[sdiy] "Living VCOs" PCB in 2009 ?

[JH.]

Hi Dave, you summed it up nicely.

> The problem with this discussion is the use of the subjective term
> "living".  The term conveys no technical information,

I was actually proud I found a short project name that describes what it 
means to me. :)
I had no idea someone could be offended, concluding other VCOs were "dead".
(I don't say other chorus devices cannot be subtle, when I called my Dim D 
clone "Subtle Chorus".
Or that you cannot make Krautrock-style music with other Schulte Phaser 
Clones.
It'd be so ridiculous if I'd imply anything like that, and it's also fairly 
ridiculous for others to conclude something like that, IMO.)

You're right about Linear Detuning. It's one of the key ingredients.
But it doesn't have anything to do with the Linear FM you can find on many 
VCOs. Entirely different thing, as far as I can tell.

JH.

----- Original Message ----- 
From: "Dave Manley" <dlmanley at sonic.net>
To: "JH." <jhaible at debitel.net>
Cc: "Ken Elhardt" <ken.elhardt at gmail.com>; <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, December 10, 2008 11:19 AM
Subject: Re: [sdiy] "Living VCOs" PCB in 2009 ?


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