1986 BOSS PSM-5 Power Supply and Master Switch

Model Description:

Introduced in 1982, the bright red Japanese BOSS PSM‑5 Power Supply & Master Switch, is not really an effect pedal per se. Up to the 1980s, effect pedals tended to be simple daisy‑chains with guitar at one end and an amp at the other with any number of pedals in between. As pedal boards became more complex there was a growing need for both a reliable power supply for multiple pedals as well a flexible means of routing the signal direct or through a number of pedals. The PSM-5 was an early attempt to cater for these more demanding situations, becoming an integral part of many musicians’ setups. Nowadays, it seems a relatively archaic way of doing things compared with modern sophisticated power supplies and compound switching systems. The PSM‑5 was the first BOSS power supply in their typical compact pedal format. Not only can it provide 9V power to up to seven BOSS (or compatible) 9V pedals but also it acts as an effect loop switch. When the loop is switched off, the signal is passed direct from the input to output jacks. When the loop is switched on, the signal is passed from the input to the Send output which can be connected to any number of effects before being routed back to the Return socket and then to the (Amp) output. There were not many competitors at the time, the nearest probably being the Electro‑Harmonix Switchblade, which was a simple A/B channel selector. On the vintage market, the PSM‑5 is currently both plentiful and cheap, so it may just fit the bill on a vintage pedal board.

Pedal Description: In the basic guitar rigs of the 1960s and 1970s, the BOSS PSM‑5 may seem OTT or a bit of an irrelevance. In hindsight, BOSS’s solution seems quite prescient, filling an emerging niche in the market and proving the concept for modern‑day pedal board tools. At its most, the PSM‑5 fulfilled two main functions. One use was to cut down on the need for large numbers of batteries and/or wall‑wart power supplies. The other use was to route a signal through an effect loop or to bypass the loop altogether. It is worth mentioning that it is the loop that the PSM‑5 switches, not the individual effects in the loop, which need to be operated in the normal way. Alternatively, it can also be used as a straightforward A/B channel switch with one input and two outputs. Being objective, all the PSM‑5 does is to pass a BOSS PSA 9V power supply through the pedal, whereas, it could easily be daisy chained direct (and it doesn’t provide for pedals requiring the more powerful BOSS ACA adapter). As a switching unit it is also pretty rudimentary by today’s standards. Depending on who you listen to, the pedal has either a zero or marginal impact on sound, so it may or may not be completely neutral. However, any slight signal compromise may be worth it for the extra utility and flexibility gained. In use, it’s pretty innocuous but does what it was designed to do with little fuss or bother. This example, dating from November 1986, is in great original condition and works just as it should. Time to switch?


  • Made in Japan by Roland Corporation in 1986
  • BOSS treadle footswitch turns the effect loop Send/Return on and off
  • LED ‘Check’ light to indicate when the effect loop is in use (red for on and green for off)
  • ¼” input (Guitar) and output (Amp) mono jack sockets plus ¼” effect loop Send and Return mono jack sockets
  • External 9V DC power supply input  (no internal battery facility)
  • 9V power supply out for up to 7 other BOSS pedals (PSA powered)
  • Red ‘Made In Japan’ label on the base of the pedal
  • Dimensions: 70mm (w) x 125mm (d) x 55mm (h)
  • Weight: 340g
  • No box or instructions

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