[sdiy] Divide down question

[Tom Wiltshire]

The sub-octave on the Roland SH101 does the same thing, but uses a  
simple diode-OR to get a 75% pulse wave and avoid needing the AND  
gates. Same trick the other way up, so to speak.

T.

On 25 Aug 2009, at 14:48, David Moylan wrote:

> This was done in the Paia Strings n' Things.  Schematics are  
> floating around on the net.
>
> Dave
>
> Tom Wiltshire wrote:
>> One thing that you can do to get pulse waves is to start with a  
>> standard square-wave divide-down scheme, but then run pairs of  
>> square waves at octaves into AND gates. If you feed a square at  
>> frequency f and one at 2f into an AND, you get a 25% pulse wave  
>> out the far end. You could use 4f and have 12.5% if you prefer.  
>> Given that you've already got all the octaves you need, this seems  
>> like the easiest way to get divided-down/up pulse waves.
>> T.
>> On 25 Aug 2009, at 09:55, Scott Nordlund wrote:
>>>
>>> It could be done with sawtooth waves too:  use a comparator to  
>>> make a square wave, invert it, amplify the sawtooth by a factor  
>>> of two, and mix the two.  Of course the comparator's threshold  
>>> has to be adjusted properly, or there will be asymmetric pulses  
>>> and sub-harmonics sneaking in...
>>>
>