VC F3DB stands for Voltage Controlled Fixed Filter Feedback Distortion Bank. The simplest description is it’s an analog 16hp six band voltage controlled fixed filter bank. But with the additions of so much gain, clipping, feedback, and self-oscillation it becomes a very flexible and unique gestural sound sculpting tool capable of; graphic equalization over 6 octaves, multi-band distortion, spectral processing, crude vocoding, multi-frequency envelope following, self-modulation, and even as an instrument on its own. With no input it can be used as a pseudo chaotic “harmonic” feedback oscillator.

To get an idea about the many possibilities, make sure to watch the very interesting 30 minute Youtube demo by Sarah Belle Reid, which is mega interesting, as it goes deep into feedback and no input sound generation techniques.

The filter frequencies were specifically chosen to emphasize more ambiguous and dissonant intervals. Although the frequency bands are spread out over many octaves I purposely tried to leave out “3rds” besides a major 10th at the top frequencies to even out all the dissonance below. But the frequencies aren’t exactly equal tempered, so it’s relative. The bands roughly equate to F2, B3, F#5, C6, F7, A8.

The design is based on the Moog 914 filterbank, which it borrows the frequency bands from. But this circuit uses active filters with opamps inspired by YU Synth opposed to passive cells using inductors on the original. The 88hz is a low pass -24db/oct and 7k is a high pass -24db/oct, the rest are -12db/oct band pass filters all with a Q around 4.

The hard and soft clipping circuit on the input is fairly standard which appears in many different iterations of classic guitar pedals. But it has a lot of gain and can even boost line level signals. What makes it a bit unique is the feedback on the clipping circuit which needs to be turned on by the GFB(gain feedback) switch and the amount can be controlled by the Gain FB pot which can add some fuzz/bite to the signal depending on which clipping switch is engaged or at the extremes it will self oscillate from audio rate to LFO sort of clicking range. All the clipping stages in the module are using silicon diodes.

Consult the Signal Flow Chart to the left for a rough visual breakdown of the controls,in/outs,normalizations, and optional settings for the module.

Each band can also be muted by the top toggle switches or clipped(at the VCA) by the top slide switch which makes this design a bit different than other filter banks. As well as the overall feedback section(bottom middle) takes the sum/all bands out through a VCA(controlled by the feedback pot and FB CV) back to the input gain/clip circuit. and you can also tap into this using different sends/bands to the FB In jack to break the normalization. With this extra feedback “resonance” you can get more whistley and howly filter sounds kinda like the Serge res eq, which can also go into self oscillation.

All CV ins are expecting +5v to open the VCAs (they wont respond to negative voltage), once you get closer to +8v or so it can clip the VCA regardless of the gain settings or clip switches. Output amplitude in high gain settings will exceed 10vpp and can get up to 20vpp. The envelope followers tend to stay around 0-5v out, but with clip switch active they can go up to 10v.

Since this is a high gain module there can be bleed between the bands in certain configurations and situations. Also in high gain modes with higher frequencies the 2.8k and 7k bands can bleed a little with the VCAs closed.

Power: 75mA @+12V, 75mA @-12V

Width: 16 HP, PCB material

Depth: 45mm

This is a Do-It-Yourself kit, not an assembled module. Building instructions can be found here.

DIY level: advanced, no beginner project, cause it is complex! This is a highly involved DIY all through hole project. It is a long build with 5 different pcbs to solder and assemble.

Three channel summed attenuator and mixer in 4HP
Each channel is normalled to the sum(VI) so it can be used as a 2 channel mixer and 1 channel attenuator, or a 3 channel mixer, or as 3 separate attenuators. Normalization to the sum is broken by inserting a jack into the outs of channels I-III. The Attenumixer works well with both cv and audio, although the potentiometers have a linear response. Since the module is passive there will be signal loss at the sum out. Here is a video about it.

Technical Information
4HP
Passive 0mA

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY level: easy

Chaotic voltage generator in 3HP

It is a unique module because it has never existed as an electronic music instrument until now. The module is based on a circuit from a paper called “A simple chaotic circuit with a light-emitting diode” written by Volos, Wang, Jafari, and Kapitaniak.

