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clock drifts when using BB as master.

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  • clock drifts when using BB as master.


    Master clock: Blackbox
    Midi out -> keystep pro

    From keystep pro to other gear.

    The keystep pro shows the bpm realtime, so any adjustments made can be seen on the screen.
    When I use the BB as master clock and hit the play button. The keystep starts like it should, but the bpm drifts between 120 and 121.

    Both devices are up to date to latest versions. I tried midi out with the midi-trs and midi out over usb.
    Tried setting clock to 24ppq (keysteps default is 24) no difference.
    I am powering the keystep with 12v adapter.

    I tried to run nothing on the BB (no clips and such) just hit play only. Even then the bpm drifts.

    Somebody has an idea why this happens?
    Thanks in advance

  • #2
    I don't know exactly what the technical reason for this is, but in my experience this happens frequently across a range of MIDI synched instruments, including Ableton Live. It has never been an actual problem with reliable/measurable sync, just how it fluctuates in the display in my experience. You could try recording and measuring the timing if you're unsure.


    • #3
      This is normal behaviour for any counter-based tempo meter.

      A BPM meter like this works by measuring the time between incoming clock ticks and factoring that value into BPM.
      A MIDI clock sends 24 Pulses Per Quarter (PPQ), so we are in the realm where a measurement that is off by a few hundred microseconds will already make a difference on your BPM meter.
      Additionally, the time measured between ticks can fluctuate, even at a steady tempo, due to skewing of real time vs. logical time.

      The good news is that this usually averages out nicely over the course of a few pulses.
      Last edited by Michal Ho; 06-09-2021, 01:33 AM.


      • #4
        Oh by the way, you could try using the Analog Clock Out on the BB instead of MIDI to drive the KS pro.

        That clock is trig-driven, meaning each pulse actually moves the sequencer forward on the KS, instead of just telling the KS clock how fast it should be.
        Some people swear by analog clocking, saying it feels much tighter.
        Last edited by Michal Ho; 06-09-2021, 04:31 AM.


        • #5
          Great explanation. Thanks to both!
          I was suspecting that this was maybe only a small thing in the bpm meter. Because I don't experience a drift in time by listening. Everything sounds ok to me. Maybe ill check with a recording to see, but I think it's not a problem seeing your explanation.

          Trying out the analog clock signal... I kinda forgot that was also an option haha. Great suggestion, I'm going to try it out