LFO rates and waveform shapes
2001-07-10 by Jerry Aiyathurai
An1xers: I must be having too much time on my hands. Yesterday I started recording An1X oscillator tones and looking at waveforms. I also started timing tests on LFO 1. I came up with the following table which is pretty good up to three significant digits, I reckon. Note that since the LFO's don't lock to anything, it would be a waste of time using this table for synchronizing BPM. You would be best served using this as a reference for programming vibrato, tremolo, chiff, growl and other kinds of modulation things. LFO 1 Setting Rate (hz) 1 0.042 5 0.210 10 0.421 20 0.841 30 1.26 40 1.72 50 2.31 60 2.90 70 4.04 80 4.96 90 5.89 100 6.77 110 7.87 120 9.82 130 10.1 140 12.7 150 15.2 160 18.3 170 22.4 180 27.6 190 34.3 200 43.4 210 54.9 220 71.2 230 87.8 240 111 250 141 256 162 The waveforms were very interesting. I found a couple of surprises: - All the waveforms were far more rounded than I expected even at an edge of 127 - The pulse wave (at edge of 127) was more lopsided than I expected. It had a sloping top line, looking more like a truncated saw, than a square. (I guess they wanted to give us the possibility of more overtones, should we need them.) I didn't play with pulse width, though that is my next test. - The saw, pulse, saw2 and mix waveforms, collapse to a pure sine wave when edge goes to zero. The exception is the pulse wave under oscillator sync, which collapses to sine only when edge is zero AND sync pitch is minus 12. (I wonder if the slave is tuned up by an octave, or something? why?) - The internal (1,2,3) waveforms would not collapse to sine under any circumstances. They appear (visually) to be stacked saw waves tuned to the harmonic series. I am not sure specifically which overtones they are tuned to, but I know it is not a simple octave relationship, as I could not collapse them to sine by playing with the sync tuning and edge. Each individual element would get more sine like, but not the combined waveform. My opinion: I suspect (but I am not sure) that these are saw waves at an octave above and 1.5 octaves above. The difference between the waveforms (int1, int2, int3) lies in the relative volumes of the overtone waves. I may be off base with these observations. I am hoping someone from the list may have an inside scoop (Gary?), or has done more extensive tests. Anyway, I hope this info helps someone. Cheers, Jerry