[sdiy] what opamp for "warmth"? (I know, I know...)

[Jay Schwichtenberg]

For cheap solutions I think OTAs, tubes and guitar circuits are the answer.

But if you can define what the function is that you want to give you 
your warmth there might be a solution but more complex than a single amp.

Diodes doing a piecewise linear circuit to approximate what you want 
might work. Also check out Chapter 1 Function Fitting in Analog Devices 
Nonlinear Circuits Handbook for other ideas.

Jay S.

https://www.analog.com/en/education/education-library/nonlinear-circuits-handbook.html