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Subject: Re: [motm] MOTM DIY - Was: List OK?

From: Nathan Alan Hunsicker <nate@...>
Date: 2000-06-29

I wonder how hard it would be modify a module like that to effect the
scaling not the offset. a module that could switch tracking on the fly
to control a filter (kinda like the moogs had 1/3, 2/3 and full) -Nate

"J. Larry Hendry" wrote:

> ----- Original Message -----
> From: thomas white <djthomaswhite@...>
> I haven't got any MOTM list messages for some time now.
> Is the list OK or did I get dropped or something?
> ------------------
> Yes, Thomas, the list appears to be OK. It is suffering from a case
> of
> "everybody doing something else" I guess. Since the list is quiet and
> I
> cannot be therefore accused of hogging the bandwidth (something I am
> very
> good at), I will share my latest DIY addition to my MOTM system. This
> is my
> second project to be completely finished into a final assembly on MOTM
> proto-board. I am having so much fun doing this, I just ordered a
> "pile-o-proto boards" from Paul so I can do some more (utility type
> stuff).
> This module is a manually controlled pitch shifter. I started to make
> this
> just an octave switch, as I wanted a way to shift octaves and maybe
> 5ths
> between my MOTM oscillators without having to retune them. I just
> like
> having octave switches on an oscillator. BUT, the MOTM-300's pot
> control
> offers more range and I did not want to even THINK about modifying the
> greatest oscillator module on the planet. So, my original plan was to
> make
> a module that put out a selection of fixed voltages that could be
> connected
> to one of the FM inputs of the MOTM-300 to provide this feature (real
> simple
> stuff). There was some discussion on the list. However, Ken Tkacs
> twisted
> my arm around my back (a neat trick via e-mail) and told me my plan
> should
> be modified so that the 1 volt/oct voltage keyboard CV connects to my
> module, and then my module connects to the MOTM-300 or any 1 volt-oct
> VCO.
> After first dismissing this as too difficult for a guy with a business
> degree, I finally admitted Ken was right (like he almost always is
> BTW), and
> adopted his concept for my project.
> The result is a 1U utility module with three rotary switches for
> interval
> selection and six 1/4 jacks (3 CV IN, 3 CV OUT). Each interval switch
> can
> be used separately, or all outputs controlled by the same keyboard CV
> (normalled a to b, b, to c). This simple circuit adds the selected
> voltage
> interval to the incoming keyboard CV and that is the output. This
> first
> version has 5 interval shifts up and 5 down. There are three channels
> of
> shift. The interval shift amount is completely "user selectable" by
> the
> fixed resistor selection in a corner or the circuit board (when
> building).
> I was going to use only octaves and 5ths. But along the way with my
> experimenting, I found many other useful and interesting harmonics
> (Thanks
> Ken)
> So, you hook your keyboard CV to the input of the module. You hook
> this
> module's CV outputs (3) to the 1-volt-oct inputs of your oscillators
> and
> tune all the oscillators in unison (at the high end of the CV range
> BTW).
> Then you can use the rotary switches to shift the intervals between
> oscillators. Of course, one oscillator (your fundamental frequency)
> does
> not need to pass through this module. I have the module constructed
> and
> tuned and it works quite well.
> Version # 2 of this module, will feature only 2 channels of shifting
> (yes,
> we can get by with 3 oscillators per voice). However, it will have
> more shifting capability. It will have 4 rotary switches and 4 jacks
> (2 CV
> IN and 2 CV OUT). The difference is that ANY semitone interval is
> selectable. Since each shift channel has 2 switches, one will select
> octaves up and one octaves down. The other will select intervals in
> semitones +1 through +11. So, no user interval choice will be
> required when
> building. Version # 2 is layed out on paper proto board but will not
> be
> tested and functional for about a month. I am taking a 2 week
> vacation to
> the Washington, Idaho, Montana and Calgary, Canada. So, I will start
> constructing it when I get back.
> Obviously, these are simple circuits consisting of resistor voltage
> dividers
> for interval voltages and op amps for DC adding. The trick has been
> getting
> the accuracy in the 1 volt/oct CV. If anyone has any additional
> interest in
> either of these two utility modules, please e-mail me off list. I
> don't
> want to turn the MOTM list into DIY discussion for the many that don't
> build. However, since this is created in the MOTM format for use with
> I wanted to share it with the list.
> Thanks to Ken Tkacs for his inspiration and to Paul for answering the
> one
> hundered stupid Stooge-like questions.
> Larry Hendry
> Disclaimer: I am not a BS/MSEE. I am not a design engineer. This is
> learning stuff. My only claims are that:
> 1 - I am having fun
> 2 - My circuit works very well
> 3 - I am buying more MOTM proto boards than anyone else.
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