GFA 5300 is an amplifier made by ADCOM which is able to producing an audio output of 80 watts.
The amplifier was made in the late 90’s but was still widely sold in the 2000s.
The schematic diagram of this circuit is quite different.
Almost the same as circuits that use transistors, only that there are several components that must be installed around the MOSFET.
SCHEMATIC DIAGRAM
This circuit, starting from the pre-amplifier to the final amplifier, almost all involve MOSFET-type transistors.
By using the MOSFET type, the supply in the final output circuit does not need to be too high voltage.
This is because the transmission from the MOSFET is already good.
In other word, a symmetrical 47 Volt supply will be able to produce an output until 300 watts.
This is cause the efficiency is already above 60%. or about 65 to 75%.
If we pay attention to the schematic in this amplifier, it appears that most of the active components of this amplifier use MOSFET type transistors.
I guess that the ADCOM itself or the engineers are planning to make this amplifier almost purely using a MOSFET-type transistor.
May be they are hoping that it will be more efficient and produce clearer audio.
In fact, we see here for the servo driver circuit, it still uses the MOSFET transistor too.
In the final output transistor using a MOSFET numbered IRF240 which according to the data sheet MOSFET. Its produces an output of up to 150 watts.
This means that if there are two pairs of mosfet then it is possible that the intention will be able to produce dissipation of up to 300 watts.