Analog Sequencer Poll

[Tony Clark]

   I've been replying to most people privately, but since Gene was so 
good to write such a long post, I'll be kind and share my insights with 
everyone as well.  LONG POST!

>      >1)  What are your preferred number of stages (1x16, 2x8, etc)?
>      >
>      
>      I like the 16x2 idea as a minimum. Of course if you drive the pot 
>      columns hard and load the pot wipers lightly the only limit to the 
>      number of rows is your panel space and pot budget.

   Erm, 16x2?  What are we, Chopin?  :)  Anyway, it looks like I'll be 
settled on doing 3X16.  I was going to do 4x16, but the way I'm doing the 
board layout lended itself to this configuration more naturally.

>      >2)  How fast should a sequencer be able to cycle through its stages?
>      >
>      
>      Audio rate. If the range of the VC clock is a concern, add an external 
>      clock option as well as internal (besides external clocking is 
>      important for other stuff like syncing). Sequencers generally are 
>      based around CMOS or TTL circuits and so will naturally go way above 
>      audio just because of the speed of the logic chips.

   I've only had ONE person define what they though the upper limit would 
be in HERTZ.  Audio range doesn't cut it for me as that is a fairly large 
range!  I was given 500Hz, but audio range could be well above 10kHz!  
Remember to help me out a little.  I've never owned an analog sequencer.  
;)

>      >6)  Add additional comments...
>      
>      This is a complex issue - do we want to include the features that 
>      already exist on analog sequencers, or do we dream up features that 
>      don't exist on any sequencers? Maybe we should just think up as many 
>      as we can and see if they can be fit in?

   Well it's not just a matter of using what exists or doesn't exist, but 
rather what FITS the sequencer the most naturally.  Here is a list of 
some things that people have said would be "good features":

   CV->clock speed
   CV->gate length
   multiple CV in
   CV in scaling
   CV out scaling
   voltage inverted CV outs
   quantized outputs
   multiple CV out busses assignable per row and stage
   individual gate out per stage
   gateable start/stop/reset
   DIN sync
   variable gate timing
   single step
   manual reset
   individual clock divide per row
   pulse width modulated clock source
   onboard LFO
   clock ins and outs
   lag processors, output/stage
   up/down-up-down-random pattern modes
   loopable different length sequences
   note skip

   I apologize if some of these might repeat themselves.  Now some of 
these things are already implemented into the Superseque design.  MOST of 
them are not.  I have no problem in adding stuff and tinkering with the 
design.  I don't think there is any reason that I or any of us have to 
stick adamantly to any one person's design.  In fact, I've already begun 
doing some major redesigns to the superseque.
   For starters, I've thrown out all the CMOS counting circuitry.  I want 
to be able to divide my row stages up.  So instead of just having the 
standard 1x16 pattern, I'll be able to get 2x8 and 4x4.  Sorry Gene, no 
16x2's...
   Now one person I've heard from already doesn't like sequences smaller 
than 16.  Well, you don't have to use the feature if you don't want to.  
My way of designing circuitry is to give you the ability to utilize the 
device to the maximum.  It's my way of minimizing the number of times you 
say to yourself "Gee it would've been nice if it did or had this..."
   Some of the suggestions are fairly simple things to add.  Just little 
enhancements of what's already there.  Those things I think will benefit 
all of us.
   Some of the suggestions are asking for a little much.  Anything that 
deals with having two or more completely independent rows.  What this is 
called is "the desire to have a second sequencer".  That's because I'd 
have to put literally the same circuitry in there twice.  Now once I get 
the board designed, anyone is more than welcome to stack 2, 4, 16 boards 
in a rack unit and have as many individual rows as they can handle.
   What I'm simply trying to avoid is a super colossal circuit.  IF I 
want to keep the board to the same size as the ASM-1 board, THIS is going 
to prove a challenge and a half.  There are a heck of a lot of ICs in a 
16-stage sequencer!  And the more options you try to get me to implement 
means the denser the board gets.
   So let me put a couple of options in front of you:

