Fehler Fabrik V2 modules released

Hello all, I’m very pleased to announce the release of my set of VCV modules on the official library.

These modules were made originally as programming exercises, but over the course of their development a few people seemed to enjoy using them, so hopefully more people can enjoy them now. I’m a self-taught hobbyist when it comes to programming, so please let me know if there’s any issues or bugs that arise during usage, ideally over at the Github page.


Arpanet is an attempt to recreate the ARP Instruments 1601 step sequencer. Reading the manual for the original is the best way to learn how to use Arpanet.


Aspect is a basic clock divider and sequential gate sequencer. The left set of outputs are divisions of the input clock, and the right set are the sequence output. Gate highs are 10V, lows are 0v.


Chi is a three band polyphonic crossover, like those found in high-end DJ mixers and PA/HiFi system controllers. It uses 4th order Linkwitz-Riley filters to ensure flat and coherent recombination of audio bands. Two frequency cutoff controls determine where the low/mid (80Hz - 640Hz) and mid/high (1kHz - 8kHz) filter bands meet. Each band has it’s own output with (voltage controlled) gain control (-inf dB through +6 dB), which can be used as feeds for multi-band processing, and a master output which recombines all bands - like a DJ mixers Isolator section.

While Chi can work polyphonically, it’s currently not very well optimised - I still need to figure out how to utilise SIMD for this kind of thing!


Fax is a sampling sequencer that will produce a crude facsimile of a recorded input. If no input is present it will record the movement of it’s big central knob. The transport controls are similar to Arpanet’s.

When recording is active, the input is sampled whenever the sequencer moves to the next step (which may be caused by the internal clock or a trigger present on the step input/button). Whether the sampled voltage is stored in the step the sequencer just left, or the one it is moving to, is determined by the Pre/Post switch. If the Auto Stop switch is on (up position), then recording will automatically stop when the maximum number of steps is reached. When recording has finished, the sampled voltages are played back in order by the sequencer on the output jack.

Fax was created with physical controllers in mind. Try mapping it’s big knob to a MIDI controller, or triggering the recording of a keyboards CV output using it’s gate signal.


Luigi is a random digital clock and noise generator. It can use either an external or internal clock.


Monte is a probabilistic trigger sequencer. It can use either an external or internal clock. For each step of the sequence, the probability of a trigger being generated is determined by a CV/knob combo. When CV is present the knobs act as an offset. All of the gates are OR’d to the main output as well as having their own output. Using CV on the Steps input allows for sequences of up to 32 steps.


Planck is a decimator and bit depth reducer. The output of the depth reducer is normalled to the input of the decimator.


PSI OP is a 4 operator FM percussion voice. It’s heavily based on a popular Eurorack hardware drum module, so if you can find a manual for such a module, that’ll explain the functionality until I can write some proper documentation!

By default, PSI OP has a DC offset filter on it’s output. This can be toggled via the context menu. The looping behaviour of the Speed envelope can also be toggled in the menu.

The opal wavetable used in PSI OP is taken from ValleyRack


Rasoir is an asymmetrical voltage processor. It’s based on the the types of distortion found in modules like Autodafe’s FoldBack and HetrickCV’s Waveshape. What makes Rasoir unique is it’s ability to slice a waveform into two components that lie above or below a threshold voltage and process those components seperately. Both high and low components can be shifted in time, clipped, pinched, folded and slewed. The top row of controls and jacks affects the high component, and the lower row the low component. Each component has it’s own output, and they’re combined on the main output. The main output also has dry/wet control and a DC offset filter.

See here for a demo


Sigma is a basic preset voltage adder. Sometimes you just want to add 1V to something!


Wonderful collection! Welcome :smiley: So cool to have the arp sequencer around!


Wow, fantastic set of modules. I’ve just been playing with PSI OP and it sounds excellent!

Not sure what it’s based on but is the sound supposed to vary as much as it does? Sometimes it will sound more clicky and sometimes less so but I’m not sure why (with static settings). It almost sounds like there is some filter or pitch modulation happening?

You can hear it quite clearly with this patch: Kick.vcvm (842 Bytes)

It’s not necessarily a bad thing at all but I would like to understand it a bit more.


There’s no explicit modulation happening beyond the FM which the user has control over, but what the users controls are doing is pretty obfuscated!

In your specific patch, there’s two oscillators contributing to the sound, each with it’s own amplitude envelope A and B, and a master ptich envelope determined by the speed, and start and end frequency controls. Oscillator 1 modulates the frequency of oscillator 2, by an amount determined by envelope B. Envelope A determines the amplitude of oscillator 2 at the output. The pitch of both oscillators is first determined by the main frequency from the pitch envelope, then by a ratio chosen with the ratio knob. Here, oscillator 1 is at half the main frequency determined by the pitch envelope, and oscillator 2 is at pi/4 of the main frequency. You’ve got the end frequency set quite low, so the end result is that the FM is happening at LFO rates, and is thus audible as a slowly modulating sound.

PSI OP is nothing if not unpredictable! It’s heavily based on a popular hardware FM drum module, but I’ve never actually used said hardware. The end result is just what I imagine using it to be like.

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Guessing the ALM Taiko :smiley:

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I had the opportunity to test the github builds, PSI OP is already a favorite, Arpanet is a fun sequencer … still lot of modules to try

nice collection !

I’ve been GASing hard over the module that PSI OP emulates, so I’m very excited to give it a shot!

I have been using Psi Op since it was first available for beta - that was two months ago I think - and it’s never left my rack.

It’s only really capable of one single thing - semi-controlled FM noise. You will never be able to conceal its crunch and metallic tinge. You will never be able to use it to make some tight producer club beats and precisely dial in the sound you have in mind. But if you trust it enough to play with it without a goal in mind, you’ll be able to make thousands of precussive and tonal sounds you didn’t know were perfect for your song.

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Very cool set of modules - thank you!

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These are awesome modules! Thank you!

Congratulations are in order for the presentation of your modules. They have a neat appearance that reminds me of the classic ol’ Moog in black & white. Offering modules with clean faceplates with relevant information without useless visual art is much appreciated.

I’ve added a few small changes:

  • Monte now displays the trigger probability parameter as a percentage rather than as decimal fraction
  • PSI OP has an option to sync the oscillators when it receives a trigger
  • PSI OP has an option for the global FM modulation index to be adjusted by the voltage of the triggers it receives - a trigger of a higher voltage has a higher modulation index
  • Chi shows it’s frequency parameters in Hz rather than arbitrary decimals fractions. Note that the voltage control of the frequency parameter is still in terms of percentage of the filters sweepable range and not in V/Oct. In implementing this I’ve had to reconfigure the sweep of the frequency knobs - they still cover the same range but with s slightly different exponential curve, so the centres of the knobs are slightly off from their previous values.

Botzinger is still early in development so please let me know if there’s any major bugs! Functionality is also subject to serious change…


Rack V2 versions are now up on the library, please enjoy!


Thank you!

I recently found your modules and like them a lot!! Thank you very much!

Cheers, dDom