[sdiy] Suitcase synth - analog switches

[Tim Parkhurst]

Hello Again,

Another way to implement the analog switch might be to use a LM3914 bar
graph driver. Adjust the range and offset of the input waveform so that only
the first four outputs come on (it has ten output lines) and use those
outputs to drive analog switches. The nice thing about this approach is that
the voltage select function is built in. You could sequentially select the
outputs by driving it with a saw wave (up or down depending on the polarity
of the saw). The 3914 can also be set so that only the highest output comes
on ("Dot" mode), or that the highest and all outputs below come on ("Bar"
mode). It's a very fun chip. Check out Grant Richter's "Analog Tracking
Generator" for a very cool application of the 3914 for some more ideas.

http://www.musicsynthesizer.com/DIY/Grant/grant_richters_synthdiy.htm

Tim Servo

"Imagination is more important than knowledge." Albert Einstien
******************************************************
> -----Original Message-----
> From: Electronium [mailto:mike at electronium.com]
> Sent: Wednesday, January 08, 2003 8:46 AM
> To: Tim Parkhurst; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Suitcase synth - analog switches
> 
> Hey Tim,
> Great idea!  Do you know of any example schems I can look at for something
> like this?
> 
> Something a little different than what you're talking about, but the
> current
> sequencer design incorporates a 2x1 switch that switches between channel A
> &
> B and creates a center channel (A/B).  When you have both channels set to
> a
> sequence of 8 steps, this creates a 16 step sequence on the 3rd channel,
> since it switches on the reset pulse of either of the two 4017 counters.
> But when you set the two sequences to anything other than equal lengths,
> you
> get all sorts of pseudo-random patterns.  Hopefully, I'll get the
> schematic
> sorted out & post it soon...
> 
> Best regards,
> Mike
> mike at electronium.com
> 
> Tim wrote:
> 
> 
> > Looks great! I love the simplicity of it. One of the few things I might
> add
> > would be some analog switches. Maybe a clocked 4 in - 1 out, kinda like
> a
> 4
> > position analog seq. Or perhaps even have voltage control of the
> selected
> > output. I remember getting a lot of use out of the analog switch on an
> ARP
> > 2600, and that was only a 2 in - 1 out.
> >
> > Tim Servo




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