Boss ACA power question?

[soggybag]

I have an old Boss BF-2. It has the ACA adapter sticker next to the power supply. I guess it's meant to run on 12v ACA power supply.

The article below points to a diode and resistor used to reduce the power from 12 to 9v. The article mentions that the LED won't light from a 9v supply unless it's daisy chained with another pedal. Mine does exactly this, if it's the only pedal in the chain the LED won't light, if I add another pedal to the chain it lights. What is happening here?

Adore anyone know if these pedals operate normally from a 9v supply if there is another pedal in the daisy chain? Or should they still be run from a 12v supply? I have always used a 9v supply and the pedal works, maybe I'm just not hearing at it's best?

https://stinkfoot.se/archives/1019

[Rob Strand]

Suppose you run two daisy-chained pedals, one non ACA and one non-ACA (ie. PSA or other), off the same supply.
The non-ACA pedal has its audio ground and 0V from the power jack shorted together.

When you daisy chain the pedals the audio grounds of the two pedals are connected together.   That means the 0V (ie. the PCB 0V) of the ACA pedal has a direct connection to the power-supply 0V via the path of the audio ground and the DC jack of the non-ACA pedal.   In effect the daisy-chaining shorts out the diode and resistor network,   That means you can run a 9V regulated supply on both pedals and both pedals will see the 9V.   The pedal ordering doesn't matter.

Normally, without the diode and resistor shorted out the ACA pedals will need a 9V unregulated supply which is 12 to 13V in order for the PCB to see 9V.     If you were to daisy chain two ACA pedals the 0V is not shorted and you still need a 9V unregulated supply for both pedals to see 9V at the PCB.    A full ACA pedal system works fine.  In fact it works fine without ground loop problems.


Many ACA pedals will work OK from a regulated 9V - perhaps with a little loss of head-room.   They will definitely work better with unregulated 9V.