Analog Sequencer Poll

[gstopp at fibermux.com]

     Yes more circuit boards! More more more!
     
     And now a nice interesting one to boot!
     
     >
     >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.
     
     >
     >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.
     
     >
     >3)  What kind of outboard devices do you use to control/tweak the
     >    sequencer with?
     >
     
     Or do you mean control/tweak *with* the sequencer? Or both? Well, 
     we're talking modulars here, so there is no real answer.
     
     >
     >4)  What features would you like to find on a sequencer?
     >
     
     Wow good question. See #6 below.
     
     >
     >5)  What features do you not use on your sequencer?
     >
     
     Never ask a modular user *that* question. Of course we all use all of 
     them!:)
     
     >
     >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?
     
     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 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.
     
     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....
     
     2. Don't use the 4136 quad op-amp. The pinout is weird. Use the 
     LM324 pinout, it's more standard.
     
     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...
     
     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...
     
     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
     
     p.s. I was off-line for five days, our gateway didn't just crash, it 
     shattered. While we were picking up the pieces we may have dropped 
     some emails so if anything has fallen through the cracks please 
     forgive me.