Run a ground wire from the dynavector to the tonearm headshell. Does it go away?
Run a ground wire from the headshell to your main preamp. Does it go away?
If it does go away that will tell you at what point the problem is.
Make sure your rca plugs are clean and make good contacts... Most likely you have a break in your ground wire.
Other possible cause could be the pivot point needle bearing is dirty and breaking the ground, or the contacts to your cart are damaged or dirty.
Run a ground wire from the headshell to your main preamp. Does it go away?
If it does go away that will tell you at what point the problem is.
Make sure your rca plugs are clean and make good contacts... Most likely you have a break in your ground wire.
Other possible cause could be the pivot point needle bearing is dirty and breaking the ground, or the contacts to your cart are damaged or dirty.