[LAU] blvco LADSPA plugin

Fons Adriaensen fons at linuxaudio.org
Sun Mar 11 22:39:40 UTC 2012


On Sun, Mar 11, 2012 at 09:43:56PM +0100, Julien Claassen wrote:


>   I was especially experimenting with the unique ID 1954, REC-vco plugin. 
> When I didn't get the expected result with the sync audio input port, I 
> hunted for the readme and tried to check, if I perhaps thought it was for 
> a different purpose and then I saw, that at the time it was thought to be 
> experimental.
>   So: is the sync port for a typical sync'ed osciallator sound? I tried  
> different things with it and either got no result or harsh sounding 
> results, that sounded more like some sort of ringmod or FM, i.e. in this 
> case destructive. :-)

First thing to note is that these plugins were designed for use in AMS.
That means the the first 6 ports:

  "Output",
  "Frequency",
  "Exp FM",
  "Lin FM", 
  "Mod",
  "Sync",

are audio rate and will show up in AMS as 'control voltage' inputs.
Audio rate here doesn't mean all samples are used and control is
at full audio rate. The inputs are all subsampled.

The others are real control rate:

  "Octave",
  "Tune",
  "Exp FM gain",
  "Lin FM gain",
  "Waveform",
  "Form mod",
  "LP filter"

and will show up as sliders in the plugin's module dialog.

The sync feature is not what you would find on most analog
synths or emulations. It is a 'soft sync' or in other words
a PLL, not a 'hard sync' that would force the oscillator to
a particular point in its cycle. Its intented use is to make
sure that two or more VCOs stay exactly in tune rather than
producing slow beats. If they are tuned closely enough so 
that some harmonic of the first is close to an harmonic of
the second, the synced one will 'snap' to the exact frequency
to make these harmonics equal.

>   Another thing I'm not too sure about the the waveform control input. I  
> changed its value from -1 to 1 in a straight line and no effect.
>   But thanks for these osciallators. They now not only look like 
> interesting and helpful gear, they are!

If you use the "Mod" input to modulate the waveform you need to
set "Form mod" to some nonzero value (it acts as a gain factor
on "Mod").

These plugins are now quite old. I've been working on improved
version (which will have 'hard sync' instead), but they are
unfinished ATM.

Ciao,

-- 
FA

Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.



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