[sdiy] Bar Graph Driver as Quantanizer

[Kyle Stephens]

Just waiting for the 3914s to arrive to start experimenting!

One good point Roy brought up was that the 3914 puts out currents not voltages. Would the Schmitt triggers clear that up, or need I use an LED (say, an opto-FET switch tied to a 1 volt voltage reference) to get back to voltages?


_Kyle


--- On Mon, 2/2/09, Tim Parkhurst <tim.parkhurst at gmail.com> wrote:

> From: Tim Parkhurst <tim.parkhurst at gmail.com>
> Subject: Re: [sdiy] Bar Graph Driver as Quantanizer
> To: lightburnx at yahoo.com
> Date: Monday, February 2, 2009, 12:57 PM
> Hey Kyle,
> 
> I've been thinking about various applications for the
> 3914, and I've found a
> few on the interweb, but I've been so swamped with
> other Magic Smoke
> business that I really haven't had a chance to try any
> of them out! Of
> course, you have the various audio level and voltmeter
> applications, along
> with Ian's 5 Pulser and Grant's Analog Tracking
> Generator. I was also
> thinking you could do a sequencer (with voltage control of
> stage and
> direction), a quantizer, and a three 'window
> generator' where you put in a 0
> to 10V ramp and get out three voltages that rise and fall
> at evenly spaced
> intervals (apply those voltages to three VCAs and you could
> smoothly fade
> between the three VCA outputs). The 'window
> generator' is somewhat related
> to Grant's design, but with multiple outputs. Other
> than that, I was
> thinking of enhancements like adding trigger outs at each
> stage and maybe
> some other goofy stuff like that. If you do knock together
> a 3914-based
> quantizer, let me know how it works out!
> Tim (Servo) Parkhurst
> On Sat, Jan 31, 2009 at 10:02 PM, Kyle Stephens
> <lightburnx at yahoo.com>wrote:
> 
> > After I sent off the email, I thought of the 3x LM3914
> idea too after I had
> > some more time to ponder :)
> >
> > Just took a look at the Oberheim (available here if
> anyone else is curious:
> >
> http://www.crowncity.net/ratcave/Electro/Oberheim/Mini_Seq.jpg),
> and I
> > know about the MFOS quantinizer, and there's one
> by Scott Stites too (
> >
> http://mypeoplepc.com/members/scottnoanh/birthofasynth/id15.html),
> but
> > like you said, there's fun to be had.
> >
> > Hmm. What have you wrung out of the 3914 so far? I got
> wind of it through
> > an Ian Fritz design, the 5pulser (
> > http://home.comcast.net/~ijfritz/sy_cir8.htm).
> >
> >
> > _Kyle
> >
> > --- On Sat, 1/31/09, Tim Parkhurst
> <tim.parkhurst at gmail.com> wrote:
> >
> > > From: Tim Parkhurst
> <tim.parkhurst at gmail.com>
> > > Subject: Re: [sdiy] Bar Graph Driver as
> Quantanizer
> > > To: lightburnx at yahoo.com
> > > Cc: "Synth-DIY"
> <synth-diy at dropmix.xs4all.nl>
> > > Date: Saturday, January 31, 2009, 8:55 PM
> >  > On Sat, Jan 31, 2009 at 8:00 PM, Kyle Stephens
> > > <lightburnx at yahoo.com> wrote:
> > >
> > > > Some musings...
> > > >
> > > > While looking at the LM3914, a bar/dot graph
> driver, I
> > > realized that it's
> > > > basically a quantinizer. With a few tweaks
> and a
> > > stable voltage reference,
> > > > it'd serve as such. I think... Help me
> here if
> > > otherwise.
> > > >
> > > > Datasheet's here for reference:
> > > http://www.national.com/ds/LM/LM3914.pdf
> > > >
> > > > One big question, is how could I use just 2
> chips(*)
> > > for several octaves
> > > > (vs. 1 chip per 10 notes...?). Some kind of
> dynamic
> > > reference voltage
> > > > offset...? Not unless that's not a
> completely
> > > unreasonable solution. The
> > > > datasheet says you can chain together up to
> 100
> > > outputs. With 12 discrete
> > > > keys per octave, that's 100/12 =
> effectively 8
> > > octaves.
> > > >
> > > > (*) At least 2 chips would have to be
> employed anyway,
> > > as they only have 10
> > > > outputs each. So, call it 2 chained ICs for
> 20 total
> > > outputs, 12 of which
> > > > would be used for 12 "bits" of
> > > resolution/levels of quantification. That's
> > > > assuming the "just 2 chips"
> configuration is
> > > possible, otherwise it's just a
> > > > step-after-another progression.
> > > >
