[sdiy] 24 --> 48 PPQ double clock pulse

[Theo]

Assuming the 24ppq pulse is 50% dutycycle generating a short pulse on very hi/low and low /hi transition as you propose seems a usable method.

The bad news; most probably your 24ppq clock pulse is not 50% dutycycle :(
Therefore IMO your best option might be to use a PLL circuit like a 4046.
The data sheet will show you the circuit because this is a typical application for a 4046 :)
Down side of this solution is that the PLL might need some time to lock to a (sudden) tempo change.

However when your 24ppq clock is indeed symmetrical, generating pulses on every transition is indeed a option.
The advantage would be that is doesn't have tracking problems when the tempo changes.

You can do this quite easy with 3 Schmitt trigger gates like those in the 4093.
The data sheet for the CD4093 on the Fairchild-semiconductor website shows how to make a negative triggered "gated one shot".
You need two of these, one you feed with the 24ppq pulse the other with the inverse of the 24ppq pulse.
The output of the "one shot" circuits can be added together with 2 diodes and a 33k resistor to ground where the diodes meet.
Basically you now have your 48ppq pulse, but it might be a good idea to buffer this signal.
One way to do this is to send it though the left over 4th gate in the 4093. 
The 4093 gate inverts the signal therefore you need to add a second inverting circuit as output buffer.
Otherwise your 48ppq clock would run slightly "late".

HTH
Theo



  ----- Original Message ----- 
  From: E.B.S. 
  To: synth-diy at dropmix.xs4all.nl 
  Sent: Monday, October 28, 2002 4:40 PM
  Subject: [sdiy] 24 --> 48 PPQ double clock pulse


  Hi everyone,
  I just subscribed again after a few years. Is the list still active? This list helped me great in the past and now i have a question.
   
  Last week a bought a Linndrum and already like it alot. To sync it to other devices there is a clock in and out. I allready found out it runs on 48 PPQ (pulses per quarter measure). My problem is that the rest of my drummachines run on 24 PPQ (roland boxes) so i would like to double the pulse rate.
   
  Is there a simple circuit that can do this? 
  I thought of something that outputs a pulse on the start and end of the 24PPQ pulse but i don't know how to implement this. Are there any other (better) alternatives? 
   
  Any help would be much appreciated.
   
  Thanks in advance.
  Greetings,
  Eric (Amsterdam)
   
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