Diode Chaos produces 3 phases of interrelated morphing voltages including a chaotic trigger out. The range is 20-30 seconds a cycle up to audio rate, although only the X out and TRIG out go up to audio rate. The frequency is controlled by the RATE knob. Each output exhibits different behavior at different rate settings. X,Y, and Z outs like to stay in the 4vpp range although at different RATE settings the outs can reach 10vpp. The TRIG out chaotically releases 0-10v triggers although sometimes it will spit out smaller voltage peaks.
LED soldermask windows provide constant display of positive and negative voltage crossings. Differences between chaos and random (some quoted and summarized material from Ian Fritz’s site) chaos is “highly irregular, but still contained within a finite region (the “strange attractor”)”. Chaos occurs in 3 dimensions chaos needs a non-linear element (with Diode Chaos the nonlinear element is a red LED, and the chaos is directly visible and useable at the TRIG out).

Here is a video about it.

Technical Information
3HP, 45mm Depth
10mA +12V/10mA -12V
Reverse power protection

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY level: easy

Chaotic oscillator and audio mangler!

The Triple Cap Chaos(C^3 Chaos) is a 2hp analog, chaos based, noise oscillator, pseudo ring modulator/harmonics generator, and audio mangler. Video 1, Video 2.

It is a unique module, like the Diode Chaos, because it has never existed as a musical instrument until now. There is also no other module to my knowledge that can do exactly what the Triple Cap can do. The circuit(with several modifications) is based on the paper “Simple Autonomous Chaotic Circuits” by J.C. Sprott and Jessica R. Piper. As opposed to the Diode Chaos that generates control voltage this module focuses on the audio rate.

The “Emanate” potentiometer controls the coarser overall spectrum of the chaos, from lots of activity counter clock wise up to less chaos and more of a steady oscillation. The “Width, CV ATT” potentiometer can be thought of as more of a fine control for the chaos/oscillator. When something is inserted into the “CV” in the voltage normalization from the width knob is broken and the potentiometer now acts as an attenuator for the incoming cv. The Triple Cap is not a traditional volt per octave exponential VCO, and has a sort of narrow frequency range to exploit the chaotic behavior.

It expects a +5v to -5v max signal in to modulate the chaos. The “IN” jack is an A.C. coupled input for audio in, although cv and audio can work for both the “CV” in jack and “IN.” The “IN” will interfere and interact with the onboard chaotic oscillator depending on the frequency of the input, which may take some experimentation. It can create ring mod ish sounds, to added harmonics, to almost bit crushed sounds depending on the “X” or “Y” output. The “X” output is a more windy noisy sinusoidal based output and the “Y” output is more squared off and aggressive, harsher sounding output.

Some quirks about the Triple Cap: The “X” output can offset negatively or positively a little bit depending on the pot settings, but both outputs tend to stay around 10vpp. With the “Emanate” and “Width” pots all the way up the typical frequency will be around 150hz although some will reach 200hz at this setting. With the “Emanate” pot full counter clock wise “Width” pot full clock wise the frequency will be around 250hz. It is possible to send signals into the triple cap that can bring it out of the desired range causing the oscillation to cut out.

The Triple Cap has a double sided panel. meaning one side has the classic graphics and the other is Soulless with less graphics.

Power: 15mA @ 12V, 10mA @ -12V
Width: 2 HP
Depth: 37 mm
Panel: Black FR4

This is a Do-It-Yourself kit, not an assembled module. The kit includes all parts to build the module. Only trough-hole parts to solder. Building instructions can be downloaded here.
DIY level: medium.

https://youtu.be/iItsWYr2zKY
https://youtu.be/7bzmRfKcX28

Dual summed voltage controlled amplifier and mixer in 2HP
It is a DC coupled OTA(LM13700) Dual Linear VCA based on the same fabled design of the VnIcursal VCA. The 2 VCAs are summed together so it can be used as a voltage controlled mixer at the “SUM OUT” or all 3 outs can be used separately and simultaneously. 5 volts into the CV in will provide unity gain, anything above 5 volts can clip the input.

Technical Information
2HP, 50mm Depth
15mA +12V/15mA -12V
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY level: easy/medium

Dual voltage controlled analog oscillator in 4HP
Each VCO has square, triangle, and sine wave out, coarse and fine tuning controls, a control voltage input, and a switch for selecting exponential or linear cv in. When a control voltage is inserted, the fine tune control becomes an attenuator for the incoming voltage. In exponential mode, when the attenuator is fully clockwise, the VCO will track around 5 volts per octave. Here is a Video about it.

Technical Information
4HP, 45mm Depth
20mA +12V/40mA -12V
Reverse Power Protected
Waveform outputs 10vpp

There are a couple quirks to these 8038 VCOs: Below 300 hz the waveform symmetry is slightly off. Triangle waves get a little uneven in the lfo range, the sine is not completely perfect to begin with the bottom trough and in the lfo range it slopes slightly, and the square turns more trapezoidal above 1khz (see scope shots). Also it doesn’t track 1 volt per octave perfectly. Usually the 1st and 3rd octave will be a couple cents off. Other than those idiosyncrasies, it is a powerful, stable dual oscillator in a small footprint with no cross talk between oscillators. It’s great for: drones and beating sine or triangle waves, cross modulating itself for interesting clocks/LFOs, creating complex waveforms/timbres through lin/exp frequency modulation.

