I've been using an AKAI APC mini for about 6 months now to control various parameters. I have way more parameters to control than faders that the APC mini has (only nine), so I built a small external to switch between "scenes" of the faders, so I could control as many as I need.

I find that occasionally the controller will update the value of its faders without actually touching it. This wouldn't be a problem if the faders were permanently assigned to one and only one parameter, but since the assignment is constantly changing, the updated value potentially messes up an entire scene, especially since I'm not even touching it.

Has anyone experienced a similar issue? Is it something to do with midi controllers in general? Or with the way Pd interacts with the controller?

Obliged.

@afsacp Hi. I own the sister product to yours, the MPK mini and I have not experienced these types of issues.

Are you receiving any other MIDI data that could be routed accidentally to your parameters? Could you post your patch or explain how you are controlling the flow of MIDI to your parameters?

Any controller that derives a digital value from a scanned analog potentiometer can potentially have this kind of problem. The higher quality devices may drift up or down a single increment due to small voltage fluctuations that happen when the pot is "too close" to the next increment.

The low end stuff is worse since they use the flimsy cheapo pots that may not only be less stable but also outright defective and prone to jumping values all over the place. I would tend to put any recent vintage Akai gear (i.e. post Akai Japan ownership) in this category and that's the reason I always warn people away from it.

@afsacp Hi,

I don't think it is PD that is causing the problem (verify this by downloading a midi monitor program)...

I have also this kind of behavior from one of my midi faders / knobs controller. You can try to use a contact cleaner.

You can also try to use pd-extended with the mapping abstractions ([iir], [median_7], ...) to supress noise. If the value is not changing but only outputting the same value you can use [change].

Good luck,
Cheers~

I would be very careful about using any type of contact cleaner on the controls as this can often do more harm than good. However, if it is just a dust issue you can try techduster/compressed air as a safer alternative.

As said the problem you are having is common and may or may not have anything to do with a malfunction -- it's often just a limitation of using that type of controller hardware.

The usual solution (especially with the sort of software control switching that you are doing) is to use a controller with digital encoders instead of pots, The endless turn type along with "snap to value" motorized faders are preferred to deal with the problem of absolute physical control positions vs. the switched relative values that are being adjusted.

Thanks all for the great answers. @EEight, I downloaded MIDI Monitor, and used it both with the patch and without it (but with Pd open). In both cases it reported messages from controllers that were not being touched. It seems the issue is, as @NoDSP suggested, the quality of the device. I have another controller, a Samson Graphite M32, hooked up, and it doesn't seem to send any undesired messages, so that would confirm it. I do remember the AKAI being on sale at Guitar Center when I bought it... I'll try with the mapping abstractions suggested by @EEight. In any case, this was tremendously helpful.

I'm not sure how much better or worse the quality is between the Akai and the Samson, but I would expect the M32 to be less problematic simply because it's only got two pot controls (I'm assuming those are pots and not encoders) compared to the APC's nine. More mechanical pots means more potential for that kind of spurious signal generation. Momentary buttons, keys and touchstrips aren't known for those sorts of issues unless they're really messed up.