[sdiy] Techniques for Multiplying MIDI Clock frequency?

[Tom Wiltshire]

I'm with Pete. Arguing that "we're doing timing, but it doesn't matter where the pulses fall" seems like a one-way ticket to failure.

Unless "drunk jazz drummer" is the effect you're after? ;)

> On 18 Dec 2021, at 21:10, Pete Hartman via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> Right but where the divisions are going to fall when you're doing an odd divisor that includes a factor of 3 is going to shift around if the pulses being divided aren't evenly spaced.
> 
> I tried to make an ASCII representation to verify this expectation:
> 
> |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |      Original pulse train
> | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |    evenly divided
> |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |    divide by 3
> ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||  ||     unevenly divided
> |    |      |    |      |    |      |    |      |    |      |    |      |    |      |    |      |    |      |    |      |    |     divide by 3
> |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |     |    the even div/3 for comparison
> 
> Hopefully everyone's email clients can cope with the monospace required to make this obvious.
> 
> 
> 
> 
> 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.
>>> 
>>> Pete 
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