Helo Zapper,
Nirāmisa sukha is a “general sense of well-being” and NOT a particular vedanā (like when eating a tasty meal).
It comes gradually as the mind is cleansed of lobha, dosa, moha.
There is the following sutta where a former king/aristocrat who became a bhikkhu expressed it as “Oh, what bliss! Oh, what bliss!”
– The other bhikkhus thought he was thinking about the enjoyments that he had given up. But he explained that it was exactly the opposite.
“Bhaddiya Sutta (Ud 2.1)”
– We don’t realize the burden that we carry when we are enamored with worldly possessions.
– When you start seeing the “anicca nature” of those possessions, you gain nirāmisa sukha.
– It just happens over time.