[sdiy] Building an Ondes Martinot or French Connectionstylecontroller?

Tue Dec 4 13:30:09 CET 2007

Dear Mike

I've just remembered a cheapskate possibility for this, based on a tremolo
design from the early 70's.

How about this: a polarised light opto. Buy some light polarising plastic as
used in 3D glasses etc, ( know a self adhesive film is available, it's a
staple part of LCD displays. Arrange a light source in front of a CDS
photcell, and put a payer of polariser over the cell. In the gap between the
cell and the source, have a clear rotating disc with a layer of polariser on
it. As the disc turns, the angle between the polarisers will go, (once set
up), from 0 to 90 degrees, and the light transmission willchange from
roughly 100% to none.

In the design I built, the disc was spun by a variable speed motor,
producing a sine wave, 'no thump' modulation via the CDS cell, by adding
anothe light/cell pair at 90 degree around the disc to the first, we got a
panner.It isn't a true sine because of the linearity of the CDS cells, but
it worked well.

In your case, a 'dial cord' could rotate the polariser disc, and by having
the cell in a kind of clamp, it could be rotated to adjust fro max output
when the disc was at one end of it's scale.

Mechanical inertia would be low, and the system would have a very low wear.
You'd have to ask Jurgen about his choice of cells for his phaser: some have
a slow return to high reistance. resolution/repeatbility might be a problem.

I know this trick works, but it's a lot of mechanics.

