Need Explaination on Tim's Quasi Synths

[jmusser]

These circuits sound interesting, but I'm not sure exactly what's going on with them. It say's one of the circuits oscillates with the resonance maxed, and with one set at minimum. I'm lost on this whole concept. So far the closest I've come to the Synth sound, would be the Crash Sync, and I'm guessing your guitar tone changes, because going to the different frets changes the RC time constant of the oscillator, just like it would if you were playing keyboard keys, but I don't know. I'm going way back into the cob webs of mid 70s electronics class to even remember that much!

[jmusser]

In case I was too vague, these are found in Tim Escobedo's Circuit Snippets as Q & D VCFs. I don't even know what VCFs stand for honestly. I would guess "F" is for "Follower" ?

[petemoore]

Voltage controlled filter
 the sweep of the wah or filter sound is controlled by input voltage...say when you hit a note, the attack sound is producing a higher output voltage, than say when you stop playing...also called 'auto wah' the sweep is controlled by playing dynamics [loud to soft] changing voltage output from say guitar or other source.

[jmusser]

I guess the reason I thought this was a different animal, is because I'd always heard of auto-wah referred to as an envelope filter, plus, I'd never associated an auto-wah with a "synth sound". Tim's Phungnosis for example is very attack sensitive like you're talking about, but it's quacky. Would this end up giving you a sythy type sound like an octave down pedal does, only at standard reference signal, or would it just make the standard reference signal buzzy only when struck hard/decay from buzzing after being struck hard? It's just confusing as to what the outcome is. Of course, I'm still confused as to why a rubber band snaps back to it's original shape :?

[Tim Escobedo]

Filters of any kind generally don't give octave down type synth effects.

In the synth world, VCF (Voltage Controlled Filter) is usually implemented as a lowpass filter, tuned by a control voltage (CV) and/or manually by knob. They also usually have a resonance control which kind of synthesizes a overtone. The most dramatic effects are when the filter is swept. In the synth world, the filter is usually swept in a manner dictated by a envelope generator, not a envelope follower. This is because in the completely electronic synth realm, the sound generators (oscillators) have no inherent envelope to follow. The envelope generator allows the user to create the envelope.

In contrast, a plucked guitar string can be thought of as a oscillator, with a inherently distinctive envelope.

[jmusser]

Ahh Haa! I see said the blind man. Thanks Tim! BTW, I left the jumper wire off that goes from the output cap of the LM386 (pin5) to the Reset pin on the timer (pin 4) on the Ugly Face. So once that little guys is installed i'll be in for some serious ugly