[sdiy] breath control lfo hack

[vitreousflux]

I added a custom LFO to my minikorg awhile back, Using the ASM1 LFO
schematic. It simply controls the CV for the filter cutoff levels.  The
schematic could be easily modified to work with the BC1 input. A couple
work-in-progress pictures (outside the chassis only, sorry) at
http://zap.to/vitreousflux .

You could also use Tom G's SBM LFO circuit, it is a wonderful, simple,
flexible LFO, more powerful than the ASM1 stock circuit. Just breadboard the
components and use your meter along with resistor and pot swapping to get a
suitable voltage. Then wire away!

I will say this: IMO many digital synths aren't really worth messing with in
this much detail (that is: adding analog circuitry to control digital
synthesis) when the synth will quantize the incoming voltage to 128 steps
anyhow. I would recommend simply using a computer and midi software to
approximate or sequence this CC2 LFO instead. Could also use a midi
controller like the Peavey, Kenton or Drehbank boxes.

If you ask Harry and say pretty please with sugar on top, he might draw you
a circuit........


Rob



----- Original Message -----
From: "jiles" <jb at dezzanet.net.au>
To: <synth-diy at node12b53.a2000.nl>
Sent: Friday, June 08, 2001 2:04 AM
Subject: [sdiy] breath control lfo hack


> hi all!
> i'm very much a newbie with electronics, but i want to do this breath
> control hack.  it does represent a significant jump for me, but i figure
it
> would be a good way to educate myself, i'm not expecting to built this
> thing overnight; it will take time, i'll have to read some electronics
> books.  but i thought i'd throw the idea out here to get some feedback and
> some pointers of where i go from here.
>
> i've been mucking around with the breath control input on my dx100.  it
was
> designed to be used with BC1 controller.  there was also a BC2, possibly
> others.  i know some other fm synths used BC1, i think the CS01 did too.
> i've made a simple pot to replace the BC1. on the dx100 it can be assigned
> to control pitch modulation depth, amplitude modulation depth, pitch,
> operator output (ie either carrier or modulator).  i also made a switch to
> plug into the foot switch socket on the dx, you can assign that to control
> portamento on/off or sustain on/off.
>
> my next step was going to be to install these into a box, but i've got
this
> idea of adding an LFO that would also be sent to the breath controller
> socket.  to me this opens up some really interesting possibilities!  it
> would be nice for live performance.  also the stuff going into the breath
> control socket is sent out the midi out port as CC#2, so it can all be
> recorded into a sequencer.  this idea is probably best suited for making
> weird noisier stuff rather then melodic stuff, but that's the sort of
thing
> i love doing with my dx.
>
> here is a table of what you could do with the lfo:
>
> parameter name...what it controls.............applying the external lfo
> would result in this
>
> pitch            pitch modulation depth       self explanatory!
> amplitude        amplitude modulation depth   self explanatory!
> pitch bias       pitch                        adds 2nd pitch modulation to
> the dx *1
> eg bias *2       operator output level        adds 2nd amplitude
modulation
> to the dx
> eg bias *3       operator output level        the fm equivalent of filter
> modulationoisier
>
> *1 the modulation would not hover around the center frequency but could
> either go up or down from the center frequency, depending on the setting
on
> the dx.
> *2 assigned to a carrier
> *3 assigned to an operator
>
> this is a run down of how BC1 compatible stuff works that i found on the
web:
>
> --------------------------------------------------------------------------
--
> ------------
>  _____                          _____
> |     |-ring-------------------| 50K |
> |jack |-tip--------------wiper-| pot |
> |_____|-sleeve-----------------|_____|
>
> Once you make it, just connect a male-male stereo plug into both the DX27S
> and this box, and you are ready to go.
>
> In other words: The DX27S sends a voltage down the top (tip) connector of
a
> stereo 1/8" plug used for the breath control. The modulation is controlled
> by the bottom (ring) connector that it receives back. The sleeve is
ground.
> So, you are essentially in this circuit controlling the voltage via a
> simple pot.
>
> Experiment with the values. I used a 50K linear (because of Radio Shack's
> limited parts supply), and it's a bit coarse. I think a 50K audio would be
> best, but I haven't experimented too much. I'm happy with my new toy. (:
> --------------------------------------------------------------------------
--
> ------------
>
> i believe it is 5 volts that gets sent out.
>
> so it appears my LFO idea could be done in 2 ways:
>
> 1. you have an LFO that sweeps between 0 ohms and 50K (or whatever the
> correct value is) this then gets applied to the 5 volts coming in to sweep
> it from 0V to 5V.
>
> 2. the LFO just produces the voltage itself, again from 0V to 5V and that
> gets sent to the dx.
>
> the controls i'd want are waveform (preferably including S/H), rate,
depth.
>
> has anybody on the list done this before, either with bc stuff or any
other
> sort of pedal input?
> which method would be easiest number 1 or 2?
> is there an LFO IC being made now?
> if not anyone know of any resources on the net for building an LFO?
>
> thanks for any help in advance!  i will let the list know developments,
> also maybe when i finish the project i'll make a site explaining how to do
> it all.
>
> cheers!
>
>