North Coast's complex VCO is comfortable on a journey to the East or the West, while providing a stable foundation at home in any Eurorack. The module contains two triangle-core VCOs, each with four waveforms and standard V/octave control. As basic VCOs running independently these can be the heart of a traditional subtractive East Coast synthesizer. But the Middle Path's oscillators can also be used together, with or without sync, to drive its unique multi-output Gilbert-style sine shaper. The shaper, which can also take external input, offers wave shaping, distortion, folding, phase modulation including through-zero, and imitation stereo. These effects take the sound into West Coast territory.

The design emphasis is on harmonious combination of simple principles. The exponential converter uses premium analog multipliers and a transistor array to ensure temperature stability without fiddly adjustments or hard-to-control "tempco" resistors; it should provide consistent tracking, and especially between the two oscillators, without needing to warm up. The triangle cores are intrinsically frequency-accurate without needing extra circuitry to compensate for reset time. The sine shaper includes our own novel quadrature modification which can be used to generate a stereo signal or in combination with other modules to create frequency shift effects. The sync circuit joins the oscillator cores in another way with a selection of soft and firm modes.

• High-quality potentiometers with bushings fastened to the panel for wobble-free operation; conductive plastic for smooth feel

• Normalization to the Eurorack bus allowing it to receive pitch control without needing an input patch

• All-new design, not a clone or imitation of anything else. Innovative quadrature sine shaper offering through-zero phase modulation with a range of up to 1080°

• Genuine AD633 and THAT320 chips in the exponential converter; sockets on all DIP ICs

• Through-hole for easy hand construction and maintenance

• Connectors between boards, and panel controls mounted on a board - no flying wires

• No compromises on build quality: real aluminum panel, not PCB material, with colour printing; panel screwed solidly to both the PCBs and the pots and jacks, for maximum ruggedness; nickel and gold plating on the circuit boards; close-tolerance metal film fixed resistors.

• Fully open design - no lock-in

Power: 75mA +12V, 105mA -12V, reverse-connection protected

Width: 24 HP

Depth: 36mm

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

DIY level: Medium. All through-hole. Multimeter & oscilloscope are recommended for adjustment.

There are hundreds of analog synthesizer VCFs, but only a few core designs. You've got your Moog transistor ladder and imitators that use diodes or other substitutes; you've got your two-pole state variable filter, maybe cascaded to get additional poles; and that's about it. Your grandmother was making electronic music with these designs in the 1960s, and not much has happened since. There are a few more options available in digital and semi-digital (such as switched-capacitor) architectures, but most analog designers have given up trying to create really new filters. Instead, they compete on how well they can imitate or clone specific "vintage" filters. Here is a demo video by DivKid.

The North Coast Synthesis MSK 007 Leapfrog is new and different, with a sound all its own. The fifth-order "leapfrog" core topology, with five integrators and multiple feedback loops, originates in scientific work more recent than the 1960s and as far as we know never before available in a modular synth VCF. The near-elliptic response curve has an extremely sharp cutoff, with ripple in the passband and nulls in the stopband at frequencies chosen to be musically relevant. Sweep the cutoff and hear each harmonic pop into existence and wobble around before the next one arrives. Choose a timbre, and the temperature compensated volt per octave tracking will keep it consistent across the frequency range. Change it up with exponential and linear frequency modulation. There's even a built-in VCA, because you can never have too many VCAs.

• High-quality potentiometers with bushings fastened to the panel for wobble-free operation; conductive plastic for smooth feel; rated for one million operations lifespan (compare to fifteen thousand or less for typical cheap pots)

• All-new design, not a clone or imitation of anything else

• Ultra-sharp five-pole near-elliptic low-pass response, 61dB/octave at the least steep part of the main cutoff slope, with peaks and nulls at musically relevant frequencies

• Built-in VCA switchable to feedback or output modes from the front panel - no jumpers

• Temperature compensated V/octave tracking

• Through-hole for easy hand construction and maintenance

• Connectors between boards, and panel controls mounted on a board - no flying wires

• No compromises on build quality: real aluminum panel, not PCB material, with colour printing; panel screwed solidly to both the PCBs and the pots and jacks, for maximum ruggedness; nickel and gold plating on the circuit boards; polystyrene integrator capacitors; close-tolerance metal film fixed resistors; multiturn trimmers.

• Fully open design - no lock-in

Power: 70mA +12V, 65mA -12V, reverse-connection protected

Width: 16 HP

Depth: 58mm

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

DIY level: intermediate to advanced, because of the number of parts and adjustment steps. All through-hole. Multimeter and dual-trace digital oscilloscope are recommended for adjustment, with other options possible.

