[sdiy] 4067 for sequencer multiplexing?

[Peter Grenader]

Grant and all,

Yes, the idea of using the multiplexer to gate things through the pots other
than a contant voltage had occured to me, but  an LFO specifically had not.
Great idea.  It conjurs up Mort Subotnick and D Buchla's original concept
behind  the sequencer idea- as a method of automating tape splices.

I was originally thinking of using that z input for a simple range switch,
but...how boring is that?  Now I am thinking of a switch between a constant
voltage or an external input.  This sounds interesting.

Then there's the possibility of  reverse operation:  Using Yo - Y15 as
inputs and using  the spliced effect of them scanning to the one z output.
interesting idea indeed.

Other than that....who makes the phattest filter?

Grant:  I was on the phone with you and then suddenly I was speaking to
Debbie Dial Tone.  Called back and it was busy a few times.  No worries and
i have no idea what happened either  as I was on a land line.

best,

P







Grant Richter wrote:

> 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
>> 
>> 
>> 
>