K4815 Pattern Generator

[elmood]

Hey folks,

I've been building modular synth stuff for fun since the fall, and so far it's been an incredible experience. You can read about it here:

http://www.andrewkilpatrick.org/blog/?page_id=1136

Anyway, I'm working on my first commercial synth module (I sell other music electronics already) designed for the eurorack format. I have questions for folks in the USA or Canada as to where to buy eurorack hardware (rails, enclosures, etc.) but in the meantime I thought I'd share a little bit of what I'm working on for my first module.

It's called the K4815 Pattern Generator and is an expanded version of a little MIDI gizmo I built a few months ago. The idea is to create various rhythmic and note patterns for either jamming or just coming up with new melodies in a semi-algorithmic way. The user is still in control, but it's easy to have unexpected music come out.

Here's a short video of my prototype... not all the functions are done yet, but you should get the idea:

http://www.youtube.com/watch?v=PQuSZAsuWAQ

A few of the controls don't work yet. The basic connections are:

- clock input
- reset input (starts the pattern from the first step)
- direction input (reverse direction under voltage control)
- CV / X out - 12 bit analog voltage
- gate / Y out - 12 bit analog voltage

The CV and gate work as normal for note mode, but in X/Y mode you can create modulation/panning signals instead of notes which I think will be quite interesting for lots of uses. Basically the motion creates a 2D output which should totally cool for people who play around with quad channel sound.

There will be MIDI available internally, and I hope to make some sort of adapter so you can use it with MIDI equipment also.

Anyway, it's coming along but I'd love to hear your comments. I think the price will be quite low, and I might offer a kit (although there are some SMT parts)... I haven't worked out that part yet.

Thanks for reading (and watching) and I look forward to your feedback!

[davep]

Nice! This looks like a really interesting module. A few ideas -

If it's not a big hassle, provide modulation inputs for some controls so you can do things like change patterns or note density under CV control.

I recommend designing the PCB with power connectors (and appropriate DC input power compatability, 12V versus 15V etc.) for all the major formats - Euro/Doepfer, MOTM, and Dotcom. That way, you have a wider customer pool just by changing the front panel & jack size.

[Rykhaard]

Firstly - welcome to electro-music! When I'd first read a message from you, seeing Toronto, I went to your webpage to read; reading more and more and ... but afore I babble on endlessly ...

That is a wild idea for playing notes; controlling functions; etc! The few things that you were able to display so far, was absutively phenomenal in potential! I can't wait to see more of it.

Now - as to what notes when / where, that IS a major question from me.
A set of questions, more'n likely ...

Are the notes chooseable for playing, going to be in repeating patterns through the XY matrix, or can individual notes within a sequence be told not to play, or, individual notes sustained?

Would there be possibilities of different functions for certain notes? (Alternate velocities / other functions.)

I could ask a bunch more but, maybe it's best to see where you're intending to go with it.

To try and cut my babbling short - the initial excitement were seeing another builder in Ontario! (I'm in Kitchener.) In my 5+ years living here, I've only met 1 other (from Toronto) very briefly a couple of years ago, when he popped down to pick up all of my Electronotes back issues, as well as some single sided blank PCBs. I'm not even sure if the chap is still on this forum. (Colin something, if I recall correct.)

I'm also very curious about the sequencer as well as PICs themselves. I've debated a couple of times jumping into the PIC world, but seeing the length of chips available from the sources ... where to start.

And finally, I've been designing / building my own 1V/octave sequencer since 2008. The 4 step note sequencers are currently working. I'm just now working on their controller.

K. I'm rambling ... there're a couple of vids of my sequencer development and a few other things at my youtube site, in my signature.

Looking forward to what's coming from you!

[elmood]

Thanks for welcoming me! I've been poking around here for some time but want to get more involved in the discussion. There seem to be so many great people here... I wanted to check out the conference in October but I didn't have time in my schedule to take the trip to NY.

Rykhaar: To answer some of your questions...

As for where the notes are and how to play them... The notes are fixed on the grid. You can choose the tonality (either major or minor so far) and also the size of the scale. I haven't completely figured this out yet but I think it will be something like 2 or 4 octaves. The "sequencing" happens not by stepping through the points on the grid sequentially (you will just hear an ascending major or minor scale) but by jumping around in different patterns.

