Help! MIDI Clock Sync & Tempo Drift Issue

i’m a I long-time Cubase user and I’m banging my head against a wall over some MIDI Clock issues with my current rig. I’m running Cubase 7.5.20 64-bit on a modern Windows 7 64-bit PC with an Edirol UM-880 MIDI adapter. I’ve always used Cubase’s internal clock to sync external devices (synths, effects, etc.) but I started running into issues when I tried to sync a DSI Prophet 12 Module to MIDI Clock.

Whether slaving the P12 to MIDI clock over its USB MIDI connection or DIN MIDI with my Edirol, I can’t get the P12’s delay lines to sync with any consistency. When Cubase is set to 120BPM and the P12 is slaved, the P12’s tempo display vacillates +/-3BPM, and when the perceived tempo changes the delays react by warping and warbling so oddly that the delays effectively can’t be used. A few more interesting observations:

  • I have Cubase set to pass MIDI clock when stopped, and the drift is mild when the P12 isn’t receiving any direct MIDI data (i.e. note ons/offs); it sits at the prescribed MIDI clock tempo with brief, intermittent deviations. But when I play notes or the DAW plays back notes, the P12’s clock deviates more rapidly and substantially. You can watch the P12’s tempo indicator change as a direct result of notes being played. The more notes and the faster played, the faster the tempo moves between values.
  • The clock issues almost disappear at lower tempos 80 and below, and they are much worse at higher tempos (deviations of +/-6BPM have been observed above 200BPM).
  • Oddly, the P12’s arpeggiator seems to maintain sync even when the delays freak out. I have a long-running ticket open with DSI and they say the MIDI clock for the arp and delays are derived in 2 different ways. They also assure me that they are certain that the issue is coming from my DAW/Cubase, which brings me to…
  • Other devices show mild deviations in MIDI tempo, but nowhere near what I experience on the P12. I have a couple Eventide pedals, for example that show occasional tempo deviations of +/-1BPM at most, but they generally sound tight at 120BPM. Similarly, my Bass Station seems to sync up with no problem at 120BPM and it, too only shows occasional and minor tempo deviations +/-1BPM at most.
  • I tried migrating the Edirol’s USB connection to a different cluster of USB ports on the PC and I tried USB 3.0 and 2.0 ports just for kicks – no change.
  • I also disabled MIDI Clock output to every device but the P12 – no change.
  • I hooked up the DIN MIDI input on the P12 from the thru port on an Eventide pedal that receives MIDI clock from Cubase via the Edirol. Switching back and forth between USB MIDI and DIN MIDI as clock sources, I believe the clocking is perhaps somewhat more stable over the DIN MIDI input – there’s less frequent deviation and milder swings in tempo (mostly +1/-2) – but still not usable for long delays because of how oddly the delay output warbles and warps as it tries to adjust to the drift on the fly. Maybe the Eventide is “stabilizing” the issue for the P12 to some extent?

DSI swears up and down that what I’m seeing proves that I’m having MIDI Clock issues, though I’m still somewhat skeptical given that other devices seem to sync to MIDI Clock with repeated success. The fact that the P12’s delay sync struggles whether using the Edirol connection or its own USB MIDI connection suggests that the Edirol is not the culprit, so now I’m looking at Cubase to see if it might be the issue (DSI is fairly certain it is). Note that another user on Gearslutz (where I started researching this issue) was able to repeat the issues using his P12 and Cubase 7.5.20. A very specific interaction between Cubase and the P12 perhaps? Seems unlikely, but who knows.

Are there any sure-fire ways to identify/measure MIDI Clock issues? Any other suggestions? I’ve spent a lot of time on this and it’s fairly frustrating. I’d like to rule out any Cubase issues, if possible, before talking to DSI support again.

Thanks in advance for any ideas, suggestions or other input!

