comment posted on the main VOS Synth page:
“I still dont understand the switch s2. are you sure that the schematic is correct?
in the video, you move up and down the switch s2 and in these 2 cases the lfo signal generated by the 555 is sent to the 556, I say this because in the 2 cases you move the pots of the lfo (r8, r7, r6) and they modify the sound.
according with the schematic and using a 2-pin spst switch, the lfo signal should only pass to the 556 when the s2 is up, and when the s2 is down, the signal not pass to the 556
Is this what i say is true
help me whit the s2, please ! ! !
can i connect the synth out to my pc, to add effects (via soft) and to record it, with no risk to cause damages on the sound card?”

Response:

The circuit was developed by a bit of trial and error and circuit bending other stuff… although S2 disconnects the LFO from the rest of the circuit when it is open (down), the power drawn by the 555 still affects the downstream oscillators. We kinda like this… If you don’t want this to happen, put a small cap (.01 to .1) uF across the power and ground of the 555, and this shouldn’t happen, but the overall sound loses some character. We’ve been making fixes and revisions to the circuit since the first video came out, so there may be some slight differences in how it sounds, but for the most part, it’s the same.

To record on your computer, I’d start off with the volume all the way down, and then slowly bring it up to a suitable level. The VOS is capable of supplying more voltage than a computer’s audio port is typically used to at full volume, but you should be safe at lower volumes. We’ve recorded into lots of equipment (including a computer) without problems.