Synthrotek is an electronic circuit design business specializing in lofi, DIY and Analog noise making and synth kits. Here you will find resources for making great Modular, console and other electronic kits for the electronic musician.
Motomouth is an analogue 3-Band, Sedra + Espinoza Bandpass Filter (DABP) with resonant frequencies that are tuned to the same resonant frequencies found in the human mouth and nose cavities, and these can be varied, independently, to form different ‘mouth shapes,’ to emulate vowels such as A, E, I, O and U. Motomouth can emulate 16 vowels and ‘morph’ or ‘glide’ between each vowel using a single Control Voltage input (1V/Oct), and a Gate to ‘snap’ to each vowel when required. Two of the bands (F1 and F2) are used to form the mouth cavity, and the third band (F3) is used to from the nasal cavity, which is reasonably static. Varying F3 makes little significant difference ‘in the mix,’ but having it is important. The single Control Voltage is decoded to control F1 and F2 independently, because the frequency bands for each vowel are not proportional to each other over the vowel range. So Motomouth has learned how to ‘speak,’ so to speak, but it still needs to learn more, and that’s where you come in. KEY Features:
Single CV to control and set vowel shapes.
Automatic morphing and morphing rates to each vowel.
Pure analogue signal path from input to output.
Gate-operated snap to each vowel when desired.
Sedra+Espinoza Analogue Filter design for a high, sharp Q value and a 12 dB/octave roll-off slope.
Plays well from a monophonic keyboard or Midi Keyboard through a Midi to CV/Gate converter.
Works great with a CV Step Sequencer.
Filter and vowel mode selection using the same single CV input.
Module width: 12HP
Module depth: 42mm
Limaflo Motomouth Formant Filter - DIY available at Synthrotek - YouTube
The Random Sequencer generates quantized random or 8 or 16 step randomly generated sequences, which is great for quickly (and musically) starting a patch, augmenting a patch, and performing live! It generates quantized voltages between 0 and +4V. In the sequencer modes, the module repeats the last 8 or 16 randomly generated steps as a sequence. In addition to being used as a random module, it also doubles as a master clock generator, ranging from 8ms to 50 seconds.
Random mode select jack: selects fully random, 16-step sequence or 8-step sequence
Clock rate control
Clock reset jack: resets the clock when it receives a +5V pulse, useful for syncing with external clocks
USB Power is a light-duty Eurorack power supply designed for mini systems, for testing, and for portability. Plug in a single module, a flying bus cable for multiple modules, or plug it directly into a bus board header. The small PCB footprint was specifically designed to fit our Bus Cheeks systems, but it can easily fit a small enclosure and won’t take much space on your workbench. If you plan using this supply to power the 5V rail on your modules, keep in mind that the 5V rail will sag as you increase your current draw on either or both of the +12 and -12 volt rails.
Plugs into a USB wall wart, USB battery pack/power bank, and USB car cigarette lighter adapter (plugging into computer is not recommended; see information below)
LED power indicators for +12V, -12V and +5V rails
Noise filtering capacitors
Holes for easy mounting to your case or workbench
USB cable included (1.5 ft)
PCB dimensions: 50mm x 28mm
PCB standoff hole size: 3mm
*The amount of 5V current available will vary depending upon the current draw on the +/-12V rails.
The TURN module is a simple device that delays startup to parts of a Eurorack system in order to avoid inrush current problems. It connects between bus boards (or between a Case Power and a bus board) so only that each bus board is powered on one at a time. With two channels, it can delay startup between three bus boards.
The TURN can be used with any manufacturer’s bus boards. It has molex connectors on the back for easy installation, but if you don’t use Synthrotek products, you can attach our Molex Adapter Cables. These cables have a molex connector on one end and bare tinned wire on the other. They can be used with screw clamp headers, soldered into bus boards, or even used with spade connectors (if female spade connectors are added to the tinned wire ends). Only one of the ground wires needs to be used; the other two can be clipped.
