oh yeah, thanks for the catch! Tomorrow I will post a correct version! I'm very scared and tired: there are few hour between me and my exam (analisi matematica 2= math. analysis 2, E.E.)
I will use 4558, or tl082 or -72; in my next order i will pick up some ne5532, because in many application they are more useful than 4558!
For the NPN, can a 2n2222 work well?It should not be very noiseless. I have a great amount of trannies to try in it, including old Ge and old Si (VHF, UHF). I saved them from my grandma's spring cleaning...