Master of Melodies! The MSK 008 Voltage-Controlled Octave Switch is a multifunction voltage processor. The module has two channels, each containing a whole-volt quantizer that maps its input to the nearest integer number of volts from -2 to +2; a three-position toggle switch that shifts the quantizer boundaries up or down by a volt; and a precision adder (with optional subtraction function). Check some videos here and here.

If you simply route a pitch CV through one of the unquantized CV1 inputs, it can be a performance control, allowing easy transposition up or down an octave at the flip of a switch. That might be useful for VCOs without their own built-in octave switches. With no input signal, it generates a selectable offset of -1, 0, or +1 volts; feed that into an attenuated exponential FM input somewhere and you get the same tactile control over any other interval transposition you choose.

But the possibilities really open up when you start using more inputs. An LFO into the quantized input gives the effect of flipping the octave switch under CV control, keeping your hands free to wiggle elsewhere. Using the unquantized inputs, which are normalled across the two channels, you can transpose one sequence by another. The CV2 input can add or subtract, selectable during build by a solder jumper on the circuit board; in a default build, CV2 adds on the left channel and subtracts on the right, but do-it-yourselfers can change this selection, or design their own expanders to make it switchable on the fly.

Combining the two channels, with or without other utility modules, allows more complex melody-shifting effects. And it doesn't have to be just for oscillator pitch control. Switching fixed-voltage offsets on filter cutoffs also makes for great drops and timbral shifts. (And try putting the result through a slew limiter!) The default sum and difference configuration allows the module to act as a "mid-side" encoder or decoder. With other patching it can be a flip-flop or a wavefolder.

The MSK 008 is fast enough to work on audio. The quantizer is built from hardware comparators, without a microcontroller, and it can do simple bit-crushing effects across the whole audio spectrum. Each channel can also be a unity mixer for audio, with two regular inputs plus the output of the bit-crusher.

• Two channels and multiple CV functions in a small space

• Flash-style comparator quantization - no microcontroller

• Through-hole design for easy hand construction and maintenance

• Connectors between boards, and panel controls mounted on a board - no flying wires

• No compromises on build quality: real aluminum panel, not PCB material, with colour printing; nickel and gold plating on the circuit boards; close-tolerance metal film fixed resistors; multiturn trimmers.

• Fully open design - no lock-in

Power: 45mA +12V, 50mA -12V, reverse-connection protected

Width: 8 HP

Depth: 43mm

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

DIY level: Easy. All through-hole. Accurate voltmeter (or a tracking VCO and some way of measuring its frequency) needed for adjustment.

A filter with a twist! The Coiler Multi-mode Filter and Rectifier packs an entire nest of sound-shaping features into a single 8HP Eurorack module. It's a two-pole state-variable filter based on a unique integrator design which stores energy in both inductors and capacitors depending on the frequency range. The transition region between the two components, and the saturation characteristics of the traditional OTA-based amplifiers, offer warmth and ever-shifting timbres in the midrange, along with hissing highs and slithering lows. This is a somewhat unpredictable filter. Check out some videos here and here.

With simultaneous low-pass, band-pass, and high-pass outputs, the Coiler works well in traditional subtractive patches. But its built-in full-wave rectifier is also great for adding harmonics and distortion in patches from the other coast. When combined with low-pass, the rectifier allows the Coiler to serve as a basic envelope follower, for compression and external-signal patches. It's a lot of bite for the buck, and for the rack space.

• High-quality potentiometers with bushings fastened to the panel for wobble-free operation; conductive plastic for smooth feel; rated for one million operations lifespan (compare to fifteen thousand or less for typical cheap pots)

• All-new circuit, not a clone or imitation of anything else

• Through-hole for easy hand construction and maintenance

• No compromises on build quality: real aluminum panel, not PCB material, with colour printing; nickel and gold plating on the circuit board; close-tolerance metal film fixed resistors.

• Fully open design - no lock-in

Power: 25mA +12V, 25mA -12V, reverse-connection protected

Width: 6 HP

Depth: 46mm

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

DIY level: Easy. All through-hole. Accurate voltmeter needed for adjustment.

The MSK 010's Wien-bridge oscillator cores produce low-frequency sine waves natively, in a fully analog way with a minimum of harmonic distortion. There are no glitches from waveshaping or stair-steps from insufficiently filtered digital-to-analog conversion. Modulate synthesis parameters with these for smoothly evolving timbres and mind-expanding soundscapes. Because the cores are fully independent and will not synchronize, a patch using multiple LFOs will not repeat its modulation state for a long time, if ever. Check the video here.

Choose one of three variants of this module, each with its own set of eight nominal frequencies and cycle times. There are no duplicate or near-duplicate frequencies between different variants, so with two or three, you get the full benefit of a larger modulation palette. Note that the nominal frequencies are just that; every module will have its own one-of-a-kind pattern of exact output frequencies within a few percent of the nominal values, due to component tolerances.

