Coldsnow

How to check audio transformers secondary ohm rating?
« on: August 25, 2009, 05:59:16 PM »
How to check audio transformers secondary ohm rating?
« Last Edit: August 25, 2009, 09:06:22 PM by Coldsnow »


rodabod

Re: How to check audio transformers secondary impedance?
« Reply #1 on: August 25, 2009, 06:22:40 PM »
There aren't really enough details in your question. I'd suggest reading one of the many descriptions of how audio transformers work here, or search for the Shure transformers document/webpage, or the Jensen Whitlock article for more detail.

As a short answer to your question, transformers reflect/convert impedances. They don't have an inherent impedance as such.
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Coldsnow

Re: How to check audio transformers secondary ohm rating?
« Reply #2 on: August 25, 2009, 09:07:45 PM »
Sorry wrong question.  I meant to ask about how to tell what the ohm rating would be on the secondary. I have some 1:1 transformers and want to know if they are 10K or 600ohm. 

PRR

Re: How to check audio transformers secondary ohm rating?
« Reply #3 on: August 25, 2009, 09:51:08 PM »
Figure the nominal optimum audio impedance is roughly 5 to 20 times the DC resistance.

That won't sort your 5K from your 10K, but transformers are not hyper fussy. It will sort-out the "nearer 600" (~~50 ohm DCR) from the "nearer 10K" (~~1K DCR) just fine.

CJ

Re: How to check audio transformers secondary ohm rating? New
« Reply #4 on: August 25, 2009, 10:42:03 PM »
hook a 1 uf unpolarized cap in series and apply a signal from an oscillator.

if it is a 600 ohm winding, it will resonate at about 70 hertz,

if 10 K winding , 20 hertz.

look for a bump in your sig gen, or measure the ac volts as you sweep the circuit.
when the ac volts are equally divided between the cap and the transformer, you have resonance, so at that freq, the reactance of the cap and inductor will be the same.

don't use a 10 k resistor, the math is all screwed up due to the j operator.

and excuse me, while i  operate on this j.
 ???
« Last Edit: August 25, 2009, 10:45:01 PM by CJ »
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