[sdiy] Techniques for Multiplying MIDI Clock frequency?
Adam Inglis (synthDIY)
synthdiy at adambaby.com
Sat Dec 18 22:32:11 CET 2021
Avoid DAW generated midi clock like the plague!
Innerclock have addressed this problem.
They use an audio pulse generated by the DAW to produce jitter-free midi clock in hardware, with optional pulse outs of between 4 - 96ppqn.
btw, that KPR problem is not unique: the TR-909 has a similar bug in V1 of it’s firmware, where it would “lose” midi clocks when being slaved. I always slave to DIN sync to get around this.
> On Sat, Dec 18, 2021 at 3:00 PM Benjamin Tremblay <btremblay at mac.com <mailto:btremblay at mac.com>> wrote:
> If I’m waiting around doing nothing until I count 12 pulses, all that matters is I construct a square wave 12 pulses long.
> Benjamin Tremblay
>> On Dec 18, 2021, at 3:56 PM, Benjamin Tremblay <btremblay at me.com <mailto:btremblay at me.com>> wrote:
>> I’m assuming all it does is divide by 12 to get a 16th note.
>> Benjamin Tremblay
>>> On Dec 18, 2021, at 3:53 PM, Pete Hartman <pete.hartman at gmail.com <mailto:pete.hartman at gmail.com>> wrote:
>>> On Sat, Dec 18, 2021 at 2:15 PM Benjamin Tremblay via Synth-diy <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
>>> 2) I wish I understood the theory of clock multipliers. I have seen code that measures the period between clock pulses and dead reckons the double-time pulse as an average of the recent periods. But why? Why can’t I just fire another extra HIGH-LOW pulse whenever I get a MIDI clock event? Why does timing of the extra ticks matter? I’m assuming 48 PPQ divides the clock down to individual sequencer steps on the KPR-77. As long as the divided clock is coming in on the beat, what does it matter if some of the synthetic pulses are a little off? (They’re just shadows of the main tempo clock). It’s not like the KPR-77 is inferring something or trying to calculate BPM from the external clock… So… Anyway I just wish I knew what I was aiming for, and then maybe I could hit the target.
>>> One suspects that most people are trying to write a general purpose converter. E.g. you could run those 48ppq out to some other module, like an analog sequencer, and it would keep time. I'm not familiar with the KPR-77, but I'm also slightly puzzled by the idea that some piece of gear would require 48PPQN but not care about the timing of half of the pulses.
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