Dear Toufu: I can't say if the Zu is a good match for the tonearm you own ( ask directly to the manufactirer about ) but if it is then the problem is in other " place ".
The Zu specs " talk " that the recommended VTF is 2.5grs but this manufacturer does not point out a VTF cartridge limit ranges ( up-down ) like almost any other cartridge builder so maybe the Zu can run " safe " up to 3.0grs we don't know about and you have to ask, here too, directly to the manufacturer.
The " right " VTF is not only for the cartridge track fine with out tracking distortion and to protect the LPs from fast wearing but along the suspension design to center the coils to achieve the quality performance design targets.
If your cartridge is out of that " right " VTF then all those factors name it could suffer a " degradation ".
+++++ " but for some classical recordings, the strings have some silbius or distortion.... " +++++
Toufu your cartridge ( like any other one ) is not a perfect one, it is far from there, the ZU performs according its price range or something a little better: nothing more nothing less.
In the other side all the recordings are far from be perfect too so you must accept " distortions " all over the analog music sound reproduction.
Maybe you are " waiting " that your analog rig performs near perfection. Well you can't wait or look for in your today audio system, you have to accept its limits.
Anyway, IMHO it will be worth to contact directly to the Zu manufacturer and explain to them what you are experienced and see which advices and support they can give you, maybe your cartridge is out of specs somewhere.
Regards and enjoy the music.
Raul.
The Zu specs " talk " that the recommended VTF is 2.5grs but this manufacturer does not point out a VTF cartridge limit ranges ( up-down ) like almost any other cartridge builder so maybe the Zu can run " safe " up to 3.0grs we don't know about and you have to ask, here too, directly to the manufacturer.
The " right " VTF is not only for the cartridge track fine with out tracking distortion and to protect the LPs from fast wearing but along the suspension design to center the coils to achieve the quality performance design targets.
If your cartridge is out of that " right " VTF then all those factors name it could suffer a " degradation ".
+++++ " but for some classical recordings, the strings have some silbius or distortion.... " +++++
Toufu your cartridge ( like any other one ) is not a perfect one, it is far from there, the ZU performs according its price range or something a little better: nothing more nothing less.
In the other side all the recordings are far from be perfect too so you must accept " distortions " all over the analog music sound reproduction.
Maybe you are " waiting " that your analog rig performs near perfection. Well you can't wait or look for in your today audio system, you have to accept its limits.
Anyway, IMHO it will be worth to contact directly to the Zu manufacturer and explain to them what you are experienced and see which advices and support they can give you, maybe your cartridge is out of specs somewhere.
Regards and enjoy the music.
Raul.