I am not an expert but this sounds a little confused. First of all, a DCO usually means a circuit that creates an "analog" electrical signal. This does not happen in the CZ's. My understanding is that instruments of this type/era (e.g. CZ and Yamaha DX) do as much as possible in the digital domain, and then pass through a DAC and reconstruction filter at the end. There is no place for a DCO in such a design.
The way you create a sine wave in such a system is to have a look-up table of numerical values that allow you to approximate a sine wave as a step function. The value sent to the DAC is determined by a "phase accumulator", a sort of pointer into the lookup table. The rate at which the accumulator increases determines how fast you step through the lookup table, which then determines the period (pitch) of the signal created by the DAC.
If you increase the accumulator at a constant rate then you create a sine wave. If you change the rate of change, however, you start distorting the sine wave that is created by the DAC at the output. This is my high-level understanding of what phase distortion in the CZ's is doing.
2018-09-10 14:46 GMT+02:00 Sean Luke sean@... [CZsynth] <CZsynth@yahoogroups.com>:
I am pretty confused about PD. Can anyone help me here?
1. PD seems to have two different descriptions. One is the description that appears in the Casio series manuals, where a sine wave is being distorted by a bent sawtooth. The other is a figure which comes from the PD patent: you can see the figure here https://en.wikipedia.org/wiki/Phase_distortion_synthesis Note that the sine is being both distorted and then amplitude-modulated. Can anyone tell me which of the two is correct for the CZ series? If it's the example in the manual, a sawtooth is easy, but how does one "bend" other DCO Waves so as to distort a sine? Or does a plain sawtooth get morphed into the DCO wave in question so as to distort the sine?2. I am confused by the sound output being displayed on various websites, such as http://www.kasploosh.com/projects/CZ/11800-spelunking/7-window-unique.html My understanding is that the wave produced by the DCO is used to distort a sine wave, and this distorted sine wave is the final product (ignoring the DCA) sent to line out. Furthermore, the manual suggests that at one end of the DCW modulation we have a pure sine wave and at the other end we have the distorted sine. However these websites suggest that the DCO wave can be viewed directly at line out. What am I seeing here? Is this the DCO wave? Is it the distorted sine wave which for some reason resembles the DCO wave? Etc.Sean