Strange that there is no schematic to be found of the Siemens V77b preamp.
It is similar to the V72b amp but not equal.
It has a loop to pins 2a/2b and no capacitor at the input transformer.
This loop can be used to set the gain (externally) of the amp (similar to the Disa preamp).
Attached a schematic i have drawn (as it is symetrical it is not complete, you can fill the empty spots yourself).
If someone has an original it would be nice to add it here.
It is similar to the V72b amp but not equal.
It has a loop to pins 2a/2b and no capacitor at the input transformer.
This loop can be used to set the gain (externally) of the amp (similar to the Disa preamp).
Attached a schematic i have drawn (as it is symetrical it is not complete, you can fill the empty spots yourself).
If someone has an original it would be nice to add it here.
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