Doepfer

I should read your books more carefully :-)

Dieter


> -----Ursprungliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von Florian Anwander
> Gesendet: Freitag, 1. August 2008 11:17
> An: Doepfer_a100@yahoogroups.com
> Betreff: Re: AW: AW: [Doepfer_a100] discontinuation of all modules with
> CEM3320, CEM3340 and CEM3381/PA381
> 
> 
> Hi
> 
> > Is it?  What's the difference between the effect of having different  
> > cores?
> The theoretically resulting waveform of FM is only "real" for the core 
> wave form. All other waveforms will be that, what the waveform converter 
> produces from the fm'ed core-waveform.
> 
> 
> I uploaded two graphic files to the files section:
> http://launch.groups.yahoo.com/group/Doepfer_a100/files/analog-fm/
> These are excerpts from my book.
> 
> I some months ago wrote the following text in private mail to Bakis, 
> which explains the images:
> -----------------------snip------------------
> 
> The most relevant thing is: FM with analogue VCOs has nothing to do with 
> the theoretical FM, because everything depends on the working principle 
> of the core oscillator (saw or triangle), and what the waveformconvertes 
> make out of the fm'ed core wave form.
> 
> I'll attach two excerpts from my book:
> analogue_fm.png explains what really happens in a saw based VCO. Left is 
> an log FM, right is the linear FM:
> 
> * the first row (rectangle) is the modulator with an amount of +1V to -1V
> 
> * the second row (400Hz saw) is the carrier
> 
> * the third row shows the two saws which would be created by a CV of +1V 
> and -1V. In log FM this will be 1V up/down => 1 Octave up/down, => 
> 800Hz/200Hz. In lin FM this will be 1V a certain frequency up/down, => 
> lets say 200 HZ => 600Hz/200Hz. The higher result(800Hz or 600Hz) is 
> light grey; the lower result (200Hz) is dark grey. The two frequencies 
> look like two ramps with different steepness.
> 
> 
> * Now the fourth line shows what really happens in the VCO: There is a 
> thin horizontal line, which is the threshold at which the Capacitor in 
> the core-oscillator is unloaded.
> The rectangle switches between the two steepnesses. With the bigger 
> steepness of the 800Hz at the log FM the resulting wave form will reach 
> the threshold faster than with the "600Hz-steepness". As you can see the 
>   threshold will be reached at the same time as with the original 
> carrier signal.
> 
> Thats the one graphic.
> 
> 
> The second graphic shows, the same FM, but this time not the core saw 
> oscillator, but the output of different wave forms from the waveform 
> converter. The Modulator still is the known rectangle.
> Line a shows what we would expect for a triangle carrier.
> Line b shows what we would expect for a rectangle carrier.
> Line c shows what we really will get at the triangle output.
> Line d shows what we really will get at the rectangle output.
> 
> The latter two show, what the waveform converter will create from the 
> originally FM'ed saw from the core-oscillator. Here you can see that 
> this has nothing to do with real FM
> -----------------------snip------------------
> 
> ------------------------------------