Posted: Wed Dec 15, 2010 6:13 pm Post subject:
Kequencer Subject description: Polyphonic chiptune generator
I had an idea the other day and I couldn’t decide if it was good or not so I just built it to find out.
Eight oscillators, an on-button and a pitch knob for each. First you adjust the pitch of each oscillator so they’re vaguely in tune with each other. Then you flick on the sequencer. Then you play polyphonic chiptunes.
So here’s what’s under the hood.
The block on the bottom left generates the clock signal that sets the tempo. C1 & R6 set the clock rate (R1 limits the maximum frequency so you can’t burn out the chip). With that clock signal being fed into the 4017, outputs Q0 to Q7 momentarily go high one after another.
The subcircuit denoted by the circle outline is repeated 8 times. It includes the indicator LED, mode switch S1, pushbutton S2, and oscillator for each of the 8 steps. The oscillator is only on so long as pin 1 is high. This high pulse can come either from the 4017 outputs, or from the pushbutton.
The outputs of all 8 oscillators are tied together via 100K resistors (R5), which is a very lofi way of keeping them buffered from each other. From there the output module is up to you. The simplest thing to do is have R7 set to about 1k – this will drive headphones directly but I can’t quite guarantee that’s a good idea. I used my rudimentary knowledge of opamps to make it more closely resemble a line-level output. In my box I also included a little amplifier module I had lying around so it makes good loud noise on its own.
Joined: Feb 02, 2010 Posts: 230 Location: California
Posted: Thu Dec 16, 2010 11:53 pm Post subject:
Fun design, and nice little tune you are playing on it there.
It is sort of a similar concept to this synth/sequencer I built:
Mine is also 4093 gatable oscillators. But I decided I wanted to be able to trigger any of the (7 in my case) oscillators on any step. I have been wanting to add some little momentary buttons like you have for "playing" the oscillators (that is what the holes on the bottom are for, still haven't added them). _________________ ∆ A. MAGIC PULSEWAVE ELECTRONICS ∆
I've tried to replicate this awesome circuit on perfboard but it got really messy and my soldier run crossed and i blew my chips
...so i decided to doodle up a pcb with Pad2Pad, a free pcb program.
the idea was for me to etch it myself, so i had to make it one sided which meant i needed to use a whole load of jumpers. its a little messy but you can figure it out.
the switch bay pads can be wired to as shown in the above diagrams, and the led bay is simple enough. connect the output bus to a jack and it's game on.
Also the 0pot, 1pot, 2pot ect will be the edge and center lugs of your potentiometers.
(i dont know how... but theres a small error on this PCB graphic on the 4093a's V+ run, which crosses several extra pins... it should be noted that this error is not on the 1:1 transfer graphic posted below)
This image has been reduced to fit the page. Click on it to enlarge.
_________________ home made noise and electronic ill-logic Last edited by stolenfat on Tue Mar 08, 2011 11:45 pm; edited 4 times in total
Joined: Mar 10, 2011 Posts: 7 Location: far far away
Posted: Thu Mar 10, 2011 10:08 am Post subject:
im in the process of building something similar
all though i might be wrong about this, i think its a better idea to leave pin 4 on 4093a and 3 and 10 on 4093b unconnected
input and output connected together on a nand gate like u have done is like an inverter witch tells its input to be high witch makes the output low witch makes the output high and so on, an oscillator
its what this circuit is all about but those oscillations isn't meant to be and will most likely just cause problems
really? well, hmm, that pcb layout i posted is still untested, in the process of gathering etching materials to see how well it works atm, but i thought one of the golden rules of lunetta was to not leave anything floating and to tie all unused pins to the ground.
rebuttal? _________________ home made noise and electronic ill-logic
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