New module, fractal gain sequencer

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, luketeaford, Joe., lisa

User avatar
Super Deluxe Wiggler
Posts: 1769
Joined: Mon Apr 05, 2010 6:49 pm
Location: Chicago

New module, fractal gain sequencer

Post by CLee » Sun Sep 15, 2013 4:46 pm

UPDATE 8.3.15
Here is a new video demo


the panel shown below is out of date and lacks newer controls

Here is some info on a new module I'm working on. I'm getting very close to a functioning circuit. I call it a Fractal Gain Sequencer (or maybe Arbitrary Wave Multiplier). It takes an input signal and steps through one of 8 pots, the higher the voltage the higher numbered the pot. The pots control the gain of a balanced modulator. 12:00 is zero gain with positive gain CW and inverting gain CCW.

With input set to INA/CV the pots will modify the waveform input to CV. Input B can be +5, set like that the output will be like a sequencer. With input B set to EXT the pots will control the gain of a second waveform, much like a ring modulator.

The Fractal control will cause the 8 pots to modify a smaller range of voltages, and the pattern of the pots will be repeated.

Here is a messy mockup of a front panel. Gate outs will go high with the corresponding pot and could be left off if you use the module as a waveshaper.


Here is a video of an early test,

The signal path (VCA and Pots) is fully analog but is controlled by a PIC chip.

I haven't tested the circuit much to see how the DC accuracy is, and still have a ways to go. But I think it's cool...
Last edited by CLee on Thu Sep 03, 2015 9:05 am, edited 3 times in total.

User avatar
Super Deluxe Wiggler
Posts: 1620
Joined: Fri Jan 22, 2010 9:03 pm
Location: melbourne

Post by diablojoy » Sun Sep 15, 2013 5:01 pm

ooh that is really cool
will be watching the development of this one
It probably wont happen today but if it does it definitely wont go smoothly.

User avatar
still learning to wiggle
Posts: 4356
Joined: Tue Aug 04, 2009 7:15 am
Location: Rotterdamm son

Post by falafelbiels » Sun Sep 15, 2013 6:30 pm

I find comfort in the fact that 4U is just eurorack sideways...
It sounds great and I want it!

Funny connectors we can work on.

User avatar
the most autistic amongst us
Posts: 6494
Joined: Wed Nov 25, 2009 9:09 pm

Post by numan7 » Sun Sep 15, 2013 6:41 pm

:party: oh how cool!

i hope i get to build one or two of these...

"the ordinary will ignore whatever they cannot explain as if nothing ever happened. and everything remains the same again..."

User avatar
Common Wiggler
Posts: 245
Joined: Thu Apr 25, 2013 2:33 am
Location: Uppsala, Sweden

Post by vurma » Mon Sep 16, 2013 1:21 am

This should be a very useful tool for messing up LFO signals. Id really like to hear the "Fractal" being CVd by a sequence.
My dystopian sci-fi webcomic

User avatar
Super Deluxe Wiggler
Posts: 1461
Joined: Fri Apr 09, 2010 5:58 pm
Location: Oly

Post by GrantB » Mon Sep 16, 2013 1:38 am

Wow more stunning original work :hail:

feedback patch?

User avatar
Super Deluxe Wiggler
Posts: 4057
Joined: Wed Apr 15, 2009 7:36 pm
Location: WA

Post by andrewF » Mon Sep 16, 2013 1:40 am

Great idea, love what it can do to the waveforms!!

User avatar
Large Member
Posts: 12061
Joined: Thu Mar 06, 2008 10:17 am
Location: Vienna, Austria

Post by Kent » Mon Sep 16, 2013 4:53 am

I want one in my Buchla. Now! :clap:

User avatar
Common Wiggler
Posts: 245
Joined: Thu Apr 25, 2013 2:33 am
Location: Uppsala, Sweden

Post by vurma » Mon Sep 16, 2013 4:58 am

GrantB wrote:Wow more stunning original work :hail:

feedback patch?
The feedback! Indeed, the feedback! Imagine what this could do as a spice to any generative patch.
My dystopian sci-fi webcomic

User avatar
Veteran Wiggler
Posts: 642
Joined: Tue Jan 18, 2011 6:30 am
Location: Sweden, bork bork bork

Post by oberkorn » Mon Sep 16, 2013 7:06 am

very original idea. so good we have seen a upsurge in interesting sequencer ideas (fonik et al), this raises the bar. please sign me up for a PCB :)
you have to pay for the music but the noise is free

User avatar
Wiggling with Experience
Posts: 412
Joined: Sun Nov 07, 2010 5:47 am
Location: Göteborg, Sweden

Post by jgb » Mon Sep 16, 2013 7:44 am

Great idea!