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY level: medium

Analog random voltage and noise generator in 3HP
It features sample/track and hold normalled to white noise with a toggle switch for selecting sample(switch right position) or track(switch left position) and hold function. There is also a PCB trimmer(at the top of the motherboard) to adjust the spread(gain) of random voltages out from “scalar” (low gain, counter clock wise) to large interval jumping(high gain, clock wise). All analog white, pink, and brown(red) noise 10vpp~(dependent on lower PCB trim). Smooth(infra red) random cv out at 10vpp with 2 range settings from wiggly with (more events, switch in left position) to almost random rise and fall envelope behavior (less events, switch in right position). White noise pcb trimmer sets the amplitude of the noise which in turn influences the rate of the infra out. LED solder mask windows indicate positive(red) and negative(blue) voltage crossings. Here is a Video about it.

Technical Information
3HP, 47mm Depth
10mA +12V/10mA -12V
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY level: medium

Analog random voltage and noise generator that expands upon the features of the Entropy Euroack Module in 3HP
The Entropy+Expander packs together some of the most random voltage options in 6hp. It provides a controllable “Glide”(slew) out for the S/T\H, a comparator with a controllable rate(“Thrsh”) of random gates(“Rand Gate”) out with an input to compare other waveforms(Comp In, inserting a cable into here breaks the white noise normalization), and high pass filtered white noise resulting in approximate “Blue noise”(+3db/octave) and “Violet noise”(+6db/octave) outs.

The unique part of the circuit is a voltage controlled  A/B switch thats normalled to the “Rand Gate” out that’s switching between the S/T\H out(left Blue led window)and Infra out(right Red led window), the Glide control also effects the S/T\H coming out of the switch so you can get really random results from the “Entropy Out.” Inserting a cable into “Switch CV In” breaks the random gate normalization and lets you toggle between A/B(left S/T\H out and right Infra out, indicated by the led windows) with your own gate or trigger.

There is a jumper on the pcb to select if you want glide on the s/t\h at, Entropy out, or un-slewed operation. There is also a trimmer for setting the amplitude of the incoming signal at “Comp In” which sets the frequency range of random gates. This may have to be adjusted depending on your Entropy version.
The random gate range can also be set up more as a noise oscillator by turning the pcb trim(clockwise) up or it can be set so random gates are extremely slow(trim counter clockwise) with minutes between random gates.Here is a Video about it.

Technical Information
3HP, 45mm Depth
15mA +12V/10mA -12V
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY Level: medium

Simple 3 Band Equalizer in 2HP
It provides boost or cut control over the Low, Mid and High frequency bands of an audio input. The circuit is capable of up to 20vpp~ of boost(with a 10vpp signal) and attenuation down to 1-2vpp depending on the input. The frequency bands are centered near 50Hz(Low), 1kHz(Mid), and 10kHz(High). The circuit is AC coupled and will invert the input. With all the potentiometers at noon, the MinEq passes the signal relatively unaltered.

Technical Information
2HP, 25mm Depth
10mA +12V/10mA -12V
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here. This kit includes 1 SMD component!

DIY Level: easy/medium

Dual summed mute Attenuator, Offset Generator, Mixer, and Mute in 2HP

The newest 666 version (2021) can be powered and will provide Offset of 0-5V with nothing plugged into the “IN” for each channel controlled by each respective Potentiometer. The “Sum Out” will also be able to send out 0-10v~ volts depending on the setting of each Potentiometer. Both channels are normalled to the sum, so inserting a signal into an “IN” will remove it from the “Sum Out. There will be signal loss at the sum out, because the module is passive. Great for cv or audio although the module ships with linear pots. Here is a video about it.

Width 2 HP

Depth 25mm
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY Level: easy

User configurable 3 Channel Unity Gain Audio or Control Voltage Mixer in 2HP

The newly revised MiniMix is now all through hole and aimed more to the beginner solderer. There is also a trimmer on the PCB to increase the master gain up to 2 or more for all 3 channels.

