 2006, 09:31 PM   #18
maudio is offline maudio  Netherlands
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Quote:
Could i hook my doubler right to the 120 supply from the wall? I only need about 800V.
In theory: Yes. But if you plan on building a next project afterwards, I suggest you try to survive this one...

So for safety reasons, use two transformers connected back-to-back:

T1: 120v>xxV
T2: xxV>120V > feed that into your doubler

You don't need any power, a set of 1 or 2 VA trannies will do. Sec voltage (xx) is unimportant either, as long as both transformers are equal. Such small trannies are cheap. Don't try saving 5$ here, don't mess with mains if you don't have to.

Also don't get tempted to feed say 12V form a 120/12 into a 6/120 to get 240V out. It won't work. As a rule of thumb, a power transformer's core will saturate about 20% over it's rated voltages. Cores are expensive, you can count on it that the manufacturers squeeze the max out of them.

Also don't forget to place a resistor of 22..100MOhms in series with the doubler output, to limit the current.
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Old 14th December 2006, 09:43 PM   #19
maudio is offline maudio  Netherlands
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Quote:
Originally posted by ak_47_boy
I thought more windings would always mean more resistance and therefore less current would be used?
What counts is the amount of flux generated in the core. All depends on # of windings and frequency divided by core area (what matters is the flux density).

When the flux density hits the ceiling (around 1.5T for iron) the windings lose their inductance, all that remains is the DC-resistance. And 2 ohms over 120V will try to draw 60 amps ...
It's a good thing to have fuses
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Old 15th December 2006, 07:16 PM   #20
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Ahh i see, boy i am glad i had a fuse in there.
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