Shell Waveshaper PCB+Panel released <- fricko

[Ricko]

Happy to announce the release of the Shell waveshaper as a PCB/Panel combination for Eurorack DIY, on my fricko.home.blog website. I think it a great waveshaper for getting variations of the lowest four or five harmonics, but it produces medium and high harmonics too.

This is a version of my Fibonacci waveshaper design I put up a couple of years ago on Muff's (https://www.muffwiggler.com/forum/topic-179588.html). I found a picture of a waveshape in some academic material that just had harmonics of the Fibonacci sequence (1,2,3,5,8,13,21 etc) and I tried to figure out a circuit to approximate it: it had a regular shape but not one that was possible to do with conventional waveshapes from VCOs. The module makes a family of sounds based on three segments of differing widths that can be tilted or blanked in various ways.

Readers interested in the technical details of the waveshaper may like to read the "backstory" page on that site. Shell = Fibonacci geddit?

The current board is non-ROHS, but I have ROHS boards on order now, for EU and UK people. It is 4HP but a 6HP panel is on order, due late next week.

Attached is an audio sample: three tracks of drifty saw VCOs through the waveshaper: no filters or effects were used, all variation is the waveshapers and the drift-chorus. At the end you can hear the chuffing sound that the modulation input causes.

---

ShellDrone.wav
Description:	Drone made with three tracks of Shell waveshapers, going through the various sounds of the waveshaper in rough sync. The input is a saw. At the end you can hear some LFO modulation.	Download
Filename:	ShellDrone.wav
Filesize:	10.32 MB
Downloaded:	825 Time(s)

---

[Sven]

Where can I find the schematic for the module?

[Ricko]

If you go to the link on the MuffWiggler site I gave above, the basic Fibonacci circuit is there. That is the core of the Fricko Shell module. (You can also be amused/appalled by my dummy spit about people who cannot read my mind! Soooo embarrassing. )

It is public domain, so anyone is free to use the idea or copy that diagram without license or attribution etc. It is just a frequency doubler, a window comparator, and a blanking transistor. VCO designers, for example, are free to add it as a waveshaper without attribution if they like (they probably already have the square and saw, so an in-VCO version could be much simpler, minimally just a summer and the window comparator set to 1/3 or 1/5 with a feed from the PWM socket to a threshold, plus a blanking trannie!)

Most of the Fricko modules will be tidied-up and value-added versions of designs I have put up public domain over the last decade or so.

The Fricko Shell PCB also derives another waveshape for the blanked section and allows mixing between the Fibonacci-style shape and that ("Tilt"), and a non-dramatic modulation input for one of the window comparator thresholds. Customers get the full schematic on purchase. (Most Fricko boards have test points and these may be useful for hacking too.)

Regards
Rick

(B.t.w.: The ROHS lead-free boards are now 85% manufactured, the fab plant informs me with improbably precision, so I expect they will be available later next week for EU and UK builders or on request. The 6 HP panel option will be coming in the same delivery, for musicians who prefer that.)

[Ayab]

Great sample Ricko it has a really supersaw like quality to it.

Glad to see a modular designer pushing the possibilities forward!

I'm looking forward to the pcbs and panels for Europe being ready for you to ship.

And your generosity with your designs for the good of the synth making community is awesome