MOTM

Ok, reading that post about the synthesizers.com octave switches led 
me to thinking on the 2 hour ride from my home in CT to my playground 
in upstate NY.  Ok, here's section one.  (Excuse my spelling)

The "Oscillator Helper"
Synthesizers.com has one, but your VCOs don't need one in the sense 
that theirs is a "Helper."  I was thinking more of a voltage 
adjustment unit that's precice.  Assuming (and this is a big 
assumption) that your VCOs always respond to one volt by changing one 
octave no matter where you are on the scale, a voltage bias unit 
would be quite cool.  I was thinking a unit with two "selector" 
knobs, one that's maybe -12 to +12 1/2 steps, and another that's -6 
to +2 octaves.  (Possibly change it to -6 +6 half steps and -6 to +6 
in half-octaves.  I like the other idea better.)  Why would you want 
selectors like this when you could just grab the coarse knob?  When 
you grab the coarse knob and set your VCO up an octave, you've got to 
tune it again.  Sure, it's not too terribly annoying to re-tune the 
osc. but I think it'd be nice to have access to a quick tuning 
selector.  Granted it's biased towards western scales, but so is 
Volt/Octave.  Anyway...  Another feature would be some sort of 
detune...  reason for this?  shown below...

Too Much Stability?
   I've always thought that the quirkiness of analog synths is part 
of the charm.  I'm almost wondering if there's a tangible difference 
between a nearly perfect VCO and a Digitally Controlled one.  Don't 
confused DCO with DO, though.  My understanding (which might be 
flawed) is that a DCO is an analog oscillator tightly paired with a 
digital circuit that maintains the tuning of the oscillator, while a 
DO is just a digital oscillator, using a DAC I guess.  So back to the 
point, if these VCOs are so stable, what's the difference between 
using them and using a DCO?  Wouldn't it be more practical (although 
some purists would be mad) to have a modular, voltage controlled 
DCO?  Ahh, there's a problem there, I see, since you couldn't have 
the unit really respond to a CV signal for tuning, since the digital 
circuit wouldn't know where to tune it to be "correct"... although 
you could do it anyway (on the assumption that the Midi->CV converter 
or your CV keyboard is 100% accurate), or just have a MIDI equipped 
DCO.

Anyway, I'm not saying that I prefer DCOs at all.  I just wonder if 
having a super-stable VCO takes a bit of the warmth out of a modular 
synth?  Again, I'm not sure just HOW stable these VCOs are, if they 
vary by +/- .5 hz then that's one thing, but if it's +/- .001 hz it's 
another.  So, if these VCOs are uber-stable, why not add a goofiness 
factor to the unit I made above, controllable with a pot, CV control 
being probably quite useless.

Regardless of the goofiness factor, I think an accurate, selector-
type module to reside next to the VCO would be neat.  It could even 
have two identical sections.  All it would need (for a basic unit) 
would be 4 selectors, 2 CV ins and 2 CV outs.

Ok, that's all for now, feel free to shoot my suggesions to heck, or 
embrace them as if heaven-sent.  Whee.  Time to go to sleep!

-Overand (Sucrose)  www.overand.com

----- Original Message -----

From: <sucrosemusic@...>
 I was thinking a unit with two "selector"
knobs, one that's maybe -12 to +12 1/2 steps,
and another that's -6 to +2 octaves.

--LH--
Been there, done that...
http://www.wiseguysynth.com/larry/jlh-822/822.htm

From: <sucrosemusic@...>
Too Much Stability?
Anyway, I'm not saying that I prefer DCOs at all.
I just wonder if having a super-stable VCO takes
a bit of the warmth out of a modular synth?

--LH--
I say no.  if there is to be any inaccuracy I would rather add it in.
remember, a VCO cannot be too accurate / stable.  You can always make a
great one less great.  But, you can never make a shitty one as good as you
want it to me.

From: <sucrosemusic@...>
Regardless of the goofiness factor, I think an accurate, selector-
type module to reside next to the VCO would be neat.  It could even
have two identical sections.  All it would need (for a basic unit)
would be 4 selectors, 2 CV ins and 2 CV outs.

--LH--
So how many do you want to buy?
Larry Hendry
www.wiseguysynth.com

hello all,

i remember this thread from the gas station (i think)
i know it's not really a point for discussion here cos paul would never in a
million years design a vco with built in instabilities - but maybe there's a
good single module patch for something subtle - like a 101 sample & hold
with level set to 1, maybe also running an 820 for random lag, into a vco
with fm2 set at something like 0.1 or maybe for ease of setting up the
'drift' could be put through a fixed attenuator (like the 822 set
to -oct..?)

