MOTM

I went through and sized up the resistors that were required to actually
change out the VCO course tune pot to an 11 position octave switch
(actually hitting the 5ths in between).  I'll see if I can dig that up.  I
have not modified one of mine yet, but I have considering it a couple of
times.  I was going to use the best trimmers I could get and just preset
the switch for octaves and 5ths.  The 12 position was going to short out
part of the resistance in the "fine tune" summing resistor so a "course"
variable adjustment could still be available there.

These are just THOUGHTS, not plans.
"Standard dumb stooge disclaimer applies"

However, once Paul actually makes that highly accurate DC mixer, it would
be easy to mix the incoming 1/volt per octave voltage with one from your
resistor divider.  However, now that I think about it, here is a decent
idea:

Use one of the FM inputs to do your octave switching.  Since they are not
1/v octave, some measurement would need to determine what voltage produced
the octave shift desired with the predetermined FM knob in the 100%
position.  Once the voltages were determined, you could build a simple
voltage divider with trimmers, and a rotary switch to select octaves up or
down and do the whole thing without any modification to the best VCO on the
planet.

In fact, I like this idea.  I am gonna take some measurements myself and
see what gives.

Great idea Nathan.  A simple 1U panel could be made up with up to 4 rotary
switches and 4 output jacks so you could add octave switching anytime you
wanted by just plugging in.  However, I think I would only put about 2 in a
panel and make the trimmers (front panel accessible).  They make very nice
panel mount holders for those 15 turn trimmers that look very nice.  And
trimming necessary could be easily done.

Larry (off to experiment) Hendry


----------
> From: Nathan Hunsicker <nate@...>
> To: MOTM Newsgroup <motm@onelist.com>
> Subject: [motm] Osc Controller
> Date: Wednesday, March 15, 2000 9:20 PM
> 
> From: Nathan Hunsicker <nate@...>
> 
> Does anyone know a simple circuit I could build to drop an input voltage
> in 1 volt steps. What I want to do is build an oscillator controller to
> switch octaves by flipping a series of switches or by turning a rotary
> switch. I'd like to be able to tune all my VCO's the same and then use
> this unit to lower the pitch by octaves, similar to the footage switch
> on a moog 921. Is this possible? -Nate
> 
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