I tried a few things before leaving for dress rehersal.
1 made sure the mc8 was not in looper mode, i don’t think it can be in looper mode on startup, but had the nagging doubt.
2 tried the various sensitivity settings, no joy.
3 tried the other ports, same result
4 finally polarity switch on the back of the pedal. Was set to 2, switched to 1, recalibrate.
The strange thing is i had the same issue with the m audio exp pedal, will have to check if it also has a polarity switch.
I made all these changes before testing in gp, what i noticed was that without gp running, the readout of the expr ped in the display of the mc8 was irregular. This is why I kept trying various fixes before opening gp. Ie, the readout said 0 in heel pos, then it had a rather erratic travel and when releasing the pedal anyway in mid travel, the numbers kept changing up and down in the display.
However when opening gp the numbers on the display were normal, meaning stable and not jumping up and down.
Bass plugged in and volume is once again smooth.
I am suspecting the polarity switch, which is the complete newbie rookie amateur thing to overlook, and i’m kind of blushing to admit this here.
One thing to learn from this is how difficult it can be to troubleshoot stuff during rehersals or soundcheck.
I’ve had a couple of issues on previous soundchecks regarding balancing levels to foh and other things, i could not solve them on the spot, you know, collegues “patiently” waiting while my shoulders travel higher and higher. Then at home i solve the issue after 1 minute…
Moral for me is permanently patched cables on the soundcard, front access to properly labelled xlr plugs on a patchbay(no more remembering specific trs to male/female xlr…) and now always doublecheck polarity of pedals…
Thanks for the input, have a great weekend!