Analog Sequencer Poll

[Christopher_List at Sonymusic.Com]

  I'll be staying out of the faceplate business on this one on account of
  I've already built an analog sequencer (with faceplate!) - though I may
  wind up ordering a circuit board, as mine is a mess of enhances all
  squished onto two protoboards.
  Because my sequencer is very similar to the Superseque I figured I'd add
  some comments.

  1. My sequencer was 2x16. I wanted more rows, so I added a "piggyback" of
  3 rows - with no clock stuff, just driven from the same data lines as the
  main unit - with 3 rows of knobs. I realized later that it would have
  been much more useful to have it switchable between 2x16 and 4x8 - just
  put some output jacks in the middle of the row, and drive the columns
  with two 1x8 muxes rather than a single 1x16 mux. It would require some
  CMOS switches to stop columns 1to 8 from getting summed with columns 9 -
  16, but 4053s, 4016s - they're cheap and simple. Anyway the reason for
  this is that the circuit (and board) is relatively simple (hell I did it
  on protoboard with a made from scratch flash A/D cobnverter built in!)
  the hard part - the nightmarishly tedious part - is wiring up and
  screwing in place all of those friggin' pots! If you can switch it then
  the pots can do double duty...

  2. Superseque has buffers for each column voltage - I didn't need to do
  this (but, it's a lot easier when you're using a PCB rather than
  protoboard to add the extra ICs). I used two CD4069 muxes - one to drive
  the pots, one for the LEDs and drum-trigger switches. I connected the
  input pins to +15v, and the output pins to the pot columns or the LEDs.
  The pots are 100K, the resistors from the wipers to the summing amps for
  the rows are 220K - I've had no problems...

  3. What about switchable output 0 to 5v or -5 to +5. I've found this
  useful, but if you do what I described in #1, it'd be tough to find a
  place for the switches! It's nice when you're stepping at audio frequency
  to get +/- waveforrms, but for regual control of pitch and stuff a 10v
  range is a little much...

  4. The CV control of step is something I put in my sequencer that I
  hardly use. It's easy with something like the CD4516 that has those "jam
  inputs". If I were to do it again, I'd definitely use something like an
  ADCxxxx parallel A/D IC rather than build one up from hand with
  comparators. Even though I don't use it much - I still think it's a cool
  feature - any PCB made should have a counter that allows for this and
  should be set up to allow for hacking so that something like this could
  be added...

  5. If it uses anything other than +/-15v I would hope it has a voltage
  regulator built in :).

  - Just my thoughts...

  - CList