"Betsy - Sequencer(Top)"
It looks a little better than it is, because I still haven't finished it :). The row of switches and the row of buttons aren't connected, but everything else is.
I came up with the design for this sequencer based on suggestions from synth-diy mailing list members, and by studying CMOS 4000 series data sheets to find what I needed. It's very similar to both the design for Thomas Henry's Superseque sequencer, as well as the Serge TKB sequencer. I'm afraid I don't have any schems for it - I kind of made it up as I went along. It's driven by a 4516B counter and pair of 4069B multiplexes. The input of the multiplexes is +15v, each output of one of the plexers goes to a column of pots in the top half of the sequencer, each output from the other goes to a row of pots, an LED, and a gate jack on the bottom half.
The Knobs - There are 5 rows of 16 knobs. Each row has it's own output, and each output has a switch to determine whether the scale for that row will be 0v to +5v or -5v to +5v. There is also a "A - B" output that gives the difference between the 4th and 5th rows.
The Switches (not yet implemented) - these will work like a drum machine. The "C" output will be high when the sequencer is at a step where the switch is high. The circuitry is simple, but I haven't felt like doing all the wiring - the knobs were bad enough!
Gate Outputs - The row of green jacks in the middle are gate outputs. +5v will be output from the jack when the sequencer is on the jack's step. I mainly use this for resetting after a certain number of steps. The gate output on the far right is high as long as the clock pulse is not firing.
The Buttons (not yet implemented) - The plan for the buttons is that pressing them will cause the sequencer to jump to a given step (by setting the "jam" inputs of the counter IC driving the thing). Again, the wiring is a drag.
The Clock - the sequencer has no internal clock and must be run from an external signal. I often run it from an audio VCO. It steps when the input voltages crosses 2.5v in the + direction.
Manual Advance Switch - The sequencer can also be advanced one step with this momentary contact switch.
Program Select Input - This input sets the current step of the sequencer based on the input voltage. With an input voltage of 0v, it has no effect. With an input between .31v and .62v, the sequencer will stay locked on step 1, between .62v and .93v it will lock on step 2, etc. When the input voltage is 5v or more, it will lock the sequencer to step 16. The input is full wave rectified so negative voltage work the same way. I built this feature by building a flash A/D converter from comparators and encoders. The output of the encoders goes into jam inputs of the counter. The A/D converter is not as fast as I'd like it to be - I may switch to a monolithic IC 8bit converter.
Up/Down Input and Switch - This switch sets whether the sequencer steps up or down. The input jack is a voltage controlled override - if a cable is plugged in here and the cable is below 2.5v, the sequencer will step down, above 2.5v and it will step up.
Hold Input - Input jack allows voltage controlled "hold" function - if the signal going into here's below 2.5v, the sequencer will work normally, above 2.5v and it will not be able step from the clock input.
Reset Input - Input jack allows the sequencer to be reset to step one. Used in conjunction with the gate output row, the sequencer can be set to cycle through any number of steps from 1 to 16. For an 8-step sequencer you patch gate output #9 to the reset.
Copyright 1998, C.G. List