Unfortunately you find yourself in the classic situation where one vendor blames another, and you’re faced with the task of _dis_proving a sweeping statement they’ve made with no evidence whatsoever presented to back it up. If I were cynical I’d suggest that maybe DSI want you to go away for a few months at least while you figure out some way to set up a test rig to do what should effectively be their job.

If they’re so adamant that Cubase is the issue, apart from asking them whether they’ve brought the issue to Steinberg’s attention (which I’ll bet they haven’t) then the best thing to do is to eliminate Cubase from the equation entirely by using something they can easily replicate, for example use MIDI-OX to send MIDI Clock.

For the record:

Yamaha Motif Rack
Roland DC1
Roland XV5080
Korg Triton Rack
Korg Triton ProX

No issues with midi clock here as far as sync goes. I only make one port active since midiclock is a global command as far as my MOTU MTPAVUSB goes. I think the P12 is the issue. I sync all those synths here BTW

That said, Im not on PC, could be an issue there

Thanks for the replies, folks, and for the suggestion of using MIDI-OX to generate MIDI Clock as a test vehicle.

DSI asked that I try using a different DAW, but I’ve been a Cubase user for so many years that I don’t have anything else loaded and I’m not interested in loading a trial or light version of anything else on my fairly pristine PC. I have MIDI OX installed, but I didn’t think to try it as a clock source. I will also test using one of my Eventide pedals as a MIDI Clock source.

The fact that the P12’s sequencer seems to sync tightly (along with several other devices) whereas the P12’s delay lines don’t still suggests to me that it’s a P12 issue, but they’re adamant that what I’m seeing on the screen (fluctuating tempo indicator) is a clear signal of a MIDI Clock issue from the source.

One more question to clear the air: when y’all sync your external devices to Cubase via MIDI Clock, do you ever see the indicated tempo on those devices deviate from Cubase’s specified tempo, even briefly? As I noted before, I occasionally see other devices jump up or down one BPM, but only very briefly (less than a second), and it doesn’t seem to elicit any audible issues on any other device but the P12’s delay lines.

Update: I tried the same tests using MIDI-OX.

I used MIDI-OX to send MIDI Clock to the P12 over its USB interface and the delay sync issues persist. When I use MIDI-OX’s default accuracy setting of 5ms, the delay sync issues are extremely prominent at 120BPM. When I dial the accuracy setting back to its minimum value of 1ms, the delay sync issues are significantly less prominent, but they still occur.

Of note: just like when I used Cubase to test, I notice that the EXT BPM value display on the P12 varies most heavily when I send MIDI note data (i.e. play the P12 from a keyboard) while the delays are set to sync to MIDI Clock. The displayed tempo varies mildly on its own, but it varies even more every time I hit a key – it’s a direct correlation and it gets worse when I play more notes and faster notes. This seems like a big red flag to me.

So I previously eliminated my MIDI interface as a factor and now I have eliminated Cubase as a factor. And, again, every other device I have syncs to MIDI clock from my PC without any issue. The delay section of the P12 is the only device I have which fails to sync to MIDI clock consistently with my PC, so I’m having a hard time understanding how this isn’t an issue with the P12.

I sent all of this info to DSI in the hopes that they will take this issue more seriously now.

Good to hear. The usefulness of MIDI-OX cannot be overestimated! Be prepared now to be told that your computer itself, some component thereof, or Windows 7x64 itself is at fault; in other words, get or borrow an old laptop running XP, and repeat the same exercise. Then they really won’t have a leg to stand on.

Update: DSI support wrote back yesterday and now they say they’re able to reproduce the issue themselves, so they’re adding it into their list of issues to examine further. Sure seems like a bug to me.

Thanks again for the MIDI OX suggestion – I’ve had it for years, but never saw that feature. Syncing the P12’s delays to MIDI OX generated clock over the P12’s own USB MIDI interface is the most straightforward test I can think of, and it should be easy to test with other rigs. As I noted before, the addition of note data into the mix really makes the delay sync issue worse which suggest to me that the MIDI clock data stream may be getting interrupted (though I don’t claim to be a deep MIDI expert).