Audio in from lower left through connected grids of 12AX7 dual triode. Signal out through two connected tube plates. Above transformer is automotive ignition coil with B+ input of 100 to 300 DC volts (apparently coil secondary ). Input from tube plate to coil + (battery) and one side of 8 ohm speaker. Second speaker wire connected to coil - (distributor) connection on coil. High voltages require caution and proper insulation on these projects.
