On 2009-05-28 08:45 +0200, JH. wrote:
> I've ordered the boards from the factory already, but I always
> get more than I've ordered (and have to pay them: small print of
> contract that I have to take over-production),
Interesting commercial practice.
> >Personally, I'm not sure about this modulation source. I suspect
> >that, on my unit, the waveform pot would be permanently stuck in
> >pure sine position, making the scanner redundant.
>
> I am ∗very∗ sure about this modulation source, because I came to
> love it in my JH-4 synthesizer module over many years.
> Don't under-estimate the Sample&Hold modulation on a phaser with
> high resonance! And this is a very special S&H, with a kind of
> overshot or spike (for lack of better description) at the
> beginning of each new random sample, which makes the S&H more
> "agressive" than a "perfect" S&H would be.
> But there is more:
> The waveform crossfading ("scanner") is arranged ina way that
> S&H is adjoining "square" on the left side, and
> "self-modulation" on the right side. That means, in S&H position
> you have true random staircases. Turn the waveform pot slightly
> to the left, and you get a tad of regular rectangle mixed in:
> the steps become less random in a way that large steps are more
> likely. Turn the waveform pot slightly to the right, and the
> random S&H gets mixed with the dirt of an audio-rate
> self-modulated filter. That's especially impressive at high
> resonance settings. I got the idea for this from the Prophet 5's
> Poly-Modulation and the CS-50's and Minimoog's external
> modulation input, and - for a phaser application - from the EMS
> Synthi HiFli.
Thanks for the explanations. Where does the self modulation comes
from ? lfo_mod seems to be in the wrong direction. Perhaps AUX
MOD IN should be normalled to something else than ground ?
> >The other sources I see myself using (velocity, EG and sawtooth
> >LFO) all have to come from other modules anyway.
>
> Yes, it makes a lot of sense to use external modualtion sources.
> My on-board modulation source is kind of special (I hope!), but
> it doesn't have saw waveforms, for instance.
Seen from here, it's plenty special. :-)
> >In theory, each pole could individually be switched between
> >all-pass (phaser) and low-pass (filter) under voltage control. If
> >all poles are sonically interchangeable, a single CV could be
> >used with the number of LP poles being 6/5 of the CV. No idea how
> >to do that, nor how useful it would be.
>
> I'm not entirely sure if I understand what you mean.
This is what I had in mind :
CVPole 1Pole 2Pole 3Pole 4Pole 5Pole 6
~ 0.42 VLPLPLPLPLPLP
0.42 V ~ 1.25 VLPLPLPLPLPAP
1.25 V ~ 2.08 VLPLPLPLPAPAP
2.08 V ~ 2.92 VLPLPLPAPAPAP
2.92 V ~ 3.75 VLPLPAPAPAPAP
3.75 V ~ 4.58 VLPAPAPAPAPAP
4.58 V ~ APAPAPAPAPAP
The idea is that the higher the CV, the more high frequency
content there is.
Looks like it could be done with an LM3914-type circuit.
> But the 6 stages are interchangeable only with the "Slope" (or
> pole spread) potentiometer at ccw position. When the poles are
> spread apart, it makes a difference which one gets the
> complementary zero (= switchet to all pass), and which one
> doesn't.
Okay, so there are not 7 but 2∗∗6 = 64 combinations. I can't think
of a way to map this six-dimensional space to a scalar. Not one
that would be acoustically intuitive, anyway.
Ordering the combinations by amount of HF energy is not
straightforward because a combination that has more HF than
another when the first pole is at 100 Hz might have less when it's
at 5 kHz or vice-versa.
Ditto for ordering by response at 20 kHz (or any other fixed
frequency).
--
André Majorel <URL:
http://www.teaser.fr/~amajorel/>