[sdiy] Making an arpeggiator using CGS pedalboard and sequencer?

[Jerry Gray-Eskue]

<<At each of these
latches is a D/A converter like on the Pedal Board module.>>
<<I have scads of 74LS373's and the like. Come to think of it
the voltage wouldn't be right. Is there a better CMOS part than the CD4044
for a latch that can do 15V?>>

Looking at Ken Stones CGS10 schematic you should be able to use the 5 volt
parts.

In the description Ken says "Adjustments are provided for Tune and Span, so
the output can be zeroed, and the span set to 1 volt per octave."
You can increase the gain of the "Span" op amp to make up for the lower
voltage input. Ken has his setup at a mid range gain of 1, with the 74c922
running at +15V, so at +5V for the 74ls373 you probably need a midrange gain
of 3.

- Jerry



-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of anthony
Sent: Friday, March 26, 2010 12:41 PM
To: Synth-diy at dropmix.xs4all.nl
Subject: [sdiy] Making an arpeggiator using CGS pedalboard and
sequencer?


I think I may have mentioned this before, but maybe didn't check back for a
reply in a timely manner. My health often keeps me away from my computer -
at least for synth-DIY posts. (Ironic I know, I usually sit looking at
schematics in bed when I'm sickly...).

But an idea that stuck in my brain keeps coming up. A relatively simple
arpeggiator using a few of Ken Stone's CGS modules and some extra circuitry
I haven't quite ironed out yet. It's basically a series of latches that hold
the value of the 74C922 based Pedal Board unit and the Gate Sequencer. As
you press a key another note is pushed into another latch. At each of these
latches is a D/A converter like on the Pedal Board module. The Gate
Sequencer would be the simplest way to cycle the notes held in the latches,
but somethig more dedicated to the task might be better. As I see it the
number of steps would be simply dictated by how many notes you hit and this
should be able to automatically select itself. Some sort of counter would
work. Once the maximum notes is reached, the first note is purged, etc. A
provision should be made to reduce the number of steps in a simple manner,
in the case of a full set of maximum steps and you suddenly want fewer
steps.

I have two 74C923's and I'm hoping these will translate well. They're
basically the same thing as the 922, except you might be able to have more
notes.

I wouldn't have thought of doing an analog arpeggiator this way, if it
hadn't been for Ken Stone's cool Pedal Board Controller.

I've thought about using CD4044's as the latches, but I don't have very
many. Would something like a 74HC373 be a better choice? I have scads of
those. Well... I have scads of 74LS373's and the like. Come to think of it
the voltage wouldn't be right. Is there a better CMOS part than the CD4044
for a latch that can do 15V? There's the CD4043, but it seems less like what
I'd want than the 4044.

The key points seem to be the latch, loading the latches and moving them
along. The way Ken Stone uses the 74C922 seems to make this feel like almost
a no-brainer, but... I need brains.

Cheers,
Anthony


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