tone arm with 10gr mass with 15 gram weight cartridge?

mijostyn
from my experience adding weight to the arm always harm somehow the sound 

You want to look at dynamic compliance @ 10 hz, that is the measurement that matters. Some cartridges only rate the cartridge at the 100 hz value. Generally you multiply the compliance numbers @ 100 hz by about 1.5x  to find the 10 hz compliance numbers. When looking at the resonance calculators, be certain to add in another 1 to 2 grams for the weight of the fasteners. As someone else mentioned, as long as you are able to balance the arm, free float, with the existing counter weight, then you should be fine. Otherwise, you will need a heavier counter weight. Below 11 grams is considered a low mass arm. 

thanks

Shucks. Ah jest tapes a penny to the top of the headshell and calls it good. (Oh wait, it's no longer April 1st, is it?)

This is my last attempt to advise, Just do it.