User avatar
Super Deluxe Wiggler
Posts: 1093
Joined: Thu Oct 08, 2009 4:19 pm
Location: Highland, IN

Post by frozenkore » Mon Sep 16, 2013 7:56 am

Sounds great and it's a really interesting idea!

User avatar
Veteran Wiggler
Posts: 597
Joined: Tue Sep 28, 2010 1:38 pm
Location: Copenhagen, Denmark

Post by mush » Mon Sep 16, 2013 11:45 am

I'd love a pcb for this one. I could see the eight "sequence" pots replaced by sliders for a euroversion though.

User avatar
demonic space drone
Posts: 2152
Joined: Mon Dec 06, 2010 5:00 pm
Location: Red Zone

Post by FetidEye » Mon Sep 16, 2013 11:57 am

i would also like a pcb!!
looks super useful

User avatar
Super Deluxe Wiggler
Posts: 1769
Joined: Mon Apr 05, 2010 6:49 pm
Location: Chicago

Post by CLee » Mon Sep 16, 2013 6:23 pm

Thanks guys. The circuit is working, now I just need to get it working well. I hope to get some more samples up soon.


User avatar
Super Deluxe Wiggler
Posts: 1131
Joined: Tue Mar 06, 2012 12:09 am
Location: Iowa

Post by lvoemachine » Mon Sep 16, 2013 6:53 pm

yeah, I'll definitely want a pcb of this as well. Looks super interesting.

User avatar
Super Deluxe Wiggler
Posts: 1708
Joined: Thu Aug 18, 2011 11:40 pm

Post by raisinbag » Mon Sep 16, 2013 9:33 pm

wow that was a super cool demo, the kids liked watching the fractal shapes on the Oscope. Hopefully I will have some bread when you release the PCB.

User avatar
Common Wiggler
Posts: 218
Joined: Sat Oct 02, 2010 7:02 am
Location: Adelaide, Australia

Post by arrmcbain » Tue Sep 17, 2013 7:04 am

That looks amazing!

User avatar
Wiggling with Experience
Posts: 388
Joined: Mon May 20, 2013 2:22 am

Post by Girts23 » Tue Sep 17, 2013 1:53 pm

Great idea! I'd be interested in PCB, as well.

User avatar
Posts: 1474
Joined: Wed Aug 13, 2008 9:15 am
Location: Finland

Post by theabsent » Tue Sep 17, 2013 2:40 pm

I want one pcb!
My releases:
My sound art & live gigs:
Modular live gigs (our modular band):
Modular Patch of The Week Channel on YouTube: ... pvEmilJScg

User avatar
Super Deluxe Wiggler
Posts: 1466
Joined: Wed May 30, 2012 11:43 am
Location: Fillory

Post by logicgate » Tue Sep 17, 2013 3:40 pm

in for a pcb :party:

User avatar
Needs more wigglin' time
Posts: 933
Joined: Thu Jul 28, 2011 7:57 am
Location: Essex. UK

Post by spotta » Tue Sep 17, 2013 4:17 pm

Now THAT's what I'm talking about!

User avatar
Veteran Wiggler
Posts: 730
Joined: Sun Jun 14, 2009 8:16 pm
Location: Portland, OR

Post by bananeurysm » Tue Sep 17, 2013 5:33 pm

I'd build one!

User avatar
Fractal Wiggler
Posts: 432
Joined: Thu Apr 08, 2010 9:33 pm
Location: Melbourne

Post by terrafractyl » Tue Sep 17, 2013 5:56 pm

I'm in for one (of course!)
'People forget that the brain is the biggest erogenous zone' -- Jackie Treehorn
Latest Album-=-Hypnagog Soundcloud-=-Kinematic Records Website

User avatar
Super Deluxe Wiggler
Posts: 1235
Joined: Sat Nov 14, 2009 7:58 pm

Post by wavehead » Tue Sep 17, 2013 7:23 pm

i want one. seems pointless in even saying it... who isn't going to want one of these?

interested to see what a smaller, non-seq panel would look like.
in buchla it should be a really nice fit.

Post Reply

Return to “Music Tech DIY”