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 Post subject: FOUND- 1100 Ohm Primary Impedance Audio Output Transformer
PostPosted: Jan Tue 23, 2018 2:54 am 
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Joined: Oct Tue 03, 2017 7:06 pm
Posts: 33
Location: Alexandria, VA
I need an audio output transformer with a 1.1K ohm impedance to 3.2 Ohm secondary. It must be capable of handling 12W.

I am looking to spend not more than $20. Location, Alexandria, Virginia.

The primary should read about 70 ohms on a VTVM.


This is for a 1940's Westinghouse with parallel 6Y6.

Thank you.


Last edited by Lebowski on Jan Wed 24, 2018 5:18 pm, edited 1 time in total.

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 Post subject: Re: WTB 1100 Ohm Primary Impedance Audio Output Transformer
PostPosted: Jan Tue 23, 2018 3:01 am 
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Transformers do not have impedances.
They have impedance ratios.

The impedance (resistance) connected to the secondary sets the primary impedance.

In this case, the ratio would be 1100:3.2 = roughly 330:1.

- Leigh

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 Post subject: Re: WTB 1100 Ohm Primary Impedance Audio Output Transformer
PostPosted: Jan Tue 23, 2018 2:17 pm 
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Joined: Oct Tue 03, 2017 7:06 pm
Posts: 33
Location: Alexandria, VA
Thank you, Leigh

So I am looking for a transformer with a 18:1 turns ratio?


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 Post subject: Re: WTB 1100 Ohm Primary Impedance Audio Output Transformer
PostPosted: Jan Tue 23, 2018 5:31 pm 
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Lebowski wrote:
So I am looking for a transformer with a 18:1 turns ratio?
Yep.

For anyone who didn't understand the question...
The impedance ratio is the square of the turns ratio
or alternatively
The turns ratio is the square root of the impedance ratio.

- Leigh

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 Post subject: Re: WTB 1100 Ohm Primary Impedance Audio Output Transformer
PostPosted: Jan Tue 23, 2018 10:19 pm 
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Joined: Mar Tue 13, 2012 6:56 am
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Location: San Diego
This Edcor should work, although there is a long lead time since they are made to order: http://www.edcorusa.com/xse15-25k

Having two 6Y6 in parallel will result in a total plate current of about 130 mA, which is a lot for a single-ended stage. That limits your transformer options. The Edcor above is rated for 130 mA, which doesn't give you any headroom. If you mention to Edcor your intended application, they may be able to modify the design to allow for a bit more current on the primary winding.

Also, note that the DC resistance of the primary need not be the same in a replacement transformer.

Matt


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 Post subject: Re: WTB 1100 Ohm Primary Impedance Audio Output Transformer
PostPosted: Jan Wed 24, 2018 1:43 am 
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Joined: May Fri 04, 2012 10:39 pm
Posts: 1297
Location: Hidden Valley, AZ
Leigh wrote:
Transformers do not have impedances.
They have impedance ratios.

The impedance (resistance) connected to the secondary sets the primary impedance.

In this case, the ratio would be 1100:3.2 = roughly 330:1.

- Leigh


Technically true, but they are all sold by plate load impedance, not turns ratios.

DDG

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 Post subject: FOUND WTB 1100 Ohm Primary Impedance Audio Output Transforme
PostPosted: Jan Wed 24, 2018 5:17 pm 
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Joined: Oct Tue 03, 2017 7:06 pm
Posts: 33
Location: Alexandria, VA
No longer needed, thank you.


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