[sdiy] 4067 for sequencer multiplexing?

[Grant Richter]

Hi Peter,

Say, your cell phone disconnected the last time we spoke, the line went
dead?

Using a voltage multiplexer for voltage sequences has some advantages.

In the 4017 style sequencer, you sum together a bunch of pots with an
op-amp, then only supply voltage to one pot at a time. Since the others are
at zero, only the active stage contributes to the output. Diodes can also be
used, but they have a temperature coefficient and a 600 mv. drop. The 4700
PAIA sequencer used this method.

Using a voltage multiplexer allows you to switch in other things than the
pot. For example, take the pot wiper to a switchable jack, then to the
multiplexer. Now you can insert an LFO or other voltage source for that
stage. It's interesting to make a sequence spliced out of pieces of other
sequences.

If you power the CMOS switches from +/- 7.5 volts, and use an attenuator of
0.5 on the input, and a gain stage of 2 on the multiplexer output, then the
switches will only see 5 volts internally for a 10 volt through signal.

Now you could use the device to splice audio (+/- 5 volt) sources.

Did you ever read "The Ticket that Exploded" by W.S.Burroughs? The premise
of the book is that splicing audio sources at 24 Hz causes a brain virus.
Luckily, skepticism is anti-virus software for the brain.

> From: Peter Grenader <petergrenader at mksound.com>
> Date: Thu, 10 Oct 2002 19:11:11 -0600
> To: synth diy <synth-diy at dropmix.xs4all.nl>
> Subject: [sdiy] 4067 for sequencer multiplexing?
> 
> Have any of you guys (and gal) ever considered using or used a 4067 for a 16
> step sequencer?  It's an interesting little bug as it is actually a bank of
> analog switches which are addressed by 4 bit data with a common
> input/output.
> 
> So, you want to pass a low out as true, you ground the common.  You want a
> high, you connect a high at the common.  In that this project I'm cooking up
> is going to be gargantuan, I'm going to use line drivers after to boost the
> umph for 4 banks, a pulse out, a programmable pulse out AND an LED per tap,
> so I'm not all that concerned with it's internal strength as there will be
> no fan outs.
> 
> any info would be terrific.
> 
> thanks,
> 
> P
> 
> 
>