Indeed – in normal mode it has a stereo (TRS) jack, which is compatible with a TRS volume pedal, while in split mode the H9 offers a mono (TS) jack, which will give 0-100-0 when used with a TRS volume pedal.

I’m not familiar with Dunlop X. Hopefully its manufacturer of one of our other users can help.

Ernie Ball Junior 25K is one we recommend – note that you must plug into the socket marked “OUTPUT.”

Please also read out technote https://www.eventideaudio.com/support/downloads/using-both-aux-switch-and-expression-pedal-h9

“Further, many Volume pedals have too high an impedance, meaning that the pedal will only operate over part of its range – the impedance should ideally be between 10K and 25K.”

“Be aware that many expression pedals are hugely over-complex things which can be hard to set up.”

nickrose – I quoted these two parts from the technotes. Would an ideal expression pedal for the Factor Pedals and the H9 be a pedal with a 10k potentiometer and a single TS output? 

joszwa80 – I have been using the Ernie Ball Junior 25K and can verify that it does work. I am also having success controlling two Factor pedals or one Factor pedal and one H9 simultaneously with the 25K Stereo Volume Pedal. It has some quirks though. For that reason, I would recommend starting with the Ernie Ball Junior 25K.