Gradient question

Hy guys.
I was wondering if you can help me out with something. Whenever I use a gradient fill, and add some levels or smth like that i get this phenomena:

How can I avoid those waves? Thank you

Add a subtle grain over gradient.

Or a bit of noise, 1 or 2%, and go for 16 or 32bpc.

Awesome. Thanks a lot guys. Very helpful