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Expression pedal only travels 0-40%

gdgross

Veteran
hi all - I'm using an external expression pedal as my volume control / it's assigned to a vol/pan block that I have after the amp in every patch.

I noticed tonight that when I went to calibrate it, the ax8 only moved from 0 to about 40% of the way up. That's ok, I just assume the pot isn't going through its full motion inside the pedal.

The strange thing is when I observe the volume in the block, it also only goes about 40% of the way up. Shouldn't calibrating the pedal teach the ax8 that when it reads 40% of the pot reading, that's 100% of the movement, and correlate that to full scale volume?

Thanks,
Geoff
 

ethomas1013

Forum Addict
Yes, that's the way it should work. I had an expression pedal that only ready about 70% when calibrating but it did go to 100% in the AX8 when assigned to an effect. Something is not right...
 

philipacamaniac

Fractal Fanatic
It needs to reach a minimum percentage of travel for the calibration to work.

40% sounds like something isn't wired correctly. Is it an expression or a volume pedal? TRS jack or using a TRS to dual TS adapter?

EDIT: more specifically,

The calibration requires a difference of at least 0.75.
 

gdgross

Veteran
Could be a wiring error, but I'll have to dig into it to check. The strange thing to me is that the volume doesn't go all the way up on the controller even after calibrating the pedal with its 40% travel.

The pedal is an EB jr, which I've opened up and changed to a linear pot to use as an expression pedal instead of volume. Although ironically I'm using if for volume with the ax8 and have the controller curve set to log.
 

joe rogers

Forum Addict
Could be a wiring error, but I'll have to dig into it to check. The strange thing to me is that the volume doesn't go all the way up on the controller even after calibrating the pedal with its 40% travel.

The pedal is an EB jr, which I've opened up and changed to a linear pot to use as an expression pedal instead of volume. Although ironically I'm using if for volume with the ax8 and have the controller curve set to log.
There is not enough travel in your pedal (0% - 40%) to complete the calibration.
 

brokenvail

Fractal Fanatic
Could be a wiring error, but I'll have to dig into it to check. The strange thing to me is that the volume doesn't go all the way up on the controller even after calibrating the pedal with its 40% travel.

The pedal is an EB jr, which I've opened up and changed to a linear pot to use as an expression pedal instead of volume. Although ironically I'm using if for volume with the ax8 and have the controller curve set to log.
with an EB pedal you would have to use a y cable to use it as exp
 

gdgross

Veteran
Hmm I am indeed using a y Cable...perhaps the pot is not spinning enough inside the pedal. I'll have to bust out the multimeter and see.

If that's not it then it's gotta be a cabling problem right?
 

DLC86

Forum Addict
Hmm I am indeed using a y Cable...perhaps the pot is not spinning enough inside the pedal. I'll have to bust out the multimeter and see.

If that's not it then it's gotta be a cabling problem right?
Have you tried swapping the plugs on the pedal side?
 

Rex

Legend!
...perhaps the pot is not spinning enough inside the pedal. I'll have to bust out the multimeter and see.
EB pedals that have been restrung sometimes don't swing through their full range. It takes some fiddling around to restring them properly
 

Jarick

Inspired
I had the same issue with a new Mooer pedal. It randomly started working properly after a few days. I literally tried everything I could think of and nothing worked, then one day it started working on its own.
 

Lecchu

Regular
Recently I did an express pedal using old unused Dunlop Gain (volume) pedal, from which I threw all the contents from inside. I had a similar problem:

I used a linear 100kOhm potentiometer. When folding the pedal, the "tooth" stripe was accidentally inserted so, that the potentiometer range was between 25 and 80kOm. in this case AX8 - even after calibration - still saw in the preset range of changes from 20% to about 80%.

When I corrected the "tooth" stripe that the expression pedal was running from about 0 to 55kOhm - then it started working properly (ie, during the calibration, AX8 saw the range from 0 to 55, but the preset was already 0-100%). So I think it may be important that the potentiometer works from about 0kOhm point (and up).

Another thing, in my opinion, it is not correct, that the TIP from JACK socket should be conected to the top ("full range") of the potentiometer and RING is to return (AX8 manual, page 21):
"Expression pedals require TRS cables because full voltage control is transmitted to them on one contact (the tip), while less than full voltage is returned to another (the ring) so the host device is able to sense and utilize the pedal position. "

In my case, the expression pedal started to work correct only when the full range (top of potentiometer) is connected to RING in JACK socket and the return of potentiometer position is connected to TIP.

Maybe someone will help my experience.
 
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