There are two channels within the Tube Drive section, and one clean channel. Marshall 20w bass amplifier schematic, marshall 20w lead amplifier. Marshall Diagrams, Schematics and Service. It delivers 100 watts of solid-state power at 4 ohms. The Marshall Lead 100 Mosfet has a solid-state power amplifier with a tube pre-amp through a 12AX7. The Clean section is only solid-state, whereas the 'Tube Drive' section delivers exactly what it says - tube like tone out of a hybrid head amplifier.
