What can I do with these input transformers

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thomasdf

Well-known member
GDIY Supporter
Joined
Aug 10, 2011
Messages
966
Location
Paris, France
Hi all

I was given a pair of Melodium input transformers. These are french xformers, pretty high standard. The only thing is that the primary is 22,7 ohms and secondary is 96 ohms. They were used as input transformer in a modest PA console.
What can I do with these? I know some guy built passive DIs with similar transformers...
I am more interested in a mic preamp... even a very simple one...

They are the same as this one:

KNfNmaXl.jpg


Any advice is welcome!

Thanks a lot

Thomas
 
When you say they measure 22.7 ohms and 96 ohms, do you mean those ore the dc resistances of the windings?

Do you have a part number for the transformer?


Cheers

Ian
 
> They are the same as this one:

"Vous n’êtes pas autorisé à télécharger ce fichier joint."

Which I think means "You can't see this!" (Probably need a log-in to autorisé me.)

As Ian implies, DC resistance is NOT the audio impedance.

As a rough guess, nominal audio impedance is 10X higher. So 22:96 DC is probably 200:1K audio. Nice low ratio for general transistor preamps. Not enough step-up for lowest hiss in most tube preamps.
 
PRR, good guess! It meant "you are not allowed to download that file", I took it from another forum.
Anyway, I re uploaded it.

It's good to know that DC resistance is not the same as impedance (I kinda knew it I guess...?). How can one measure the exact impedance then?

I can shoot at any transistor preamp that needs 1K at its input then?
 
I'd love to build a germanium preamp with these, I've been looking around and I may give a shot at the Jensamp, do you think they would be appropriate? I am also hesitating between transformer balanced output or unbalanced output...
 
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