Fenix IV

Published by Priscilla Haring-Kuipers on

Right now we are at the point where we can do our first experiments. We have gone through most of the original design schematics, we have ideas and we have some of these ideas figured out in new schematics that we can test in physical form. Although everything is open to change – because we build, test, learn and possibly change our mind along the way – we are getting to know our Fenix.

Fenix IV experiment board no 1

Overall we are using a lot of the Fenix II signature sound from the oscillators, filters and weird envelopes. We want to keep the design philosophy of grouping the knobs and the jacks separately. The Fenix has a set of eclectic building blocks that are all different while keeping a different kind of internal consistency: It is all connected. Meaning that if something has three outputs, there is always a way to combine these three back together. Everything has somewhere to go. This essence we want to keep and where possibly, digitally improve it.

Using schematics of Fenix II they first needed to be ‘modernized’. Electronic components and means of manufacturing have changed quite a bit since the Fenix II was released. Some of its’ original parts are not available anymore and/or not ROHS.

Inside Fenix IV (under development)

  • A new three-band Formant filter – based on a little bit of Fenix II and a lot of OTA filter, the schematics are mostly homemade and this filter is on our Experiment Board 1. This is also one of the filters in our Big Fish development.
  • Three separate filters – a ladder filter, a low-pass gate and a state-variable filter that are all taken from the Fenix II schematics and modernized. The low-pass filter is on Experiment Board 1, the ladder we are still fiddling with and the one-state needs a complete overhaul that might involve Curtis chips…
  • Four LFOs – one based on our Wobbler, three analogue LFOs based on Fenix II modernized schematics and maybe another digital lfo but we are still discussing this.
  • Tuned delay with four delay lines – mostly dsp code from earlier plugins we’ve made, here we use physical modelling and we are in the design phase of selecting the proper mcu and memory combination.
  • Phaser – using the modernized Fenix II schematics with a slight change in the feedback path, design is done and will be on the second Experiment Board.
  • Wave multiplier and Wave shaper– so far we’ve modernized the Fenix II schematics but we expect to change a few things once we can play with it on the second Experiment board.
  • Envelopes – we are aiming at three envelopes, they might all be based on the core of the three envelopes in Fenix II, or based on the Curtis chip envelope in our RectangularThing. Both these envelopes are on Experiment Board 1 so we can play with them and discuss further. We are also eyeing our Edgecutter envelope.
  • Sample-and-hold – we expect the Fenix II schematics to have issues with components and modernizing will be a challenge
  • Rectifier – modernized Fenix II version, no problem
  • Mixers – probably six mixers in Ardabil style (on of our other modules under development) since we wont assume stackable cables there will be multiples and the mixers will have more of a utility function combining VCA and mixers
  • Sequencer – yes there will be one, beyond that there is nothing certain yet
  • Ring modulator – we have a Fenix II based version on our Experiment Board 1 that we want to test against other Ring Modulators we already have that are based on modern chips
  • Noise source – we want to spend some time reinventing the noise, this may become a analogue/digital hybrid thing, we have some ideas and much to do here
  • Display for system settings and use as an oscilloscope – all homemade schematics, the design is done and will go on the second Experiment Board.
  • LEDs for visual feedback – concept from Wobbler, we want to see how this applies to different things as a UI, is on Experiment Board 1.
  • USB and MIDI connection for CV and gate out – probably four of them. Based on an already running design that we have made.

Experiment Board 1 front and back

Our Fenix IV will be setup in skiff style – which means that we load all the hardware on pcbs that are parallel to the frontpanel and not at a 90 degree angle like the original Fenixes. This also means that we have to populate our PCBs on both sides (unlike our modules which are populated on one side) because this beast has a lot of parts. We plan to give our Fenix a pcb-shield behind the populated PCBs and hope to give the whole thing a 6cm depth, including power supply. Skinny Fenix.

The parts of our Experiment Board 1 have arrived today– we have the PCB and we have all 1202 parts. Now we just have to solder all the things.

Please follow us online to keep updated – see what survives experimentation and what doesn’t and what other flashes of insight might occur while playing with the parts of our Fenix iV. A visual of the progress – with loads of pictures of design files – here 

In order to do all of this we have also designed another part of our software toolchain that allows us to collaborate on big board designs such as this one, as well as a soldering tool. Perhaps more on this in the next blog.


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