Telefunken Transformers

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Again, thanks C.J.  :)

Oliver maintained that  all the V72S modules in the REDD desks had a special 'studio' version of the IPT.  Do you know what the difference was in the spec? 

Edit:  The transformer I sent to you for dissecting all those years ago came from an EMI modified "S" version and I found an old online discussion I had with Oliver regarding that particular transformer vs the ones from Siemens & Halske "S" modules.  Since poor Oliver is no longer here, I'm just trying to ascertain as best I can what the difference might have been.

https://repforums.prosoundweb.com/index.php?topic=24916.0 
 
hey Winston!

feedback was reduced on the S to give it more gain,  this was done with a divider,

went from 34 to 40 dB or something like that,

cj

edit: wait, you already know that part, input transformer, hmmm,let me take a look...
 

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Yep, take a look at my edit above. 
I think the difference was just in the order in which the coils were placed and connected but... ?    ;D

Some more words from Oliver:

"The so called EMI version the V72S, input is hooked up the same than the IRT but the coils are wound different and mechanical in phase, instead the out of phase of the IRT version."

and:

"The actual x-former is the same, it is the way the coils are hooked up, V72>v72S and V76>V76S is identical how this was done.
In order to change the set up, you have to take the x-former apart, place the coils in the right order and hook them up to S specs...

Do not try this at home..."

 
i believe they flip one of the primary discs so that the connection goes S-F-S-F

instead of S-F F-S like the stock model,

the discs are wound and varnished, then they slide them over the core, so you can have a reverse wound primary disc simply by putting it on backwards and swaing the leads.

why they did this i do not know, having them assembled with on flipped would cancel some input noise and any phantom switching would push the coils towards each other and cancel mechanical motion,

the way EMI switched it, both coils would move in the same direction but this is damped out with the rubber bumper at the end of the core.

maybe hi end was improved by flipping the coils as capacitance to ground would change,

or maybe negative feedback is changed, as when those discs move to one side, you are losing a bit of flux as the energy is turned into mechanical motion.  this results in a little loss of signal at the low end as the discs are too heavy to respond to hi frequency motion.
 
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