Here the schematic diagram of 70W power amplifier with MOSFET for your audio system.
There are possible alternative input stage transistors, the Toshiba 2SA970BL and 2SC2240BL, which appear to be good substitutes for the Hitachi 2SA1085E and 2SC2547E. The ‘BL’ suffix is the high gain group. Alternatives for the Sanyo 2SC2911 and 2SA1209 are the Toshiba 2SC3423 and 2SA1360.
This 70W power amplifier is designed for quality rather than quantity, and if much higher power is really needed there are other more suitable design approaches.
This is an awesome amplifier circuit, and this is the older version (MJR7-Mk3). There is new version released (MJR7-Mk5) for better quality and performance, just go to THIS PAGE for complete circuit explanation.