anyway, since i've gotten my Logic Audio based DAW finally up and running,
i've had a basic tuned vco patch set up for about two weeks, i've been
working on around three tracks on and off over this period, with various
filter & modulation changes going on to suit the particular track (as you
do) - it won't come as any great suprise to most members that i've not had
to tweak the tuning once in these two weeks - now that's the kind of
stability i like...
...for quick patching when you're on a roll (or the computer could crash at
any minute) i've now found i treat one vco as 'master oscillator' and i
never re-tune it, the other two get tweaked quite often for harmonic
interest

by the way - i think we really really need a quantizer - my favourite patch
at the moment uses random s&h into bank 15 / wave 15 (octaves) of the
mini-wave to power a second vco on hard sync - if you get the subtlety right
it's very good bassline fodder - such a waste when i could be using it as a
wavetable voice instead...

anyway - just my thoughts on a freezing saturday morning...

cheers
paul b

At 2:29 AM +0000 11/10/01, sucrosemusic@... wrote:
>
>The "Oscillator Helper"

Talk to Larry, he's the Stooge in charge of voltage processing :)

>Too Much Stability?

Oh not again!!

>   I've always thought that the quirkiness of analog synths is part
>of the charm.

It is, but it has less to do with VCO instability than you might think.

>I'm almost wondering if there's a tangible difference
>between a nearly perfect VCO and a Digitally Controlled one.

Yes, there are tangible differences in the way changes in frequency can be
implemented.  A VCO has an infinite number of frequencies.  A DCO has a
finite number of frequencies.  In many synths, including any analogue synth
with MIDI, you have an analogue VCO controlled by the output of a DA
converter.  In some cases the VCO is controlled entirely by the DA (eg.
Matrix 12), and in other cases it receives a mix of DA output and analogue
modulation, including analogue portamento (eg. SH-101).

>Don't confused DCO with DO, though.  My understanding (which might be
>flawed) is that a DCO is an analog oscillator tightly paired with a
>digital circuit that maintains the tuning of the oscillator, while a
>DO is just a digital oscillator, using a DAC I guess.

A DCO may be defined as an analog oscillator synced to a digital clock
(Roland calls this a "rectangular of audio frequency" :).  You have a
digital master oscillator that is divided to clock analogue "oscillators".

Apparently, I don't like DCO's since I've sold every DCO synth I've ever
had (Juno 106, Juno 60, Matrix 6, MKS-10, etc.).  Then again, I've never
owned an EDP Wasp.

Otoh, you can have set of twelve analogue VCO's (one for the top octave of
each note) divided digitally (eg. Korg PS-3100), or a digital divider to
produce a sub-oscillator.  You can also have a wavetable driven by an
analogue VCO (eg. an MOTM-300 driving a Blacet Mini-Wave).  While I'm
typing, why is a PPG called a PPG??  If it stands for "Palm Products
Germany" wouldn't it be PPD??

I don't think the term "DO" is ever used, and many digital synths do not
even have a part that functions as a VCO.

>So back to the point, if these VCOs are so stable, what's the difference
>>between using them and using a DCO?  Wouldn't it be more practical
>>(although some purists would be mad) to have a modular, voltage
>controlled
>DCO?  Ahh, there's a problem there, I see, since you couldn't have
>the unit really respond to a CV signal for tuning, since the digital
>circuit wouldn't know where to tune it to be "correct"... although
>you could do it anyway (on the assumption that the Midi->CV converter
>or your CV keyboard is 100% accurate), or just have a MIDI equipped
>DCO.

Listen, you can get a MIDI controlled DCO in a number of polysynths, but it
has no place in a modular!!  In order to have a DCO module, you would need
a master clock (using a crystal or somesuch), an AD converter for every CV
input, a CPU to process all of this data, a system of clock dividers, and
the analogue circuitry required to generate the different waveshapes.
After all that, it would be much more expensive and still inferior to a
free-running analogue VCO.  Worse for more money is just bad engineering.

>Anyway, I'm not saying that I prefer DCOs at all.  I just wonder if
>having a super-stable VCO takes a bit of the warmth out of a modular
>synth?  Again, I'm not sure just HOW stable these VCOs are, if they
>vary by +/- .5 hz

If they varied by that much they'd be useless for FM and bass patches.

>then that's one thing, but if it's +/- .001 hz it's
>another.  So, if these VCOs are uber-stable, why not add a goofiness
>factor to the unit I made above, controllable with a pot, CV control
>being probably quite useless.

You can add "goofiness" by modulating the VCO with a random voltage.

When you want a really fuzzy, detuned sound for a patch, try some or 
all of these tips:

1. Keyboard gate into S&H EXT CLK, S&H OUT to one VCO's FM IN. Now 
you have a new random tuning variation with each new note. Set it as 
subtle or as wild as you like.

2. Modulate your VCO with noise. Adjust subtlety to taste.

3. Got a DarkStar? Did you do my noise clock output mod? No? Shame on 
you! This output makes an ideal signal for subtle tuning 
fluctuations - it's my favorite. Crank the CLOCK and FILTER controls 
down low to get a slow random signal with tuneable speed and lag.

Moe