RE: [sdiy] Bar Graph Driver as Quantanizer

[rdrake]

check out Grant Richter's Analog Tracking Generator... http://www.musicsynthesizer.com/DIY/Grant/CVtwister.html

bbob
www.fluxmonkey.com

>----- ------- Original Message ------- -----
>From: :lightburnx at yahoo.com
>To: synth-diy at dropmix.xs4all.nl
>Sent: Sat, 31 Jan 2009 -0800 (PST) 20:00:45
>
>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
>
>
>      
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