Posted: Tue Feb 07, 2017 4:53 pm Post subject:
Anti-aliased quad sawtooth subharmonic generator Subject description: generates 4 anti-aliased subharmonic sawtooths from one master sawtooth oscillator
This building block generates four subharmonic sawtooth oscillators from a master sawtooth by a non-trivial (ie. anti-aliased) method. The divisor for each subharmonic can be individually set (elegantly via clock divider modules) as can its level be adjusted.
The patch works by isolating the BLEP residual from the master sawtooth oscillator and multiplexing it into four sub-divided BLIT streams which then are summed and integrated. (The integrator is leaky as not to accumulate DC.)
I used an OscA as a master, since it (as well as the OscB) has way better anti-aliasing than the other oscillator modules.
To re-iterate the obvious, this circuit will only work properly with a sawtooth wave.
cheers,
t
EDIT: Programming tip: set the divisors of the four subharmonic generators to 2,4,8 and 16 for total suboscillator overkill.
QuadSubharSaw_TK.pch2
Description:
generates 4 anti-aliased subharmonic sawtooths from one master sawtooth oscillator
Posted: Tue Feb 07, 2017 6:14 pm Post subject:
Re: Anti-aliased quad sawtooth subharmonic generator Subject description: generates 4 anti-aliased subharmonic sawtooths from one master sawtooth oscillator
Blue Hell wrote:
Tim Kleinert wrote:
[...]works by isolating the BLEP residual from the master sawtooth oscillator[...]
Tim, you are nuts
Very interesting idea
It ain't rocket science. I just take the derivative of the sawtooth output (with my neato 2-module differentiator) which yields the differentiated BLEP pulse plus a DC constant from the sawtooth incremental. This is also separately captured once via S/H at zero-crossing (remember that the G2 sawtooths are actually ramps) and subtracted from the continuous differential -yielding the pure BLIT, albeit in differntiated form, which is irrelevant since it gets re-integrated again anyway afterwards.
Of course integrated BLITs aren't as clean and accurate as BLEP sawtooths, but, hey, it gets the job done.
EDIT: After rereading some of the literature, I noticed that one of my above statements is inaccurate. The BLEP is, as its acronym states, a BandLimited stEP function, which results from integrating the BLIT. So, by differentiating the sawtooth waveform and subtracting the resulting DC component coming from the ramp increment, the BLIT is properly retrieved. It isn't 100% pure though, since my hack ignores the phase wrap-around, resulting in a small amount of DC jitter -but it's usable. Last edited by Tim Kleinert on Mon Feb 13, 2017 3:07 pm; edited 1 time in total
Very usefull with my pythagorean tuning patch. I love to use shaper and other stuff on harmonics (without phase). This patch give me very nice results after 10 minutes! I need to integrate this building block in my patches ASAP!
Quote:
It ain't rocket science.
How many time before the : "special and limited Tim Kleinert expension board rocket science" for G2 ???
EDIT: Programming tip: set the divisors of the four subharmonic generators to 2,4,8 and 16 for total suboscillator overkill.
Possible to edit the patch a bit to retrig all subharmonics at the begining of the cycle for each one. Or adjust where the cycle start for each of them. Important to have all of them perfect in tune when we adjust the 'divider' parameter on SUBHAR modules in the patch in real time. To sync them just use the Rst input on SUBHAR modules and the Sync on the main oscilator module with your source (Kb / sequencer / ...).
Ha! I love this tuning ... when the level indicator from the output module flash very fast and go to the red zone without go to yellow zone before. When you have no choice to add limiter or be carefull with clipping because of the tuning
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