Marshall 20W Schematics

In 1967 Marshall introduced the 20W amps as the successors of the 18W amps. They didn’t sound as good as the original 18W amps though. These amps use 2x ECC83 in the preamp and 2x EL84 tubes in the power amp and a solid state rectifier in the power supply. They were discontinued around 1974.

JMP 1917 PA 20, 20W head & two 2x 13″x8″ cabinets

This set consisted of the 1917 20W head amp and two speaker cabinets each with fitted two 13″x8″ eliptical speakers. This amp had 2 channels and 4 inputs.

Schematic with 2x ECC83, 2x EL84, (Marshall).

Photograph of a 1917 PA 20 from 1973.

JMP 1958 Lead, 20W 2×10″ combo

JMP 1973 Lead & Bass 20, 20W 2×10″ combo

This model was built both as a head (with a 1×12″ cabinet) and as a 2×10″ combo.

Photograph of a 1973 Lead & Bass 2×10″ combo (thanx to Scott!).

JMP 1973 Lead & Bass 20, 20W head with 1×12″ cabinet

This model was built both as a head (with a 1×12″ ported cabinet) and as a 2×10″ combo.

JMP 1974 Lead & Bass, 20W 1×12″ combo

JMP 2019 Bass, 20W head with 4×10″ cabinet

Schematic with 2x ECC83, 2x EL84, (Marshall).

JMP 2022 Lead, 20W head with 4×10″ cabinet

Schematic with 2x ECC83, 2x EL84, (Marshall, 1969).