Park P45 Classic (1964-66)

The P45 Classic is the original Park circuit Jim Marshall drew from the Fender 4x10 Tweed Bassman - the amp everyone else calls the Bluesbreaker circuit, here without tremolo. A pair of KT66 output valves gives it the rich, open character that made those mid-sixties records sound the way they do: clean and complex at low settings, and dense and singing when you push it. A GZ34 valve rectifier sits behind them, and the sag it introduces when the amp is driven hard is where the compression and the playing feel come from.

Four inputs into two channels give you the usual options - one channel, the other, or both jumped for a thicker blend - with shared three-band EQ and a Presence control across them. Park now fits PPIMV (Post Phase Inverter Master Volume) as standard, so the power section can be driven at a volume that will not clear a room; crank the master fully and it drops out of the circuit as though it were never there. Mitch Colby's push-pull brightness pot on channel two volume opens up what was traditionally the dark channel, which makes it usable with far more guitars and pickups. Impedance is selectable at 4, 8 or 16 ohms on the rear panel, and it wears the custom vintage banana knobs.