[sdiy] Building an Ondes Martinot or French Connectionstylecontroller?

Tue Dec 4 23:48:08 CET 2007

Thanks Mike, definitely a neat solution!

I'm still thinking about just using a bourns 10-turn pot
(http://www.bourns.com/pdfs/3540.pdf). The "hybitron" ones are rated
for 5,000,000 revolutions and essentially infinite resolution. I've
tested a regular wire-wound 10-turn pot and it's resolution caused
absolutely no audible (or noticeable with a tuner) 'stepping' when
used to sweep 4-5 octaves.

Mike

On Dec 4, 2007 7:30 AM, Mike <profpep at hotmail.com> wrote:
> 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
> > > > > >http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > > > > >
> > > > >
> _______________________________________________________________________
> > > > > 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
> > > > _______________________________________________
> > > > Synth-diy mailing list
> > > > Synth-diy at dropmix.xs4all.nl
> > > > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > > >
> > >
> > >
> >
>
>

-- 
Mike Beauchamp
Cross Canada Project: http://mikebeauchamp.com/crosscanada
Personal: http://mikebeauchamp.com
Business: http://therevox.com
Windsor News: http://windsorinb.relyon.ca