EHX B9 Mod (Expression pedal input)

[diegofresh]

Hey guys,

I am looking to add an expression pedal jack to my EHX B9 pedal to control the modulation speed.

https://www.jhspedals.com/products/mod-shop/electro-harmonix-b9-expression-mods/

https://www.youtube.com/watch?v=3_OzYTXy-iY

Do I just need to swap the pot on the mod knob and wire a TRS jack to it?  Any guidance would be appreciated....

[FUZZZZzzzz]

I would connect them both to a switchable jack. So when theres no plug inside the exp pot you can use the mod knob and visa versa.

[diegofresh]

I would connect them both to a switchable jack. So when theres no plug inside the exp pot you can use the mod knob and visa versa.

Actuary there won't be an expression pot. Just a 1/4 jack, which could have something similar, right?

[anotherjim]

I would say the existing panel pot has all 3 terminals wired to the switch contacts of a TRS switched jack. All 3 of the plug contacts of the jack are wired to the pcb in place of the panel pot. With no expression plugged in, the panel pot is connected via the switch contacts to the pcb. With the expression plugged in, the panel pot is disconnected by the switch contacts breaking and the pot in the expression pedal takes over.

You need to know how the pot in the expression pedal is wired to its TRS plug. Usually, the minimum end of the pot is Sleeve, but there are pedals out there with the pot wiper going either to the Tip or Ring. Also identify how the panel Mod pot is wired. Set it to minimum and measure resistance from the middle (wiper) contact to either end contact. The lowest resistance end to the wiper will wire to the new jacks sleeve.

[FUZZZZzzzz]

Exactly as how I wanted to explain, but didnt 

[pgiorgio61]

Hi there... (if still there!)
I have made some modification on my B9 (OLED display...) that include a different use of the foot switch: keeping pressed it speed-up the Leslie, like any real organ player like!
Have a look: https://www.instructables.com/id/B9/