Best wishes

Mike

>
> I was going to mention the radio tuner thing, as I've seen the inside
> of a few marantz, etc. I should definitely look into it more. The
> whole FM tuner with the string thing really isn't my generation.. I'll
> have to get more familiar.
>
> I was figuring the Ondes turned a variable capacitor. Thanks for
> this... I'm not trying to build and Ondes, (although as a side project
> it'd be cool to put a website up with ALL the ondes information.. like
> if a schematic came to light, etc. So other people may attempt to
> build their own).
>
> For now, I just want to build a controller that outputs a CV that uses
> an ondes-like interface. Ideally, using fairly easy to find components
> (like say, a bourns 10-turn potentiometer, etc.). I know that the
> instrument's sound has a lot to do with the strange speakers and
> resonators, etc. But, I'm not about wanting to recreate the whole
> instrument.
>
> I know the "French Connection" controller already exists
> (http://www.analoguesystems.co.uk/Reviews/fconnection_review.htm), and
> after reading about this controller on a few message boards (where
> people have opened it up), it uses exactly what you described as the
> digital solution. Shaft encoder, etc. Pretty funny that it's actually
> digital, considering it's made by "analogue systems".. but as you
> said, it's smart because there's no potentiometer to wear out
> (Although the burns 10-turn pots are rated for 10,000,000 rotations I
> believe?).
>
> Mike
>
>
>
>
> On Dec 3, 2007 6:51 AM, Mike <profpep at hotmail.com> wrote:
> >
> >
> >
> >
> > > Thanks ken, i was thinking this was a possible solution. Very cool..
> > > Is this pulley something that goes around once (so it's circumference
> > > is slightly larger than the length of the travel?) or multiple times?
> > > If the pulley goes around multiple times that means the string goes
> > > around the pulley multiple times as well, and would there be anything
> > > there to stop it from getting tangled up if 10 loops of string go
> > > around it for example?
> > >
> > You really need to look a t a few old radios. This a very common
solution to
> > the tuning dial problem, the difference here being in the gearing. A
tuning
> > dial needed several turn of a knob to move a variable capacitor through
> > roughly 180 degrees. here you are 'driving' the device by effectively
moving
> > the 'pointer'. Bang and Olufsen used a scheme light this for the 'slide
> > rule' tuning system on some of their portable radios and
tuners/receivers.
> >
> > By the way, if I remember correctly from working on one briefly, before
a
> > performance of Messians 'Turangalila Symphony', the Ondes Martenot ring
> > slider did indeed operate a variable capacitor as part of a valve
> > oscillator. This may have been a BFO type. Thinking of the technology of
the
> > day, and the radio expertise around at the time, this does seem likely.
Has
> > anyone got a pointer to an Ondes Martenot circuit diagram? By the way -
the
> > diagram alone is nowhere near enough to build one: the strange
louspeakers
> > had as much, if not more, to do with the tone. The only way I can think
of
> > to come up with a reasonable substitute is a PC based 'model' or Scott
with
> > his FPGA modelling. How to do the analysis presents a whole other
challenge.
> >
> > There are some very good, very linear, light action, 5 turn pots out
there
> > as well as 10 turn ones. I think that's where I'd start too.  If wear is
a
> > problem, then a high quality, absolute shaft encoder, a processor and an
> > A-->D might be another option. There must  be a capacitance based
solution
> > too, though I think that might take you into the exotic instrumentation
> > area.
> >
> > HTH
> >
> > Mike
> >
> >
> >
> > > On Dec 2, 2007 3:02 AM, Ken Stone <sasami at hotkey.net.au> wrote:
> > > > The string slip problem is solved by anchoring the string at the
ends to
> > the
> > > > pulley. It is not a continuous loop, but rather a long string (3
times
> > the
> > > > length of the travel + spare to cover the remaining distances
between
> > the
> > > > pully and the playing area), with a one length wound on the pully,
one
> > > > length along the keyboard, and one length returning from the other
end
> > of
> > > > the keyboard to the pulley again. Usually one end was terminated in
a
> > spring
> > > > housed within the pulley itself.
> > > >
> > > > Ken
> > > >
> > > >
> > > > >I've built a few simple portamento controllers, and I want to build
a
> > > > >sort of Ondes Martinot controller (Sort of like the Analogue
systems
> > > > >"French connection" controller -
> > > > >http://www.analoguesystems.co.uk/Reviews/fconnection_review.htm). I
> > > > >mean JUST the portamento string-ring interface, not the keyboard
> > > > >interface. If nobody's seen one before, here's a nice video
explaining
> > > > >one.. http://youtube.com/watch?v=ybYIhomm5KM
> > > > >
> > > > >I've never actually seen the inside of any of these controllers and
> > > > >I'm sort of curious as to how they might work. I'm wondering if
anyone
> > > > >has seen inside, or know exactly how they might work mechanically?
> > > > >
> > > > >My first guess would be to have the string wrap a few times around
a
> > > > >pulley wheel attached to a 10-turn potentiometer (or a geared down
> > > > >single turn pot, to avoid having a pulley wheel with a
circumference
> > > > >as long as the actual playing field area). I'm wondering if maybe
> > > > >either of these controllers came up with a way of avoiding the
string
> > > > >from "slipping" on the pulley over the course of time, or if just
> > > > >wrapping a string around a pulley multiple times would cause enough
> > > > >friction to avoid this (I'm reminded of old FM tuners, which I
THINK
> > > > >slip over time). Also, if there's something to deal with tension on
> > > > >the string.. and what kind of string it might be?
> > > > >
> > > > >The second thing (and this one is a lot more complicated in my
mind)
> > > > >is how the "button" style volume controller works. The best
solution I
> > > > >came up with brainstorming last night would be to have the button a
> > > > >miniature version of a cry-baby wah-wah pedal, but with a spring so
it
> > > > >returns to it's top position. The lever would be attached to a
geared
> > > > >shaft which would ride against the gear of a potentiometer (just
like
> > > > >in the wah wah pedal).
> > > > >
> > > > >Mike
> > > > >_______________________________________________
> > > > >Synth-diy mailing list
> > > > >Synth-diy at dropmix.xs4all.nl
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> > > > >
> > > >
_______________________________________________________________________
> > > > Ken Stone   sasami at hotkey.net.au
> > > > Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> > > > Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>
> > > >
> > > >
> > >
> > >
> > >
> > > --
> > > Mike Beauchamp
> > > Cross Canada Project: http://mikebeauchamp.com/crosscanada
> > > Personal: http://mikebeauchamp.com
> > > Business: http://therevox.com
> > > Windsor News: http://windsorinb.relyon.ca
> > > _______________________________________________
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> > >
> >
> >
>