My HX Stomp broke down just the other day so I had to try the direct
MM sends CC 108 to BB
approach to control BB volume.
To be honest, it does work pretty well. It of course doesn’t have the flexibility that HX Stomp has with different function of exp pedal in each preset. But it does the job it needs to.
There were also some cons:
- The range mismatch of BB having values 0-100 but MM (at least in theory) should send 0-127. Thus part of the exp-range is missing.
- Voltage filtering wasn’t perfect. So when I wanted to leave the volume to 27% it started to wiggle between 26% and 27%. But not always.
- The case (2) above then blocked other commands to BB while volume was changing. This is most likely BB side design as I think it happened also when value wasn’t wiggling but volume was showing.
Luckily in the current set list there is no song that would require volume 27% (I’m assuming any value between 1-99 can cause this) and some non volume commands for BB at the same time. If there were then this would be much bigger issue.
Point 2 can be blamed for the cheap quality of Audio M expression pedal, but I’d be interested hearing if the more expensive pedals cause this with MM+BB. Or if others can even replicate this problem 
Any of the three points actually 
Note: the commands I tried in case 3 were the scroll up and scroll down, which is basically my emergency end without outro 
Didn’t test if other messages would be blocked or not 