Sujet Vco, Dco, tout numérique, j'arrive pas bien à comprendre.

Citation :
Dco, ça veut bien dire numérique, et les oscillos du matrix 6 sont numériques, c'est sur.

Citation : Si sa commande est numérique, c'est que c'est numérique

Hors sujet : je fais une bonne saison avec st etienne mais je me suis fait battre par lyon qd meme

Hors sujet : Et niveau QI ça donne quoi ?

Hors sujet : jette le, il est sûrement défectueux

Hors sujet :

Citation : Si sa commande est numérique, c'est que c'est numérique

Citation : Yes, it's an analog ramp generator which is synchronised to a digitally
generated pulse train. Each time a pulse arrives, the ramp is reset to
zero.

The pulse train would typically be generated with a counter chip such as
the Intel 8253 under processor control. Since this is a digital device,
you can only generate a finite number of frequencies. With a VCO you can
generate an _infinite_ number of frequencies because the control voltage
is analogue, i.e. continuous.

Example:

With a 2MHz master clock feeding an 8253 (16-bit) counter, we want to
generate a 440Hz tone.

Since 2e6/440 = 4545.45, we would have to feed the 8253 counter with
the value 4545 (only integers allowed). This would result in a frequency
of 2e6/4545 = 440.044 Hz, which is pretty close.

Oh, we also have to feed the ramp (sawtooth) generator with a control
voltage which determines the slope of the ramp. The CV is not critical,
because it doesn't affect the frequency of the DCO. It does affect the
amplitude, though, but that doesn't matter becuase the human ear is not
very sensitive to small changes in amplitude (as opposed to small
changes in frequency).

In other words:

The DCO produces an _analogue waveform_ whose frequency is sync'd to a
master clock through integer division.

Hope this helps a little.

-joachim

Citation : IMO, there are quite a lot of nuances of VCO-DCO. Let me try and make
the whole chain from "analogue" to "digital" (Though I wouldn't say strictly
from "good" to "bad" ;->)

(1) free running analogue oscillator, controlled by analogue voltage divider
keyboard. (Minimoog, ...)

(2) free running analogue oscillator, controlled by digital via a D/A
converter
without correction, and analogue modulation (Oberheim n-voice (?) )

(3) free running analogue oscillator, controlled by digital via a D/A
converter,
with autotune, scale correction and stuff, but still analogue modulation
(Sequencial Circuits Prophet5 rev. 3)

(4) free running analogue oscillator, controlled by digital via a D/A
converter,
with autotune, scale correction and digital LFO / Sample&Hold / Glide
modulation, but with analogue ADSR->VCO modulation (Oberheim OB-8).

(5) free running analogue oscillator, controlled by digital via a D/A
converter,
with autotune, scale correction, and all modulations including ADSR via
DAC (Sequential Prophet 600).

(6) free running analogue oscillator, controlled by digital via a D/A
converter,
with autotune, scale correction, and all modulations including ADSR via
DAC, plus automatic autotune in the background from time to time
(Oberheim Matrix12 (?)).

(7) Simple Ramp-Oscillator that is synced by a counter every cycle, but
with different clock/divider tree for both DCO's in a voice (Oberheim Matrix
6,
EDP Wasp)

(8) Simple Ramp-Oscillator, that is synced by a counter every cycle, but
with one single clock/divider tree for both DCO's in a voice (Oberheim
Matrix 1000)

(9) Staircase Waveform stuff (as described in different recent mails)

(10) Wavetable stuff (also as described in recent mails)

These are the different types I know of. Maybe there are still others in
between.
Speaking in the word's original sense, (2) - (6) would be something like
"DCVCOs" ("digital controlled VCOs") in the sense of a digital word forms
an analogue voltage that controls an oscillator. (7) and (8) would be real
"DCOs", cause they are still oscillators, only under the iron grip of
digital
clock, which makes them sound thin and lifeless. (9) and (10) shouldn't
be called "controlled oscillators" anymore, perhaps just call them "DOs"
("digital oscillators") or even closer to the point, "DDs" (digital
dividers)
or "DS's" (digital scanners). Well, but that would go too far then.

Oh, I forgot another interesting variation:
Analogue oscillators with digital dividers / waveforms:

(11) analogue VCO with dividers (some ARP-synths - thank You Joachim,
for the schematics! - and of course the Suboscillators in various VCO-
based synths)

(12) 12 analogue VCOs for the 12 top-octave-semitones and digital
dividers (Farfisa VIP 245, Korg PS-3x00 series)

JH.

Citation : ce qui compte c'est si le son te plait et pas la façon dont il est produit