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Audio output transformers - again

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Forum » Technique, Repair, Restoration, Home construction ** » Radios: how to get parts for old radios » Audio output transformers - again
           
Ralph Musto
Ralph Musto
 
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26.Oct.17 23:07

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Can anyone recommend a good source (in Europe) of replacement audio output transformers?

I know the audio-amp squad have made these items quite expensive these days, so eBay does not offer anything too appealing at the moment.....so what is the best place to look now?

Many thanks,

Ralph

(I read the interesting post about using line matching transformers, but note the potential problem with no gap in the core of these items)

 

 

Heinrich Stummer
Heinrich Stummer
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27.Oct.17 12:17

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Hi, take a look

die Wuestens

Hammond  many distributors in Europe

röhrentechnik

Welter

audioelektronik

 

Ralph Musto
Ralph Musto
 
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27.Oct.17 21:39

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Brilliant - thanks Heinrich.

 

Michael Watterson
 
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29.Oct.17 21:45

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The magnetism due to DC bias currents cancel If it's "push pull", so a multi-tap line transformer (if 1K and 4K then 1K is the centre tap) or a 110 - 0 - 110 transformer can be used. Ohms ratio is the square of voltage ratio and the DC resistance isn't the "Ohms" load of the output valve. Note the mains transformer power rating is at 50Hz or 60Hz, so it can handle higher audio power as on average it's more than 10x the frequency and the core size needed is much less (that's one reason SMPSU uses 25KHz to 2MHz, to use a small transformer). A toroidal transformer needs well matched bias currents, avoid them.

For Class A / Single ended a larger size mains transformer can be used to avoid saturating the core, especially on battery valves and less than 2W power out valves/tubes.

Ralph Musto
Ralph Musto
 
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30.Oct.17 11:51

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Hi Michael,

Thanks, interesting info.

Funnily enough, I was mulling this over yesterday and wondered about using a mains transformer for this task, so good to have your input.

I'll have a dig around and see if I have one that I can try.

Ralph

  
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