The main idea is to supply a number of different patterns with different "motions" around the grid. My current design has something like 32 patterns which can be each up to 64 steps long. Each step can go to any point on the 8x8 grid. The idea is to choose a scale size, tonality and pattern that gives you the notes that you want. You can also set the pattern length if you don't want to hear all 64 steps.

But obviously playing a note for each step is kind of boring, so then I have this idea of the "density" parameter. This draws patterns on the grid (in a dimmer shade of light) that are the "enabled" notes. If you turn it all the way up all the notes play. If you turn it down you get various density patterns on the display. When the "ball" (which I'm calling the playback position) lands on a dot that's lit, the note for that position will play, otherwise it won't.

Alternate velocities... that's something I haven't thought of. Currently there is a gate-time pot... I have it set up so that notes can be longer than 1 step, so if you have spaces, the notes can keep playing beyond the end of the step. I suppose I could make a way to make different note playback parameters too... hmmm....

Another major concept (which isn't in the video) is using the outputs for X/Y control instead of notes. The idea here is that the ball position on the grid produces an X/Y output instead of CV/gate based on its position. If you use the note density this can affect when the outputs get updated. So you can create different modulation rhythms... would be cool for filter cutoff I think.

One other thing I'm really trying to delve into is bringing more MIDI capability to the modular synth world. Most of my time making music stuff before I started my DIY modular was with MIDI so I kind of felt relieved by the simplicity and also somewhat lost when all I could use was analog voltages. The certainly lack some important things that MIDI offers.

The front of the panel has inputs for clock, (TTL style) a direction input (which reverses whatever you have set on the switch already) and a reset input which starts the pattern from the first step. But inside the module there is a little header with MIDI on it. I intend to make some breakout modules to offer more functions through this interface. This include MIDI clock I/O as well as the ability to shift the base note for the sequence from a MIDI note... so you can groove in different keys easily. It's also going to send controller changes in X/Y mode, and I suppose it could accept controller also to affect parameters in realtime. Doing all the main panel I fear would make it too big and expensive.

Unlike most modular sequencers, mine treats the clock specially. Instead of just advancing to the next step on each clock pulse, it actually recovers 24 pulses per clock signal internally. This comes out the MIDI output as a MIDI clock signal, so you can use this module to derive MIDI clock from a 1 pulse per beat input. But... you can also change how often the pattern steps, from 1 to 24 steps per beat. So if you already have some other module running at some rate, you can have this one use the same clock to run at some different rate. I have a feeling this would be very useful for a lot of people. At 1 step per clock it works just as a normal sequencer. But unfortunately because it multiplies the clock internally, it can't follow varying clock signals at anything but 1 step per clock. (because of course it doesn't know where the next beat will be)

Anyway, the clock recovery/multiplier part and MIDI / TTL clock converter is something I think might be cool as a dedicated module. It's something I developed for another project which takes audio click tracks and interpolates the beat for displaying on some LEDs. Now I see in the synth world there is a lot of uses for this kind of thing.

Lots more to discuss I'm sure... btw if you want to get into PICs, I can help you select some... I know there are so many to choose from sometimes it makes my head spin. But there are some good ones which I keep coming back to... I can help you get started if you want.

[Rykhaard]

[emdot_ambient]

Very awesome module, I have a total fetish for sequencers...but right now I only do 5U DIY stuff ;(

[a100user]

This is so cool. I just watched the second demo video, wonderful stuff.

It would be very cool if those controls were CV-able too

Look forward to a commercial release. Any thoughts on timescales and price yet?

David

[elmood]

Hi folks,

Sorry for the long absence... I've been hard at work building stuff.

Anyway, the K4815 Pattern Generator is finally ready and the first units are shipping hopefully this week. I have a small number of units left for direct sale, and would love to sell out this first batch of units.

I haven't had a chance to make any new videos, but the manual is online for those of you who like to dig into the nitty gritty.

http://www.kilpatrickaudio.com/?p=K4815


Thanks!