> > > > There's also the LP3943, which has 16
> outputs to
> > > start with. It's a low
> > > > power IC though - has that any share of
> potential
> > > issues?
> > > >
> > > > Datasheet:
> http://www.national.com/ds/LP/LP3943.pdf
> > > >
> > > >
> > > > The 3194 has a 'bar' and
> 'dot' mode;
> > > bar is 'from ground up,' with each
> > > > output giving a fixed voltage, which when
> summed would
> > > give you the
> > > > quantinized CV.
> > > >
> > > > Switch to dot mode, which triggers the
> output
> > > designated closest to the
> > > > input voltage, and you got a voltage
> controlled event
> > > generator; between
> > > > your preset step range (dunno the exact
> hysteresis
> > > thereof...), gate 'a'
> > > > fires, next step gate 'b', etc.
> > > >
> > > > On the note of hysteresis, I looked it up in
> the
> > > datasheet just now and it
> > > > said there isn't any built in, and
> there's a
> > > fadeover of 1mV or more between
> > > > outputs (apparently less if the next
> "step"
> > > isn't on the same IC, for
> > > > chained circuits). I'm not sure how to
> address
> > > that... A comparator, or a
> > > > specific output-voltage referenced Schmitt
> trigger,
> > > per output??
> > > > (x12 is kinda steep). How many cents off
> would ~1mV
> > > bend a VCO anyway?
> > > >
> > > > Any other thoughts on this? And again, is it
> even an
> > > effective, let alone
> > > > feasible idea? Just wana scope things out
> before I hit
> > > the breadboard.
> > > >
> > > >
> > > > Also: a grateful if belated thank you to
> everyone who
> > > responded about my
> > > > MS-20 filter clone questions!
> > > >
> > > >
> > > > _Kyle
> > > >
> > > > (whoops, meant to send this to Kyle AND the
> list...)
> > > Hey Kyle,
> > >
> > > The 3914 is an interesting chip. I'm putting
> together
> > > some 3914 based stuff
> > > for a "Making Music With the 3914" book
> I want to
> > > write... some day. In any
> > > case, I haven't made a quantizer with the
> little
> > > buggers yet, but my
> > > thoughts are: Use three chips - the first is the
> Octave
> > > Quantizer and is set
> > > up to quantize to the nearest whole volt value,
> and
> > > subtract the ouput of
> > > that from the input so that you're left with
> a CV that
> > > varies from 0 to 1V
> > > (e.g., 1.23V in = 0.23V out, 3.75V in = 0.75V
> out). The 0
> > > to 1V signal goes
> > > into the Note Quantizer made from two 3914s
> chained
> > > together (and adjusted
> > > so that you're only using the first 12
> outputs). All of
> > > the 3914 outputs
> > > drive 40106 schmitt trigger inverters. This makes
> it so
> > > that the selected
> > > 3914 out goes high, and should eliminate any
> problems with
> > > the 'fadeover'
> > > causing more that one out being on at a time.
> Combine the
> > > output of the
> > > first 3914 (the Octave) with the output of the
> Octave
> > > Quantizer and the Note
> > > Quantizer, and Bob's yer uncle, you've
> got a
> > > 3914-based quantizer.
> > >
> > > To sum it up; one chip quantizes to the nearest
> octave,
> > > another two chips
> > > quantize to the nearest note within one octave,
> and then
> > > you combine the
> > > outputs. In theory, you should be able to get 10
> octaves
> > > with three 3914s,
> > > four 40106 inverters, a handful of op amps, and
> maybe a
> > > couple of voltage
> > > reference chips or zeners. You'll probably
> also need
> > > several trimmers and /
> > > or precision resistors for setting up voltage
> dividers.
> > > Might be easier to
> > > go with the standard Counter-D/A-Comparator type
> of
> > > quantizer, but where's
> > > the fun in that? ;-)
> > >
> > > (If you want a potentially quicker solution,
> check things
> > > like the Oberheim
> > > mini-sequencer, or I think Ray Wilson has a nice
> updated
> > > version complete
> > > with a PCB for purchase)
> > >
> > >
> > > Tim (proud owner of a tube full of 3914s) Servo
> > > --
> > > "A nation cannot prosper long, when it
> favours only
> > > the prosperous." -
> > > Barack Obama
> >
> >
> >
> >
> 
> 
> -- 
> "A nation cannot prosper long, when it favours only
> the prosperous." -
> Barack Obama