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The PSA adapter is a regulated power supply that outputs 9V DC and can supply up to 200mA current. Regulated means that the power supply contains a circuit that helps stabilise the voltage at 9V even when the load is increasing. The earlier ACA adapters did not have this feature and when many pedals were connected, the voltage would drop.
Like the ACA adapter, the PSA adapter is available as PSA-100, PSA-120, PSA-220 and PSA-240. The number reprsents the input mains voltage it is designed for.
Powering ACA pedals with a PSA power supply
Powering the older pedals designed for the 12V DC ACA adapter PSA adapter will not work very well. The older pedals contains a resistor and diode that will lower the internal voltage voltage supplied to the rest of the circuit. This will prevent the pedal from beeing fully powered and its LED will often fail to light up properly. The solution is to use a daisy chain and plug in another pedal designed for the newer PSA adapter. The lead between the two pedals will short the resistor diode pair and the pedal will receive full power.