Before I started studying electrical engineering I gained 90% of my knowledge about electronics by making (sometimes modified) clones of existing guitar effects. Since they usually required some troubleshooting to get them to work this thaught me a lot about analog signal modification and general audio electronics.
When graduating Highschool I decided that a tube overdrive for my bass guitar would be my goal. To realise this, I modified the schematic of the Vanilla overdrive to be better suited for bass guitar.
As I started studying electrical engieneering I continued making guitar effects. During my study my designs evolved from DIY kits to totally custom designs, included specially designed pcb.