[sdiy] "Living VCOs" PCB in 2009 ?

[Dave Manley]

JH. wrote:
>> Now if somebody is designing a new unstable VCO,
>>     
> Just to clarify: I have nowhere described my JH-5 VCOs as "unstable".
> In fact, if you read the short text at the link I've posted, I'm talking 
> about quite the opposite.
>
> JH. (puzzled)
>   
The problem with this discussion is the use of the subjective term 
"living".  The term conveys no technical information, and has caused the 
discussion to "go off in the weeds" in a number of different ways.  I 
don't know if you are intentionally or inadvertently not providing this 
key definition in a more straightforward manner.   The term obviously 
has some specific meaning to you, which is unknown to the list, mainly 
because I don't think list members read the text you referenced in your 
original post.  From your JH5 page we read:

"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."

See: http://jhaible.heim.at/jh5/jh5.html

 From this one *might* conclude that linear, as opposed to expo, 
detuning is the key to the 'living VCO'.

I recalled an old submission you made regarding a linear detuning 
modification to the Oberheim SEM.  Digging in my files I found a copy 
from July 10, 1997 which is archived here:
http://web.archive.org/web/20051220015016/http://home.swbell.net/roy_tate/info/lindetun.html

The key thought at the end of that post: "...I just wanted to show that 
there might be some *tendency*, some *trend* from very rich sounding 
synths at one end to very precice sounding instruments on the other end. 
And that the reason for this is not black magic, but of some physical 
nature. And, that this may have something to do with a linear term in 
VCO detuning."

Many expo VCO implementations include a linear modulation CV port, and 
so on to the next question: does the 'living' VCO do more than provide a 
knob to adjust the linear detune amount?

-Dave