Tremulus lune LFO cap

[kristopher612]

hi there everyone.  I built up a tremulus lune this afternoon, using the PCB layout from 4ms, and forgot to put in the .01 cap in the LFO before i tested it, and the LFO still worked.  can anyone help me understand why this would happen?  i put it in once i noticed that it was missing, but upon testing it a second time, i didn't notice any difference in the LFO's operation or range.  thanks for any insight that can be given on the subject.

[frequencycentral]

That cap is not the timing cap, although it does have a small effect on the timing. The (100uF?) electrolytic is the timing cap. The 0.01uF cap seems to serve to round off the very peak and trough of the waveform, and to prevent ticking. Maybe not noticeable in the Lune because the control and audio are isolated from each other by the LED/LDR, but omit that cap in a similar LFO in a different pedal and you will certainly get audible ticking. I'm surprised you didn't experience any ticking bleeding into the audio path, but then again there are so many ways to set the Lune that you may not have discovered the settings which resulted in bleed before you added the 0.01uF. But yes, that LFO will certainly work without that cap, just not perfectly.

[kristopher612]

well i should say that i didn't test the audio.  i fired it up in a hurry just to make sure the LFO was working and test voltages.  i did put the cap in just because it is a part of the circuit and wanted it to be correct.  thanks for the explanation of what the cap is doing in the circuit.