   We can have a super loaded sequencer with all the options you can 
convince me to put in it.  I'll either have to use SMT (surface mount 
technology) or go to a double board configuration.  If I go the SMT route 
(which doesn't bother me in the least), I doubt many of you will find the 
task of assembling one of these boards any fun!
   Or, we can have a simpler, well thought out sequencer with enough 
options to keep most everyone happy.  I'll only use thruhole technology 
(which is what I'm trying to maintain) which will make it easier for most 
anyone to assemble.
   OR, we can screw the board size and go to something bigger.  We can 
add more options and still maintain a degree of simplicity in board 
construction.  Again, I'm not picky, I just thought that Gene's board 
was a nice portable size.
   So there you have it.  I'm going to be interested in hearing responses 
to this post!  Now is a good time to get your suggestions in to me as to 
what you'd think would be good features.  I've just about finished doing 
the logic work on the row splitting function and next I'll be attacking 
the master clock/counting circuits.
   I had to do away with all the CMOS 
circuitry due to the fact that there just isn't the variety in ICs 
unlike the TTL series.  Actually I'll be mixing the two kinds together to 
achieve the same level of compatibility.

>      Ric Miller's mention of Tangerine Dream brings up such a point. In 
>      much of their live (improvised, I think) music, you can hear the 
>      sequencers being tweaked. From observing them I think I figured out 
>      their schtick - Edgar did the melodies and themes, Chris dinked with 
>      a bunch of sync'd Moog 960's, and Peter goofed around with the drum 
>      triggers. Chris' job was to establish the bass lines and sequenced 
>      melodies, and it sounds like he used the "STOP/STEP/SKIP" switches 
>      on the Moog 960 a lot, in real time.
>      
>      Now these switches alter the length of the sequence. In fact, there 
>      is no "master step length" selector on the 960 - if you want less 
>      than 8 steps you must set one or more columns to "SKIP".

   I'd be willing to try for variable length per stage with a skip 
function.  Stops are a definate part of the musical score, I can't quite 
imagine a sequencer without them.

>      I think the Roland System 700 had the capability of setting note 
>      length per step with a rotary switch. The Emu modular sequencer had 
>      the pot panel split off from the step counter, so you could patch up 
>      the binary address lines in strange ways to make the pot steps jump 
>      all over the place.
>      
>      However despite all this it may be that we want to stay close to the 
>      Superseque design, and just spice that up with whatever is easily 
>      added. From the looks of it there's enough basic functionality in 
>      the Superseque to justify using it as-is.

   By the looks of things, I don't think the end product is going to BE a 
superseque at all!  It's going to be something that only us analog 
fanatics could have dreamed up!

>      Things I'd do different from the Superseque schematic:
>      
>      1. Bring the CARRY IN and CARRY OUT pins to the panel. The IN can be 
>      used to halt the counter (freeze it in the middle of the count, 
>      etc.) and the OUT can be used, aw heck somebody will think of 
>      something....

   The carrys could be used to string two or more sequencers together.  
You could get a 1x32 or 1x48 out of it if you plan it right.

>      2. Don't use the 4136 quad op-amp. The pinout is weird. Use the 
>      LM324 pinout, it's more standard.

   Actually, the pinout isn't as strange as you may think.  I thought it 
wierd when I first saw it, but if you look at it, the bottom part of it 
has the same pinout as standard 8-pin dual op-amp IC.  Then add two more 
op-amps to the "front-end" and voila.
   I do agree with using more standard ICs though.

>      3. The 33k/4k7 reference voltages at each op-amp are redundant. You 
>      can use one reference for all four places. Add a big cap here too.
>      
>      4. Put a bypass switch around the cap in the RESET input line. This 
>      will allow you to choose whether the RESET input will reset the 
>      counter on an edge, or hold the counter in a reset state with a 
>      level.
>      
>      Do we want to include the count clock on the PCB? Probably at least 
>      something simple, for those times when an external clock isn't 
>      needed. We do probably want a latched STOP/RUN thing on the front 
>      end...

   Yep.  All noted.

>      How about a row of trigger switches, so you can select 1/16 notes 
>      like on a TR-606 in write mode? Just for grins, probably easy to 
>      do...

   I was thinking about a row of buttons across the bottom that you could 
trigger each stage with.  This'd be handy for tuning and calibrating each 
stage without having to do tons of loops.  Or are you talking about 
something different?

>      Also keep in mind - once we have the circuit board, we STILL need a 
>      front panel! And for sequencers, that's a lot of hard work! (Uh, 
>      Chris, you listening?:)
>      
>      - Gene
>      gstopp at fibermux.com

   Lots of work all around.  :)  Good thing I am on good terms with my 
employer!

   Tony

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I can't drive (my Moog) 55!
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Tony Clark -- clark at andrews.edu 
http://www.andrews.edu/~clark
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