[sdiy] Clarification on Breath Controller Q

[Theo]

Yep, you're right :)
The DX7 circuits show how it could be done, its on that german "rip-off"
site from the other day.
Page two on the bottom.

Theo

From: The Old Crow <oldcrow at oldcrows.net>



>
> On Tue, 31 Jul 2001 gmuir at sympatico.ca wrote:
>
> > I did want to clarify my original question a bit. I realize that you
> > can simply feed a BC-1 or BC-2 signal through a DX and run that MIDI
> > CC through a MIDI to CV converter, but what I am looking to do is keep
> > the signal from the BC in the ANALOG domain (a la CS-01) to avoid
> > unnecessary quantization of the control voltage during the conversion
> > process(as many have described in their experiments).
> >
> > My guess is that one of the pins on the BC plug takes a voltage from
> > one of the rails, which powers the internal circuitry, and that
> > another pin feeds the synthesizer with a steady CV (which in the case
> > of a DX gets sampled into the digital domain and integrated with the
> > outgoing MIDI data).
>
> > Does anyone have any ideas?
>
>   I think the BC-1 is a passive device: a (resistive) pressure sensor and
> a trimpot.  IIRC the tip-center-ring of the mini phone plug goes like
> this, but I'll have to look at the schematic at home later to be sure:
>
>   Tip: CV out, goes from +V to ground.
>
>   Center: +V input to the top end of the sensor.  I think the trimpot is
> in series with +V, but it has been years since I looked inside a BC-1.  I
> think the DX7 used +V = +5V.
>
>   Ring: Common/ground.
>
>   A DX7 would just feed the CV to one channel of an A/D chip and digitize
> it at regular intervals.  For analog use, just need a simple circuit of 1
> or 2 op-amps to span and zero the CV to whatever range you want.
>
> Crow
>
> /**/
>