Akai MPK mini m2 - no note off in standalone mode

#1

I have an Akai mpk mini 2, and everything works fine in monophonic. The polyphonic examples and also some simple stuff i made work also as expected in Live mode. But when i Upload the Patch to SD or internal flash the notes seem to be stuck: the gate doesnt seem to turn off anymore. this only happens for the keys of the mpk , when y set the pads to a different midi channel there is no problem. Midi monitoring shows note on and note off, but the note off doesn´t seem to be registered. How is Live Mode different than uploaded? what can be the problem?
Thanks if anyone can help me.

Michel

#2

there should be no functional difference. can you try and start the axoloti with the controller disconnected from the usb-port and once it has completely booted you attach the akai. does it work then?

#3

no, that makes no difference, but what i found out that if i plug a jack ( just an adapter, not connected) into the sustain in of the mpk it works.. so it seems a problem is related to the sustain? not shure how this is implemented in midi, but a good workaround for now.. Still strange that it only hapens in standalone mode..

#4

i would rather guess that something is "wrong" with the akai. how do you power the axoloti when standalone? differently then when connected to the pc?

i have seen weird problems with sustain jack inputs on different synths and midi controllers. maybe something weird is going on in the akai, when it receives a little different power. can you power the akai with an additional power supply? how does it act then?

#5

tryed a different options , just connected to the PC, or to a 9v 12v source, doesn´t make a difference. just found out the sustain workaround now by accident.. gona do some more testing, but yes something wrong with the akai is also a possibility. Gona try it on a different software or hardware, hav´t done that as it is new..

#6

So, it seems the MPK has a "reversed" sustain behavior, on by default. I hooked up a pedal and can reproduce the faulty behavior by pressing the button, also in Live Mode. Only difference is that in Live Mode the initial Status isn´t transfered to the patch, so it doesnt know the sustain is on ( probably because its not restarted completly). Pushing the Sustain Button twice and it shows the same behavior in Live Mode.

So problem solved for me, Probably possible to code a custom object for this behavior, but for now i just put a jack in.

Thanks for your support

#7

hmm, still seems odd that this would be on by default. sounds like a bug to me. maybe on yours the jack plug somehow shorts when nothing is connected? (some of those plugs have switches on the contact, that are only open when you insert a cable) maybe some of that circuitry is broken...

Polyphonic patches chord playing gives stuck notes via USB midi
#8

yes, i opened it, the contact is also a switch, i bended it slightly so it doesnt close in normal position but still makes contact when the jack is inserted, not shure if if was supposed to be like that , but it works now.

#9

This really seems to be the case. I just tried it using MidiOx: The first message is from pluggin in a 1/4 cable, the second one is from removing it again. So I guess that supports the hypothesis that the switch (for normalizing the input) is connected to something it should not be connected.

Opened MIDI Input
000013CE   1  --     B0    40    00    1  ---  CC: Pedal (Sustain)
00002041   1  --     B0    40    7F    1  ---  CC: Pedal (Sustain)
#10

Great, thank you for the tip. I made some photos that hopefully will help others with this issue:
The TIP of the sustain pedal jack is supplied with 3.3v, the rest is connected to GND (=ground=0v). When the pedal is pressed, the tip is pulled down to GND. Now each of the contacts in this jack socket has a switch, so that the device could detect whether a jack is plugged in, or use some normalized signal path. The problem now seems that when no jack is plugged in, the tip also gets pulled to ground. Usually this is not a problem, as the sustain MIDI signal only gets sent when its state changes. For some reason it seems that when using the axoloti, the sustain signal gets sent at the very start.

So what are the possible solutions?
1. Use a sustain pedal OR
2. Plug in a 1/4" to 3.5mm jack converter (or a cable connected to nothing else)
3. Make a small modification to the jack of the Akai MPK mini (II) which is what this guide is about:

To make this modification you just need some needlenose pliers (or any pliers with a pointy end), and a small phillips head screwdriver. On the underside of the MPK there are 12 phillips head screws you can unscrew. Then you can carefully pull the red and the black halves apart. Make sure you don't just rip them apart as there is a ribbon cable between the two. There is also the usb-socket on the side that needs some fiddling to get out.

To make work a little bit easier you can unplug the ribbon cable: To do so you have to pull the two tabs on the side of the board mounted connector out by a few mm, as displayed in the left picture.

20200904_224928.jpg3784x2128 547 KB

Then you can take the pliers to bend the last few mm of the tip-contact of the jack socket up. The goal is that there is a small gap between the tip contact (which is supposed to be at 3.3V when the device is powered, and the contact is disconnected), and the switching contact (which is at 0v) - see right picture.

Now you just need to plug the ribbon cable back in, push the two tabs back in, reassemble the two halves and put the screws back in. (Make sure you just reverse the screw until you feel it falling into the threads, and only tighten them then. Otherwise you cut new threads into the holes which just weakens them.)