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Re: on octave dividing



Title: Re: on octave dividing
Andy simultaneously explains what I did and probably clearer, but:

Octave pedals.
analog - uses a simple divider circuit, so produces a synth sound unrelated
to the timbre of the input. (although some have an output which tracks the
input in volume)

Not in general. Two types of analog circuits:
- Either the effect sound is taken from a rectangular wave whiches volume is adapted to the input volume, and the ouput timbre is not related to the input timbre (Polysubbass)
- or the phase of the input signal is alternated at each wave end, which is easier since the volume is given by the input signal. The timbre is altered drastically by the phase turn but it still depends on the input signal. (Boss, Yamaha, Mutron...)
A sine wave input turns the following output:                                              
                                                 
     ...         ....                            
    .   .       .    .                           
   .     .     .      .                          
  .       .   .        .                         
 .         . .          .                        
.           .            .           .           .
                          .         . .         .
                           .       .   .       . 
                            .     .     .     .  
                             .   .       .   .  
                              ...         ...    
A different input into a different output accordingly. Depending on at which zero crossing you flip the phase, a sawtooth turns either into a triangle or:
                                                              
.         .                 .         .         
..        ..                ..       ..         
. .       . .               . .     . .         
.  .      .  .              .  .   .  .         
.   .     .   .             .   . .   .         
.    .    .    .     -- >   .    .    .    .    .
.     .   .     .                     .   . .   .
.      .  .      .                    .  .   .  .
.       . .       .                   . .     . .
.        ..        .                  ..       ..
.         .         .                 .         .
You can also flip at the maximum (or minimum) of the wave (Yamaha) which results into other waveforms as you may draw them yourself now :-)


Rectangle results in rectangle

These have a very fast response. They don't do chords. May
have very irregular tracking.

By far the smartest tracking is done by Mutron: there is a kind of a frequency memory, so when the input signal fades and becomes impossible to track, the Mutron Octaver goes on using the same frequency for the said phase alternation.


digital - complex process, so you always get a delay. Signal output attempts
to sound like the input slowed down. Will work with chords, but will be
optimised for either single notes or chords.  Always tracks, but signal may
be broken up.  
right, I forgot to mention the delay in my text.
In the Polysubbass, I fade in slightly delayed to avoid the octavation of the beginn of the attack which is not low anyway. The clean original attack of the string is the most acurate possible. Bass establishes slowly by its nature.
-- 


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