Boss FV500 Expression with Duo X

Hi everyone,

Hope I’m posting this in the correct forum. (Admins, please move it elsewhere if not.)

I’m trying to get the pedal above to work with the Duo X, with no luck. I’ve been through a number of posts (like this one and others) and the wiki pages. My MOD input is set to EXP and I’ve tried signal on tip and ring.

I get a floating reading between 0 - 0.02 V throughout. If I disconnect the pedal, that is what I get too.


(It just keeps going up and down, randomly).

My pedal has a 10KΩ resistance. From Boss’ website I could find not information on polarity, but I’ve tried both anyway.

I’m using TRS cables and tested this same pedal with another hardware unit – it is working fine.

Is there something I’m missing? Maybe my unit is faulty? It reverts to CV when I pull the cable off, but if I understand correctly this is a security measure, am I right?

Any help is appreciated.

Hi. I had the same problem with my expression pedal. I tried all possibilities and suddenly it worked. All I have change is that load a cv meter on my pedal board.
Now it works all time with no issue since 4 month.


:astonished: :astonished: :astonished: :astonished: :astonished: :astonished: :astonished: :astonished: !!!

It was this simple?


I had it connected to the CV Meter (image on previous post), but after I connected the meter to something else… it worked!

Thanks a million, @Julien! :heart_decoration:


I think it’s a bug.


Thanks for reporting this @QuestionMarc and @Julien.
Indeed this really looks like a bug. I will report it to the guys.