[sdiy] it's SEQUENCER time!!!!

[Peter Grenader]

Lady and Gents,

I had a frigging' a-piff-a-me last night and its going to manifest itself
into yet another sequencer. This one's gonna be a big'gun - 3 banks of 16
with pulse outs for each step, a set of switches for programmable pulse
patterns, and full vc of direction via an external voltage,  a keypad and
pulse inputs  for immediate step assignment.

Ouside of Grant Richter, every manufacturer (I am aware of) currently in the
mod game has overlooked what I feel is an essential function of sequencers
first intoduced by the grand daddy of sequencers himself - Donny Buchla:
the ability for an external voltage to override the count and step location
and assign (voltage control) the manner of travel.

Some, like the Modcan and Serge TBK do random (quasi), some do pendulum and
reverse, but only Wiard allows to you control the direction with an external
voltage.  Analogue Solutions came close, but IMHO fumbled on the one yard
line by bringing the 4 preset inputs of the master clock to the faceplate,
yet has no gear available to create four bit binary data, so it's kind of a
wash.  Grant explained to me once (it's on his personal sight, too) how he
plops in this control via XOR gates. I've spent the last two days trying to
figure out the truth tables behind this and I cay-n't.  So, I've figured out
another way of doing it:

An external voltage going into a ganged set of 3914s acting as a 3 bit A to
D.  Sixteen outs from that going through 16 PNPs to create full range
high-true signals. Feed those into a 74510, where the serial data is
converted 4 bit binary, those four bits fed into a CMOS latch, the output of
those going into the preset inputs of the master binary clock.  It's a snap.
Strobe the latch with the same pulse that's driving the master clock.  The
preset inputs can be enabled by a comparitor that senses anything higher
than ground into the external vc input.

The way it works is straight forward.  For dicussion sake, let's say the
maximum voltage level will be eight volts.  Having that at the vc input will
send a a high out of the sixteenth PNP, with the 74150 will read as 1111 and
preset the master clock to step 16.  Four volts into the VC will create a
0001 and send the sequencer to step 8, and any permutation inbetween will
send the sequencer to it's associated output.  Remember, the two 3914s
create a 3 bit binary A to D and will create 16 equal divisions of the full
input range.

Further thought led me to the idea of incorporating 16 touch plates to step
assignment (a second 74150 would be the easiest way to do this) which could
also be multed to 16 pulse inputs so a gate signal would do the same as the
pressing a key.

it's a grand undertaking, but a bit easier for me in that I've already made
the ganged 3914 engine which already includes the PNPs on the outputs.
There are a couple of other features I'm thinking about that will involve
using the outs of this to create midi note-on messages that I will get to in
another post.  I've happened upon 3 pot PCBAs for a very fair price from a
Doepfer 116/3 so I won't have to worry about wiring 64 pots, which would
drive me nuts.  Each board comes with 16 pots and sixteen leds.  One bank of
leds will be used for just that.  One ill be used for the stage pulse
outputs,  one will be fed through swtiches which will allow for programmable
pulse patterns.

So, in the coming weeks I will begin this undertakng and will give
information of pitfalls I will undoubtably fall into as they occur.

Anyone else think of doing this ever?

let me know and thanks,

P