• Variant A - 16mHz, 60mHz, 190mHz, 410mHz, 720mHz, 1.3Hz, 4.8Hz, 16Hz (63s cycle time down to 63ms)

• Variant B - 34mHz, 88mHz, 160mHz, 280mHz, 600mHz, 1.8Hz, 3.4Hz, 11Hz (30s cycle time down to 94ms)

• Variant C - 28mHz, 72mHz, 130mHz, 340mHz, 2.2Hz, 4.1Hz, 7.2Hz, 8.8Hz (35s cycle time down to 110ms)

• Imagine having enough LFOs to modulate everything.

• All-new design, not a clone or imitation of anything else

• Fast starting - full amplitude oscillations within one cycle of power-up, unlike the usual behaviour of an oscillating filter

• Through-hole design for easy hand construction and maintenance

• Connectors between boards, and panel components, mounted on the boards; no flying wires

• All three variants build from the same bill of materials; one full kit or PCB set can be used to build any one variant of your choice.

• No compromises on build quality: real aluminum panel, not PCB material, with colour printing; nickel and gold plating on the circuit boards; close-tolerance fixed resistors and integration capacitors.

• Complete technical documentation released under GPL

Power: 40mA +12V, 40mA -12V, reverse-connection protected

Width: 8 HP

Depth: 43mm

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

DIY level: Easy. All through-hole. No adjustment or trimming.

The Joy of Mix! North Coast makes the Eurorack four-knob utility mixer sound great again with this minimalist design featuring just six transistors. Where a conventional mixer would typically require at least five operational amplifier units each containing a dozen or more transistors, we cut the complexity and distill mixing to its essence. This is a new design made with current components and modern manufacturing quality; but its Class A amplifiers operate on principles that go all the way to the dawn of electronic signal processing.

Suitable for both audio and control voltages, with bonus features that don't compromise the minimalist philosophy: positive and negative offset; simultaneous DC- and AC-coupled outputs; maximum gain a little over unity for when you need that extra push over the cliff. It can also function as a transistor distortion effect, by offsetting the signal until it clips and then using the AC-coupled output.

• High-quality potentiometers with bushings fastened to the panel for wobble-free operation; conductive plastic for smooth feel

• All-new design, not a clone or imitation of anything else

• Classic discrete-transistor design style; DIY kit ships with silicon 2N5088 transistors for a clean modern sound, easily modifiable to use other recent or "vintage" types

• No ICs!

• Through-hole for easy hand construction and maintenance

• No compromises on build quality: real aluminum panel, not PCB material, with colour printing; nickel and gold plating on the circuit board; film output coupling capacitor; close-tolerance metal film fixed resistors.

• Fully open design - no lock-in

Power: 9mA +12V, 14mA -12V, reverse-connection protected

Width: 6 HP

Depth: 34mm

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

DIY level: Easy. All through-hole. Multimeter recommended for adjustment.

North Coast's Transistor ADSR is a four stage traditional envelope generator for Eurorack synthesizers. With full control of four stages, it can shape percussion notes like an AR envelope, organ notes like an ASR, but also the complete range of acoustic-style and classic-synth notes which the simplified envelopes in some popular multi-modules just cannot handle. Use it in subtractive patches for amplitude or filter cutoff, or branch out into controlling other functions, like vibrato amount.

At a svelte 6HP and only 33mm deep, the Transistor ADSR can fit in almost any rack. A Schmitt-trigger input allows it to trigger from slowly changing voltage sources, opening the door to special effects like gate delay when the MSK 012 is triggered by another envelope (or another MSK 012). Three timing ranges controlled by a rugged front-panel toggle switch cover a wide range of musical applications, with the fastest settings allowing the envelope to run well into the kilohertz range for audio-rate effects and signal conditioning. The smooth conductive-plastic potentiometers are a tactile joy to play and pay for themselves with increased lifespan.

• High-quality potentiometers with bushings fastened to the panel for wobble-free operation; conductive plastic for smooth feel

• All-new circuit, not a clone or imitation of anything else

• Classic discrete-transistor design

• No ICs!

• Through-hole for easy hand construction and maintenance

• No compromises on build quality: real aluminum panel, not PCB material, with colour printing; nickel and gold plating on the circuit board; poly film timing capacitors; close-tolerance metal film fixed resistors.

• Fully open design - no lock-in

• Input attack voltage: 2V, release voltage 1V.

• Output voltage range 0-8V.

• Times: attack 50µs-1.8s, decay 6µs-6.5s, release 8µs-9.5s

Power: 10mA +12V, 5mA -12V, reverse-connection protected

Width: 6 HP

Depth: 33mm

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

DIY level: Easy. All through-hole. No adjustments needed.