combined waveforms

The SID chip provides 4 elementary waveform generators (triangle, sawtooth, pulse and noise) that can be activated to generate the output of any of the 3 voices. As a special "feature" it is also possible to activate more than one of these generators at the same time - which leads to rather strange combined waveforms.

Here some examples:

  • Probably the most popular combination is "triangle&pulse" and one of the more well known examples is Kentilla which starts with 2 voices using the respective combination.
  • A similar combination is "saw&pulse" and though it is used less frequently an example can be seen in action in Dawn where it is used on voice 2 right from the start.
  • Also less popular seems to be "triangle&saw" of which an example can be easily observed in Adc where it is used on voice 1 right from the start.
  • The combination of "triangle&saw&pulse" is more difficult to observe in the wild. An example can be found in Zebra_Jam where it is used on voice 3 about 20 secs into the song (it sounds like some cheap wind instrument).
  • The most exotic case among combined waveforms is finally any combination that also uses "noise": Here the SID chip uses a feedback mechanism that causes the other waveforms to quickly clear the the "noise" generator's state - resulting in a disfunctional "noise" waveform (which has to be manually reset before its regular functionality is restored). Some songs use this with the intention to create a "metalic" drum sound and an example of these is Skaermtrolden_Hugo. A creative case is Bojojoing where the "noise" decay process is then interrupted to result in a periodic "noise" waveform on voice 3.


output of the three regular SID voices (including effect of the filter):


 

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