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P50 Classic (1966 ‘Black Flag’ Plexi)

50-Watt Park w/ Tube Rectifier

The Park P50 circuit with tube rectifier and EL34 power tubes is ‘Warm but aggressive’ (Warmer tube saturation and tighter filtering than the original P45). Legendary EL34 power tubes add colour, and focus in the mid frequencies, while a tube rectifier provides a bit of ‘squish’ or compression when the amp is pushed. The Park P50 (“Black Flag” Plexi) nails the bite and aggression that players like Angus Young love and the EL34 power tubes have played a large part in creating the de facto ‘British Tone'. Two differently voiced channels (one brighter) add flexibility and player/guitar options. Since the Park P50 has the early version of Jim Marshall’s 50 watt plexi circuit, the bright channel still gives you plenty of bottom end so you do not have to jump channels for a full sound.

Mitch Colby has added two push/pull pots for greater flexibility - one is an upper mid boost that affects both channels - the other applies independent bright cap values to both channels simultaneously - a more ‘brilliant’ design feature? Of course it’s a Park!

This tube rectified amp now comes standard with PPIMV (Post Phase Inverter Master Volume) which allows the artist/player to overdrive the P50 at lower volume levels - or crank the Master Volume to effectively remove from the circuit!


  • — Park P50 - Classic ‘British tone’
  • — The EL34 power tubes add ‘colour and focus’ in the mid frequencies.
  • — Tube rectifier provides a bit of classic compression (squish) when the amp is pushed (only used for a short time on the vintage Park P50 amps making them desirable, rare and collectable)
  • — `Black Flag` circuit - famously collected by Angus Young.
  • — Two channels (one voiced brighter) and 4 inputs offering tonal flexibility while maintaining full bottom end.
  • — 40 Watts clean, 70 Watts cranked.


  • — Push-pull pot 1 - upper mid boost across both channels
  • — Push-pull pot 2 - applies separate value bright caps across both channels
  • — PPIMV.- Post Phase Inverter Master Volume now standard - overdrive the Park P50 at lower volume levels - or crank the Master Volume to effectively remove from the circuit as in the original Jim Marshall Park P50 design.
The PPIMV is a volume control after the signal is split by the phase inverter tube and just before it goes into the power section (tubes) of the amp. Because the PPIMV comes after the phase inverter tube it benefits from a little more added ‘overdrive’ when compared to the PrePIMV.

A neat trick with the PPIMV is that by cranking it you are essentially ‘taking it out of the circuit completely’ and hearing the amp without a Master Volume which only became available in later models.

Technical Specifications