how do you calculate frequency of an lfo?

[ppatchmods]

i'm working on a project and i added the lfo of the ea trem. i'm now going to be replicating the lfo in digital format with a pic. how do i calculate the frequency of the lfo? i also need to calculate the depth into percentage to be able to replicate the parameters? thanks to any help that can be offered!

[Johan]

figure out wich cap gets sharged/dis-sharged and through wich resistor.  T = R x F  time=seconds R=Ohm and F is Fahrads, not mF, not pF, not uF, but F ( thats why the R need to be big if you want low freq. oscillation..)
J

[ppatchmods]

thanks

[PRR]

> T = R x F  time=seconds R=Ohm and F is Farads

The EA Tremolo uses the 3-RC oscillator.



The first R is varied 1K-101K. The third R, 2.2Meg, is Miller-effected to a much lower effective value.

F is not really proportional to any of the R-C products in this plan.

A web-search on "Phase Shift Oscillator" will turn up formulas for equal-R and possibly the tapered-C variant, but this specific type may be hard to find.

> how do i calculate the frequency of the lfo?

Easy answer for most any trem: start with nominal 2Hz. Get it working. Then, since the rate is just software code, dink with numbers in code to give a range similar to the original, or larger to take advantage of the wider range of computed waves compared to 29-cent discrete oscillators.

Depth too may as well be by-ear. Start with some large variation of gain. Oddly the EA only increases gain, minimum 4 max maybe 10. Fiddle the numbers to sound right.

[PRR]

Simulator says:

min R -- 6.3Hz
max R -- 1.67Hz