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Siemens / Haufe Input  Transformers - Tech Site
   

  This page will give technical advice how to use Siemens / Haufe input transformers as step up transformers for Moving Coil pick up cartridges.

 
1. Determine the input and output winding(s)    
moving coil pickup cartridge step up transformer

  Before thinking of using them as input transformers, be sure you really have a pair. Similar looking units can be pretty different!

 

  For step up input transformers (as T41, T42, T110 a.s.o) goes:
- input winding DC resistance is between

  3 and 500 Ohms
- output winding DC resistance is between

   1.5k and 8.5k.

  Even transformers coming from the same preamp can be different. T41s i.e. range between 350 and 450 Ohms on the primary and 7.5k and 8.5k on the secondary windings.

  Many transformers have a pair of twisted leads which represent the input winding.
  In many instances the output winding is a single lead and 3 to 5 leads soldered together (some of these are grounding leads or connected to the mu metal can).  The T41 i.e. usually has 4 leads soldered to ground. See its schematic on the left.

  Caution! Many windings are defective. Connecting higher output or active units to the input transformers many input windings have been killed. If you do not find a pair of working winding this may be your case. 

   
   
moving coil pickup cartridge step up transformer    
   
   
   

Matching is recommended if possible...

 
moving coil pickup cartridge step up transformer  

moving coil pickup cartridge step up transformer

 
   
   
2. Built the trannies into a case or into your amp    
moving coil pickup cartridge step up transformer     I recommend using different input transformers for different cartridges (as T41 for Denon DL-103 or T110 for the EMT Tondose), so that impedance matching (adaption with resistors) is not necessary.  
    I wire as seen left. The (twisted) primary winding to the input jack, a jumper connecting the ground connectors of the RCA jacks and then the ground cables and the secondary winding to the output jack.  
    It is very important to properly phase the windings (never trust the colors of the leads). Using a scope this is pretty easy.  
Out of phase   Properly phased  
moving coil pickup cartridge step up transformer  

 moving coil pickup cartridge step up transformer

 
               inside the transformers    
moving coil pickup cartridge step up transformer  

  Under the yellow or orange tape the mu metal shielding cans can be seperated to look inside the transformer.

 

  In many cases the PU foam has dried out and does not keep the winding in its correct position. This is not audible, but the thin cables can be cut when the transformer is shaken.

 

  

       
moving coil pickup cartridge step up transformer  

  Another way of matching is to measure the impedance curve of the transformers (left).

  Residual magnetism (dtsch. Remanenz): Using a digital ohm meter I could never measure any negative effects.
I have demagnetised units after testing and could not see any difference. So, do not worry.

  

 
 

 

 
           

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