# [sdiy] Techniques for Multiplying MIDI Clock frequency?

Pete Hartman pete.hartman at gmail.com
Sat Dec 18 22:37:14 CET 2021

```Right, if you have a factor of 2 in there, that may hide the problem.  But
if you want to simply divide into 32nd note triplets, you're screwed :-D

Pete

On Sat, Dec 18, 2021 at 3:35 PM Benjamin Tremblay <btremblay at mac.com> wrote:

> I was seeing it like a square wave based on 48ppq divided by 12. In that
> case, it doesn’t matter what the duty cycle of the wave is, what matters is
> the the frequency.
> The counter goes ONE 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, TWO, 2, 3, 4, 5,
> 6, 7, 8, 9, 10, 11, 12… And as long at that first pulse (which is not
> synthetic) lands on the right time, it works perfectly.
> In theory the other 11 pulses could be all bunched together and it would
> not matter.
>
> On Dec 18, 2021, at 4:23 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
>
> 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>
> 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> 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> wrote:
>>
>> ﻿
>>
>>
>> On Sat, Dec 18, 2021 at 2:15 PM Benjamin Tremblay via Synth-diy <
>> 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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