[sdiy] breath control lfo hack

[jiles]

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!