This is my first amplifier based on transistors. Couple of time I use bu508afi and bu426a hv transistors. One time I try experiment with another transistors. I make darlington double with bu426 and 508 and now I couple 2t6821 and s8050 pnp to them. The result is sound normal as radio on battery but very low. The power supply is charger from mobile phone with 5v 0.65mA. How on time I listen music I feel and smell one of transistors is overheat that was a 2t6821. He have to32 or to18 metal case but hardly is cooling. Then couple of days he isn't work.