Technical Information
2HP, 25mm Depth
10mA +12V/10mA -12V
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY Level: easy

The Push VCA is a 2 Channel DC Coupled Mute Eurorack Module in 2HP
It features 2 independent unity gain DC coupled VCAs with led push button mutes. A mix of both channels is available at the sum, but all outputs are available simultaneously. The newest version has normalizations to +5v, so with nothing plugged into the ins voltage can be toggled on and off at the outputs and up to 10 volts can be output at the sum. Threoretically there is a latching or momentary push buttons version. But as all folks ever wanted the latching version, we now only have the latching button version. LED button color may vary between red and yellow. A Video can be found here.

Technical Information
2HP, 50mm Depth
50mA +12V/10mA -12V
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY Level: medium

Analog skew-able xfade-able LFO Eurorack Module capable of a plethora of waveforms in 3HP
It has three rate settings ranging from 3 minutes and 30 seconds a cycle up to audio range at 20 hz. Triangle waves can be skewed between ramps and saws, and square waves pulse width can be adjusted from inverted triggers to triggers. The LFO’s unique feature is voltage controlled cross fading through the (“Fade C.V.” in) between square/shark tooth\sine waveforms provided at the “Fade Out.”  All outs are also influenced by the skew knob resulting in many complicated and asymmetrical possibilities at the “Fade Out.” It can even be self patched(ie triangle or square into fade cv) for an extended pallet of waveforms. The “Fade C.V.” in expects a bipolar voltage 10vpp to fade from square to sine with the fade pot at noon position. Bicolor led provides constant display of positive and negative voltage crossings. Here is a Video about it.

Technical Information
3HP, 45mm Depth
15mA +12V/15mA -12V
Reverse Power Protected
 
This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY Level: medium

The SVF 2 pole 12dB State Variable Filter Eurorack Module in 4HP
It provides Low Pass, Band Pass, and High Pass outs inspired by WASP and Thomas Henry filter topologies. The filter has 2 audio inputs, but channel 2 is jumper selectable between standard audio in or Ping-able operation. The 2019 revision also adds improved cutoff and resonance response and attenuversion through the ACV IN using the above pot. CV IN provides another unattenuated voltage input to modulate the frequency.
At the CV in, +10v will open the filter completely if the cutoff pot is CCW(counter clockwise). With the cutoff knob at noon the filter can be opened with +5v or closed with -5v. CV input at the ACV in is dependent on the CV attenuverter knob.
There are also several jumper selectable modes for max resonance, self oscillation or no oscillation based on the setting of the resonance pot.  According to the jumper configuration, the filter is capable of clinical and clean, to juicy and drippy, to low pass gate sounding plonks, to screaming chaotic resonance. When set to self oscillation mode, the filter can produce a sine like wave with no input and a trapezoid like wave in the max resonance jumper setting. In max resonance mode, the filter output can exceed 10Vpp. On the newest version, there is a trimmer on the top pcb to set the lowest cutoff frequency. Here is a Video about it.

Technical Information
4HP, 46mm Depth
15mA +12V/15mA -12V
Reverse Power Protected

This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY Level: easy/medium

The VnIcursal VCA is an 6 Channel VCA Eurorack Module in 8HP
It the smallest, most compact Voltage Controlled Amplifier in the Eurorack market. It provides 6 OTA(LM13700)-based DC Coupled Linear VCAs for Audio or CV. The 6 VCAs are summed together so it can be used as a voltage controlled mixer. Each VCA is normalled to the sum so they can be removed from the mix and used on their own. The potentiometers control the amount of gain, and when a voltage is inserted into the CV in the potentiometers act as attenuators. With a control voltage of 5 volts the VCA will be at unity gain, anything above that can clip the input. LED brightness with or without CV in provides constant feedback of each channels amount of gain.
The VnIcursal is not a perfect scientifically spec’d VCA. Analog VCAs can only close so much, or be so silent. In certain situations based on power supplies and gain stages the VCA can experience some bleed or noise mainly at the sum out as all channels are passively summed then buffered.

Technical Information
8HP, 35mm Depth
30mA +12V/20mA -12V
Reverse Power Protected
   
This is a Do-It-Yourself kit, not an assembled module.  Available as Full Kit and Panel/PCB.

Building instructions can be found here.

DIY Level: medium

Original Zlob Modular Blank Panels
Blanks are made of printed circuit board material and they are 1.6mm thick(0.063″). The pure black sides can have slight imperfections because of the manufacturing process. Note, the 2hp blank is not black on the reverse graphic side.

The 1hp blank is black/blank on the reverse side. // The 2hp and 4hp blanks designs are based on a Turkish carpet motif representing ram horns(boynuz): a symbol of power. // The 3hp and 6hp blanks are designed using the hilbert curve fractal.