BOSS ACA vs PSA Power adaptors - correctly powering your old BOSS pedals

 Boss & Roland compact pedals  & Synths were designed to use one of two adaptors: ACA or PSA.

ACA and PSA adaptors look very similar. They (and all Boss compact pedals) use the same sized jack/connectors but their electrical specifications and requirements are different.

 

ACA adaptor.: May be labelled 9V, but they in reality produce 12v's of "unregulated" DC power.

PSA adaptor : produces 9v's of clean, regulated power.

 

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Before 1997, Boss pedals usually used a ACA adaptor.

The ACA adaptor produces 12v's of "unregulated" DC power even though the pedals were designed to run off 9v's of DC power ( Many can use a 9v battery).

Unregulated adapters give a higher voltage at low currents. Eg a  Boss CE-2 draws just 8 mA.

So the ACA is really outputting 12V. 

These early pre 1997 pedals often had internal circuits that dropped the 12V DC to 9V 

(a simple zener diode and resistor inside the pedal converts 12V to 9V)

Around 1983, boss started to switch to the new system.

The  boss DD-2 (digital delay) was the first pedal designed around the new PSA adaptor. This produced 9v's of clean, regulated power. 

 

Boss used both of these power supplies side by side until 1997.

Finally they standardised all pedals to the PSA system.

 

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This PSA pedal supplies 500 mA of current to easily power multiple pedals, even digital ones.

 It's Centre -ve

The Roland PSUs are also centre -ve

My Boss RE-20 (reverb pedal) uses a 9V DC PSU. centre -ve. (500mA)

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 This is a PSA-120

The PSA-120 is designed for AC 117V (USA)

BOSS AC adaptors use these formats:

PSA - 100  for 100ACV (Japan)

PSA - 120 for 117ACV (USA)

PSA - 220 for 220 ACV (UK)

PSA - 240 for 240 ACV (Australia)

The PSA-240S is the recommended power supply for products including all new BOSS Compact and Twin pedals, ME-50/-20/-20B Multi-effects, the DB-66/-88/-90 metronomes, DR-Series drum machines, FC-Series foot controllers, MC-202, SH-101, SP-202, TR-626, and all TU-Series tuners.

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The ACA power supplies are designed for these pedals :

BF-2, BF-2B, CE-2, CE-2B, CS-1, CS-2, CS-3, DF-2, DM-2, DS-1, DSD-2, FT-2,
GE-6, GE-7 GE-7B, HM-2, LM-2B, NF-1, OD-1, OD-2, OC-2, PH-1, PH-1R, PH-2,
PSM-5, SD-1, TW-1, SD-1, SG-1, SP-1, VB-2 

These pedals work fine at 12V unregulated, but 9V regulated input does not provide enough voltage.

If your old pedal didn't come with it's original PSU there are a few solutions:

1. power your "old ACA pedals" via 12 volts

2.  put a 9V battery in it,

3.  modify your pedal. (bridge the zener diode and the resistor inside the pedal that converts 12V to 9V)

 

This is the rear of my Boss CE-2

There are 4 versions of the ACA power supply. 

 

This is a BF-2 (flanger)

It's a ACA version

 

 

 

 

 

 

 

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Roland Synthesizers & Drums

Roland SH 101 uses PSA-120, 220, 240 adaptors.

A 9V regulated, 500mA , negative-center adapter should work. 

 

According to the official manual, the Roland TB 303 uses a ACA 100, ACA220 or ACA40 depending on your country. negative-center. (Though I've used a PSA on another tb303 without any problems for years).

 

 To the left is my original TB 303 psu.

 

 

 

According to the official manual, the Roland TR 606 also uses a ACA 100, ACA220 or ACA40 depending on your country.  negative-center