Hello Radd47,
you can not just remove the filter, if you do so you end up with a rise 6 to 8dB an octave over 12kHz, lots of noise and a high chance picking up RF in settings over 30 dB...
In order to properly change the frequency response, the pot inductor made from ferrite (80/120/M/fr) need to be reduced to allow a flat response to 20 kHz. Some people replace the inductor with a resistor, in my opinion it is a half backed solution because you still have a 3dB rise... The V76S and some M versions have a NI alloy inductor.
Each of the two stages has a 60dB gain possibility, but B+ limits the max. gain (what means useable studio condition) to approx. 100dB. Open loop won't work stable, you end up with high frequency oscillation at about 35 to 40kHz, you wont hear it but it loads down your unit, if you open the 3rd/4th stage loop you end up with sub sonic oscillation at 2 or 3 Hz.
With 76 (some have 60 or 66) dB of gain and a good mic, you can listen to nearly everything....
The input core is the same size than V72/78/77/75, a specialty NI/FE/CO alloy only made in germany. The size is given by the requirement of distributed capacitance....
The historic Mu-Metal shields are RF heated in a hydrogen atmosphere to get the highest point of permeability, the new ones are RF heated in vacuum, due to the violent nature of backfiring hydrogen. A minor ding should not cause a problem.
In the new V76S and M the same EI multi taped inductor is used than in the historic V76S units.
Best regards,
Oliver