Fixing unwanted granulation/aliasing at high frequencies

Can anyone give me advice about how to avoid granulation/aliasing with higher frequency notes? I usually start my channel at -12db, but when I play certain notes for certain patches, I get this granulation, that almost sounds like little pebbles bouncing around in the patch. I’ve read sometimes that has to do with the quality of the samples in a VST/synth. Advice?

Can you share an example so we can hear the problem? I don’t really understand what you’re describing…

Can you share an example so we can hear the problem? I don’t really understand what you’re describing…