• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Help wiring these German transformers

It´s not a myth...Look at what beyerdynamic says:

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Also STUDER says this in the same manner in their servicemanuals for their consoles.

Here is the same:

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Here you can find the entire documentation: https://www.audiomodellierer.de/VEB_Funkwerk_Kolleda.html

With voltage-matched input transformers, the current does not play a role because the power transmitted is very low and the transformer is mainly used for almost low-noise voltage gain. In this case, the change in voltage over the unit of time is crucial. This is also how induction is defined in this special context. DVMs use between 1.3 volts and 4 volts DC to determine resistance. Unfortunately, these are not myths. :) Mr. Domsch describes this very well in his book. Best regards!
Yes! A DVM magnetizes the core of input transformer. DC must be avoided.
Also high input voltages at these input transformers must be avoided. Max. input voltage iof these input transformer is 1,55 Volts ->+6dB.
Best regards!
This is from vital importance!
(Take care with ohm measurements expecially with low R ranges the current is higher and magnetization of core is much higher.)
Use only L meter.
First measure the Inductance of coils. with open ends one which are not measuring when measure the pair.
Inductance ratio is the same as impedance ratio and can be calculated. Also after deteminig prim and sec. You cam measure Lprim with shorted secondary to get Leakage inductance. Then calculate Mutual inductance and Coupling factor.
Capacitances also can be measured. That will not harm the transformer.
Still, not convincing why a transformer core should remain permanently magnetized, even after a high amount of DC applied. There is a reason they are called soft magnetics. Such phenomena would occur partially only near the hysteresis circumference. Which, especially for high-nickel cores should be much narrower than silicon steels. I cannot buy this claim, especially as detrimental factor to the transformer performance.