https://audioxpress.com/article/you-can-diy-the-dh-220c-mosfet-power-amplifier-part-1-the-circuit
https://audioxpress.com/article/you-can-diy-the-dh-220c-mosfet-power-amplifier-part-2-construction-and-testing-instructions
DH-220C_MOSFET_Power_Amplifier.pdf