Studer 961 mic input

Hey guys
Does anyone here know the low down on this mic input topology?

I always thought it was a pretty straight up transformer + ne5534 type pre, but then I browsed the service manual, and there it was. A strange topology with two transformers wrapped in a feedback loop..

This to me is one of the sweetest sounding pres, I've heard. Nice and natural, but with a certain colour. Those Swiss geniuses must have figured something out.

There would be nice to have the specs of those tx to see how are they working and get a sim going, this parallel and center tap I don't know where they are but they define the gain/fb.

Seems to be current transformers or something like this.

JS

The service manual doesn't seem to have more info on those trannies.. The BOM simply adds, that they are manufactured by Studer.
Maybe there is a data sheet somewhere on the interweb?

You cut off the US Patent number.

Look that up. It's supposed to be a public description of the invention, giving enough information to make use of the idea. Yes, patent papers are often obfuscated so you can't really know WHAT it says, but it's a clue-point.

Right, sorry.
US patent number 4,567,443
The gist, I think, is using feedback to keep flux low, allowing a smaller and cheaper transformer. I would probably choose to believe that the emphasis was on the smaller, as this was not a cheap product 

Anyone know of other implementations of this basic idea?

We've (off course) been there before: http://www.groupdiy.com/index.php?topic=29984


Jakob E.

Thanks Jakob! I tried to search, but it didn't turn anything...
Looks like you need to wind your own iron to make this scheme work for DIY. Oh well..