Save valuable HP by installing the TURN switches in the side of your case! The TURN can be purchased as a PCB without a panel; when mounting into your case, the LEDs and standoffs are not needed, so only two holes are necessary (for the switches). Specifications:
Module width: 4HP
Module depth: 50mm (with cables plugged in)
Max current draw: 8mA
You can buy this product at fine dealers worldwide or HERE.
Low pulsing drones, dive bombs and high-pitched laser sounds! This drone monster has six square wave oscillators with a delay, essentially combining two 4093 NAND Synths and one Cosmic ECHO.
The Nandamonium has two SAG CV inputs. When the CV jack is patched and the switch is toggled to “CV,” the NAND circuit is powered directly by the incoming voltage. Beyond controlling pitch, the incoming CV can also be used to create lofi rhythmic effects.
Dial in your drone with the Nandamonium!
Six tunable square wave oscillators and two level controls
Delay rate, mix, and feedback controls, with touch control over the rate and mix
Warp switch: adds a bright, “small” speaker tone
Blast switch: introduces max feedback into the circuit momentarily, great for adding rhythm and strange sounds
Two SAG CV inputs, one per NAND synth
CV/On Switch allows selection of CV control or internal power control (1 switch per NAND synth)
This simple 2HP passive mixer is suitable for mixing both audio and control voltage sources. Three channel inputs mix down to one output.
It is not suitable for additive voltage applications. All the jacks are switched to ground to minimize external interference when not patched. This can lead to unwanted attenuation of the output signal unless you plug a dummy cable into the unused channel(s) or, even easier, you can turn the channel’s pot completely CCW.
The LPG is a West Coast Synthesis staple! Our dual Low Pass Gate creates organic percussion timbres, paving the way for sonic exploration with a Buchla/Subotnick vibe.
The LPG has two identical low pass gates in one module. Its unique non-linear qualities emulate percussion timbres like congas, bongos, plucks, etc. The LPG is vactrol based, which creates natural-sounding decays. When the CV input is pinged by short/fast envelopes, it results in more organic sounds like bongos. The slide pot functions in two ways: when the the CV input is not patched, it attenuates/mixes the audio signal. When the CV jack is patched, it attenuates the output level and changes the timbre of the audio signal.
Each LPG channel can be used as a VCA. VCA mode bypasses the low pass filter and resonance and doesn’t color the sound of your input audio. The vactrol gives the VCA a living, breathing, non-linear response.
We tested a number of vactrols for this module, and we liked the pre-tested NSL-7053 best of all. The NSL-7053 has a slower response and a more exponential response curve. The VTL5C4 has a slightly faster response and a more linear response curve. But the LPG will work with a number of different types/brands, including dual vactrols. In fact, each channel can be built with a different set of vactrols.
Synthrotek’s Eurorack Case Brackets are designed to fit flush inside your custom Eurorack case, avoiding unsightly holes on the outside of your case. Includes rail-mounting screws and case-mounting screws.
Available in 1u and 3U, these brackets will work with Synthrotek’s rails or Vector brand rails.
The Quadrangle is quad cascading triggered envelope generator with bipolar output attenuversion. Each channel has voltage control over attack and decay/release, end of attack and end of cycle trigger outputs, and mode (AR, loop and AD). Each channel’s EOC is normalled to the next gate input, resulting in interesting rhythmic opportunities. Channel 4 has a “stop” or “continuous looping” switch which allows either a “one shot” cascaded envelope or continuous cycling. The SUM output allows for longer and more dynamic bipolar envelopes, perfect for interesting modulation. Users also have voltage control over all of the attacks and decay/releases simultaneously when using the ALL A and ALL D/R input jacks. Massive function generation, modulation, rhythm and versatility sets the Quadrangle in a class of its own.
4 Cascading envelope generators
Attenuverters for each envelope output (dial in that secret sauce!)
Attack, Decay/Release and Loop modes per channel
From super fast ~2 mS (Audio Rate) envelopes, up to 8 second envelopes
CV over Attack and Decay/Release per channel
CV over ALL Attack and ALL Decay/Release
Bipolar Voltage SUM output of all envelopes
End of Attack & End of Cycle trigger outputs per channel
Normalled EOC to next channel Gate input (broken when jack is patched)