Ideally, in any high-gain circuit, you want to try and avoid feedback between output and input by keeping them as far apart as possible. Similarly you should keep high-voltage AC (mains wiring, speakers, motor supplies) away from sensitive audio circuits. With stripboard this means avoiding having input and output on parallel adjacent tracks.Thanks for checking. When I was wacthing a video of how to make audio stripboard circuits, something was mentioned about that some inputs or outputs should not be placed to adjacent stripes. But I can't remember which ones were mentioned and I don't find the video any more. Which in or outputs could the video refer to?
Thanks noted!You are missing a power supply decoupling capacitor.
For this circuit, I would put a 10μF / 16V electrolytic capacitor between +9V and GND.