[sdiy] Triangle wave octave generation (frequency doubling)

mark verbos mverbos at earthlink.net
Wed May 27 21:17:18 CEST 2009


It might be cool to have an integrator for each saw and have the  
comparator on the highest one. Send the reset pulse through dividers  
(4013 or whatever) and then use that to the reset transistor on the  
lower integrators. At least the saws wouldn't be glitchy.

Mark




On May 27, 2009, at 2:59 PM, JH. wrote:

>> I achieved something like this with a sawtooth in my modified Jen  
>> SX1000.
>> In my case I watch the rising sawtooth with a comparator, and when it
>> reaches a set level I force a reset. There's also a matching  
>> variable gain
>> amplifier to compensate for the reduction in amplitude.
>
> With *saw* waves, it may be easier to start with the highest octave,  
> and
> derive the lower octaves from that.
> It's the old Korg trick: Create highest saw and pulse, then divide  
> down the
> pulse with flipflops, build a staircase wave from the divided  
> pulses, and
> then fill the steps of the staircase with the saw from the highest  
> octave.
> That way, you get saw waves for every octave just with flipflops and
> weighted summing.
>
> I have used it in my JH-720 VCOs, which are more or less copied from  
> the
> Korg 700 and 800DV:
>
> http://www.jhaible.de/jh_720_vco_core.gif
>
> JH.
>
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