Logarithmic Frequency Sweep

[SBMastering]

Hi,

Some time ago I did a linear frequency sweep in Synthmaker. I'm attaching the FSM file.

I now have a necessity for a logarithmic frequency sweep instead. Does anyone have any ideas how this might be accomplished?

[trogluddite]

A simple power function should get you a nice log sweep, for example...
freq = base_freq * (2 ^ time)
...would rise by one octave from the base_freq each time 'time'; increases by one. In Ruby, the power operator is '**' not '^', so it would be... freq = base_freq * (2 ** time)

[SBMastering]

I couldn't get the power operator to work in the regular code window with "^". It just turns everything into black text. I have looked all over. I'd hope to avoid doing it in Ruby because I haven't been working in Ruby much yet and this just needs this one little tweak!

I'm posting a screenshot of the sweep. Also, please check out my uploaded example on my previous post.



BTW, Trog, I am going to PM you about something unrelated.

[Tronic]

use pow(e,n) for ^

[SBMastering]

Ok, I got it working with pow and increasing logarithmically. Now I'm working on trying to figure out how to get it to decrease logarithmically after it reaches it's highest point.

[tester]

?

What makes the "movement" logarithmic - is the signal scaling itself, not direction you go. It works like this. If you rescale your values into (0-1) range, and apply lin to log transformation, then what will change is the curve between 0 and 1, but the range remains the same (then you may rescale it back into whatever you wish). By curve I mean corresponding y values to x values. In linear case y=x (or y=nx, depending on initial scaling). In other cases - all depends on what you used.