Park P50M

The P50M is the first split-cathode amp Jim Marshall built. The change reads as small and is large in the room: channel one becomes significantly brighter and cuts through a band mix instead of sitting behind it. Increased filtering came with it, stiffening the power section and making the amp respond faster to the pick.

This is the circuit that went on to define seventies rock, and it is the sound most people are actually describing when they say Park or Marshall. It also sits exactly midway in the line, after the Park 45 and before the Park Master Volume with its cascading channels and master control. Four inputs into two channels, jumpable for more range and saturation; a pair of EL34s behind a solid state rectifier; PPIMV as standard; and Mitch Colby's push-pull upper mid boost and push-pull bright caps working across both channels.