MIDI sync issues

OP-1
#1

Hey guys, I’ve been trying to sync my op 1 to the digitakt via midi, but I noticed it got out of sync pretty quick. I kept an eye on the tempo on the tempo screen of the op 1 and noticed the tempo was moving up and down like .1 bpm. If I sync up the digitakt to be the master, the op 1 also appears to change up its tempo in the same fashion.

I tried syncing up the op 1 to fl studio and had the same problem, so I’m pretty sure it’s an op 1 specific problem. Anyone have any similar issues?

#2

Does it sound out of sync also? Or just the BPM is fluctuating? BPM is not communicated via MIDI, so the OP-1 would have to calculate it based on the clock coming from somewhere else. Maybe there is enough slop in the calculation that it fluctuates. But if it doesn’t sound out of sync, then it could be ignored as just a math issue.

#3

Hope it’s not a dumb question but: are you using a MIDI USB host between them? I don’t think you can directly plug the two together with a MIDI-to-USB cable

#4

I don’t ever send the op clock anymore, it was too unstable as a slave in my experience, I always use it as master when it’s in my set up

#5

the problem of clock timing runs pretty deep - there are two major issues


1] midi clock needs to be very, very, stable. It is sent at too low a resolution (24 of these from one beat to the next). There’s the sending half and the receiving half of this problem - the device sending clock must have it implemented so no other function ever interferes with when the clock pulse (midi message) goes out. When the clock master device also plays audio, and allows you to edit things on a display, it could get messy. The receiving half is subject to timing issues as the message travels - the weakest link is usually the MIDI<>USB boundary, but also USB<>USB (!). Old USB interfaces/controllers/devices generally have worse timing performance.

2] then there’s the OP1 tape, on which one has a looped segment that they expect to loop in sync. If we’re doing this in similar ways, I go to a beat marker, loop in, then to the next, loop out, and loop-play the section. The problem is hard to see, but as the clock drifts, and this is where a DAW differs significantly, the OP1 keeps the loop length the same, i.e. the same number of samples. A DAW, in comparison, would adjust the loop points because they’re marked in beats and bars, not sample rate samples, so the loop length may change and all MIDI played would still sound in sync. With DAWs like Ableton that stretch audio, the audio also sounds in sync. In fact, if the timing changes are small, the adjustment of the loop boundaries would have you not notice the issue with non-stretched audio, but on a DAW the adjustment is continuous and always applies. On the OP1 there is no adjustment. It loops, then it’s off, so it loops when the loop ends, not when “it’s time to loop”.

Unless the OP1 starts dealing in tempo ticks, which I doubt it ever would (, but one can dream!), you’d need to move mountains to get it to play nice as sync slave. Using it as a master would be assuming that it itself doesn’t mess up its own timing, especially as it tries to smooth audio over the loop points. Something however tells me that it does.

So, contrary to all reason, monkey-sync by just keeping the same BPM actually ends up being more reliable. :expressionless:

1 Like
#6

I use op and ot, op as master and It stays in sync perfectly every time. I can even hit stop on tape, scroll thru tape with arrows or encoder and hit play whenever and it’s still in perfect sync, as master using MIDI