In my Halcro DM10 preamp, the MM/MI phono stage has adjustable Capacitance and Resistance.
I find that changing the resistance has a far greater subjective effect on the sound of the cartridge that the Capacitance (all things being equal).
The distortion in the high frequencies you are experiencing may be a case of too high a VTA as MoFi suggests or could be a tracking weight issue?
Then again, the 5mV output of the Ortofon may be 'overloading' the gain of your phonostage?
I find that changing the resistance has a far greater subjective effect on the sound of the cartridge that the Capacitance (all things being equal).
The distortion in the high frequencies you are experiencing may be a case of too high a VTA as MoFi suggests or could be a tracking weight issue?
Then again, the 5mV output of the Ortofon may be 'overloading' the gain of your phonostage?