Sorry thats not true. You cannot permanently magnetise a soft magnetic material like mu metal. Its safe to measure the DC resistance of a core with a DMM. I do it all the time.
There will be a little bit of residual magnetism called remanence. I can pick up small laminations with a steel screwdriver due to this.
If you dont believe me about this Sowter says the same on his website
There will be a little bit of residual magnetism called remanence. I can pick up small laminations with a steel screwdriver due to this.
If you dont believe me about this Sowter says the same on his website
And anyway, it is not such a big deal to demagnetise whatever has become magnetised. Unless of course you believe VDH who says that once you start demagging, there is no stopping it. Worse than cigarettes 🙂
There is more than one thing in play when you load the secondary of a step-up transformer. If you are dealing with reflected primary impedances many times greater than the cartridge source impedance you will primarily impact the transformer ringing. If you are lowering the value of a loading resistor to the point you start to approach the generator impedance at the primary, you will lower the voltage on at the secondary. You already did an experiment that proves that with your 100 Ohm secondary load. The effect could be useful though if you happen to be overloading your preamp on transients. In that case a reasonably lower secondary impedance could be just the trick.
Conversely, if you lower the reflected primary impedance by turns ratio in the transformer, the voltage across the secondary goes up as you approach the generator impedance of the cart and then goes down again as you get very much lower. It is likely you would overload a typical MM preamp if you tried to exploit this effect with the Denon cart
Conversely, if you lower the reflected primary impedance by turns ratio in the transformer, the voltage across the secondary goes up as you approach the generator impedance of the cart and then goes down again as you get very much lower. It is likely you would overload a typical MM preamp if you tried to exploit this effect with the Denon cart