[sdiy] ARP Sequencers - using more than 1 ~``~

[Casio Rapman]

Hi Tim,

Thanks for the advice.  One of the multiple jacks could be used for an extra 
input without having to drill any holes, but I'm not sure if your suggestion 
would work.  I'll have to look into it. Also, the 2nd suggestion would also 
require a comparator.  And it's also a bit much, I was hoping there would be 
some more straight-forward way of doing this.  Oh well....

Hey Casio,

That's a bit of a tough one. What the ARP does is use a sawtooth VCO as its 
clock gen. The saw wave is fed to a comparator that creates the variable 
width clock pulse (a very basic PWM circuit). I think you could accomplish 
what you're talking about by taking the saw wave out of the master sequencer 
and feeding it into the PWM circuit of the second sequencer. Then you could 
have both sequencers driven by one clock, but with the ability to set the 
clock pulse width seperately for each sequencer. You'd have to add a couple 
of jacks to the existing sequencers (saw out, pulse comparator in), but the 
mods shouldn't be too difficult. Another possible solution would be to use 
an external saw VCO (set to low frequency operation of course) and two 
external PWM circuits. Then, you just feed the output of each PWM circuit 
into clock input of one of the sequencers.

You can find the schematics at http://www.retrosynth.com/docs/1601/

I've noted that a lot of analog sequencers don't have a variable width clock 
pulse. How critical is this? I've studied the ARP 1601 intending to clone it 
(project #10 on a list of about 40), but sadly, it's been years since I've 
actually used one (and then only briefly). Is this a "top-five useful 
feature", or is simply fiddling with envelope settings enough?

BTW, you're lucky enough to own TWO ARP sequencers? ;) Congrats!




>From: Tim Parkhurst <tim.parkhurst at gmail.com>
>Reply-To: tim.parkhurst at gmail.com
>To: Casio Rapman <casiorapman at hotmail.com>
>CC: analogue at hyperreal.org, synth-diy at dropmix.xs4all.nl
>Subject: Re: [sdiy] ARP Sequencers - using more than 1
>Date: Sun, 18 Sep 2005 13:37:30 -0700
>
>On 9/15/05, Casio Rapman <casiorapman at hotmail.com> wrote:
>
> > Here's a question for ARP Sequencer users.
> > Is it possible to synchronize multiple ARP sequencers to the same clock
> > and
> > have each of them output a its own voltage controlled clocked gate 1
> > output
> > with its own independently varying voltage controlled pulse width (for
> > varying gate lengths)?
> > It seems to me like the sequencer providing the master clock is the only
> > one
> > which can have CV control of the gate width coming from this clocked 
>gate
> > 1
> > output.
> > Am I wrong? If I'm right, is there any way to modify an ARP sequencer to
> > do
> > what I want?
> > Thanks!
> >
> > _________________________________________________________________
> > Is your PC infected? Get a FREE online computer virus scan from 
>McAfee(r)
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> >
> >
>  Hey Casio,
>  That's a bit of a tough one. What the ARP does is use a sawtooth VCO as 
>its
>clock gen. The saw wave is fed to a comparator that creates the variable
>width clock pulse (a very basic PWM circuit). I think you could accomplish
>what you're talking about by taking the saw wave out of the master 
>sequencer
>and feeding it into the PWM circuit of the second sequencer. Then you could
>have both sequencers driven by one clock, but with the ability to set the
>clock pulse width seperately for each sequencer. You'd have to add a couple
>of jacks to the existing sequencers (saw out, pulse comparator in), but the
>mods shouldn't be too difficult. Another possible solution would be to use
>an external saw VCO (set to low frequency operation of course) and two
>external PWM circuits. Then, you just feed the output of each PWM circuit
>into clock input of one of the sequencers.
>  You can find the schematics at http://www.retrosynth.com/docs/1601/
>  I've noted that a lot of analog sequencers don't have a variable width
>clock pulse. How critical is this? I've studied the ARP 1601 intending to
>clone it (project #10 on a list of about 40), but sadly, it's been years
>since I've actually used one (and then only briefly). Is this a "top-five
>useful feature", or is simply fiddling with envelope settings enough?
>  BTW, you're lucky enough to own TWO ARP sequencers? ;) Congrats!
>
>
>Tim (but it's on the list, really!) Servo
>--
>"Imagination is more important than knowledge." - Albert Einstein

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