Schematics / Juergen Haibles Living VCO
Juergen Haible's Living VCO ,the page dedicated to this module is here : http://www.jhaible.de/living_vcos/jh_living_vcos.html ,thread on the forum : http://electro-music.com/forum/viewtopic.php?t=30749 This is how Juergen Haible describes this VCO design :
My goal was to build a set of VCOs that have the untamed bass range power of early EMS and Moog VCOs, but which are tracking a keyboard voltage over 5 or more octaves nevertheless. I found that "untamed" Beating in the bass range and controlled beating in higher octaves is not possible with standard exponential 1V/Oct oscillators. A good part of that special sound of early Moog and EMS oscillators is not because of any "randomness", "unstability", "instability" or "noisyness", as so often is said. A good deal of their behavior is because of that, but it is not the whole story. There are also some very deterministic factors in these old circuits which have been unpleasant side effects for the designers back then, but which are worth a closer analysis when we're designing a musical VCO today. This is implemented in form of three "linear detune" potentiometers on the JH-5A VCOs.
Discrete (no opamp), noisy servo in expo converters (VCS3 feature) Emulation the low frequency behaviour of linear (Hz/V) VCOs and of leakage (EMS VCOs) Capable of very pleasant beat rates between the VCOs over the entire keyboard range Allows rich and powerful animated bass sound, and smooth "phasing" slow-beating sound in higher octaves Discrete (no opamp) pulse width modulators (capable of smooth audio rate PWM) Limited PW range allows PWM overmodualtion (CS-80 feature) Low level (Moog) or high level (MOTM) outputs VCO driver with two CV inputs, LFO oscillator with limited speed range and voltage controlled amount Accepts potentiometer (passive modulation wheel etc.) or CV for vibrato control Exponential (RC-Shaped) Portamento Either one shared, or 3 individual potentiometers for Initial Pulse Width
visit his page for detailed analysis : http://www.jhaible.de/living_vcos/jh_living_vcos.html