Configure Your Modular Synthesizer

The three numbers that decide everything

Before you choose a single module, know these three numbers for your case and every module you plan:

• Width (HP). 1 HP is 5.08 mm. A row in a typical case is 84 HP or 104 HP wide. Add up the module widths and leave some space free.
• Depth (mm). Skiffs and shallow cases often fit modules of only 25–40 mm. Check the module depth, including the power cable, against your case.
• Power (mA). Every module draws current from the +12V, −12V and sometimes +5V rails. Total each rail separately and stay below about 75–80% of what your power supply delivers.

Building your own case? See Building a Eurorack Case and Powering your case with the RT-65B.

1. The minimal voice (one row, about 60–84 HP)

The smallest system that still feels like a complete instrument. It makes one sound at a time, but you learn every building block:

• Something to play it: a MIDI-to-CV interface (keyboard or DAW) or a simple sequencer.
• VCO: the sound source.
• VCF: shapes the tone.
• Envelope + VCA: make notes start and stop.
• LFO: slow movement (vibrato, filter sweeps).
• Utilities: a mult and an attenuator, which you will use more than you expect.
• Output: brings the Eurorack level down to line level for your mixer or audio interface.

Leave 15–25% of the row empty. The next module you want is never the one you planned.

2. The complete voice (two rows, 84 HP)

The second row turns a single voice into something that plays itself:

• A second oscillator and a mixer for detuned, thicker sounds, or for using one VCO to modulate the other (FM).
• A sequencer and clock divider so patterns run without a keyboard.
• A quantizer so random or LFO voltages land on musical notes.
• Sample & hold or random for evolving patches.
• One effect, often a delay, to give the voice space.

This is the size where most people discover what kind of music they want to make with modular. That makes it the right moment to plan your next step in ModularGrid (see below) before buying more.

3. Two voices and drums (two rows, 104 HP)

Now the case can play a bass line, a melody and a beat together. Typical additions:

• A second filter and VCA path, so each voice has its own sound.
• Percussion modules: kick, snare and hi-hat voices, or one multi-drum module.
• A sequencer with several tracks, plus a central clock.
• A stereo mixer and a reverb to glue everything together.

At this size, the power supply becomes important. Add up the +12V current carefully: digital modules and drum voices often draw a lot. Our guide to the RT-65B and bus boards shows how to calculate it.

4. Performance and studio systems (three rows or more)

Large systems (3U × 3 rows, 6U × 2, or several cases) are less about having ‘more’ and more about flexibility:

• Complex oscillators, wavefolders and low-pass gates for West Coast sounds (see Patching Techniques).
• Function generators, logic and matrix mixers to create relationships between voices instead of just more voices.
• Samplers, granular processors and stereo effects.
• MIDI/USB interfaces to sync with a DAW or drum machine.

Large cases need more planning: several power supplies or zones, careful cable routing, and a layout where the modules you touch most sit closest to you. Many experienced users also split one large system into two smaller ‘themed’ cases that each tell a clear musical story.

The easy start: a semi-modular synth

A semi-modular synth is a complete synthesizer with the most important connections already made inside (normalled). It makes sound the moment you switch it on, without a single cable. The patch bay lets you override those connections, so you learn modular patching step by step.

Why it is such a good first step:

• No dead ends. Pull out all cables and you are back to a working sound.
• Fixed cost. You get oscillator, filter, envelope, VCA and often a sequencer for the price of two or three modules.
• It grows with you. Its patch points connect directly to Eurorack modules with standard 3.5 mm patch cables. Several models (like the Moog Mother-32 and DFAM and the Arturia MiniBrute 2S) can also be removed from their case and mounted in a Eurorack rack.

How to expand: start with a small skiff (for example 60–84 HP) next to your semi-modular. First add modulation (an extra LFO and envelope), then a VCA and a mult, then an effect. Each module now has an instant job, because the semi-modular provides the voice.

Moog Mother-32 – Classic analog East Coast mono synth with a Moog ladder filter, 32 patch points and a built-in 32-step sequencer. 60 HP, so it also fits in Eurorack.

Moog DFAM (Drummer From Another Mother) – Analog percussion synth with an 8-step sequencer. It pairs perfectly with the Mother-32: the two can be patched together and stacked into a two-tier rack.

The DFAM produces kicks, toms, metallic hits and strange bleeps. Patching its envelopes and sequencer outputs into a Mother-32, or into your first modules, is a great lesson in how modulation and sequencing work.

Arturia MiniBrute 2S – Analog mono synth with 48 patch points and a 3-track, 64-step sequencer instead of a keyboard. Very powerful for its price, and it can be mounted in Arturia’s RackBrute Eurorack case to grow into a full system.

Intellijel Cascadia – A deep, larger semi-modular that combines East and West Coast ideas (wavefolder, low-pass gate, through-zero FM). Great if you already know you want a big system, but more to learn than the others.

Make Noise 0-Coast – A compact synth that mixes East and West Coast synthesis. A popular first instrument for many years; check current availability, as Make Noise has been updating its line-up.

Cre8audio East Beast – A budget-friendly East Coast semi-modular (40 HP when removed from its case). Often sold out, but worth looking for second-hand.

Planning with ModularGrid

ModularGrid is a free online rack planner and module database for Eurorack and other formats. You choose a case (or create a custom one for a DIY case) and drag modules into it. ModularGrid then calculates for you:

• HP used and HP free per row;
• total power draw on +12V, −12V and +5V, compared to your power supply;
• module depth, so you can spot modules that won’t fit a shallow case;
• an estimated total price.

Every module has a page with its specs, a manual link and user photos, and you can browse thousands of public racks from other users for inspiration.

When to use it

• Before your first purchase. Build your dream system virtually, then remove modules until it fits your budget and case.
• Before every new module. Check that the HP, depth and power still work. This is the best protection against an overloaded power supply.
• When rearranging. Try new layouts virtually before unscrewing anything: put related modules side by side so patch cables stay short, keep the sequencer and controls within easy reach, and keep audio outputs near your mixer side.
• When planning a DIY case. Create a custom case with your own row widths and power supply values (for example the MEAN WELL RT-65B) so the totals match your build.
• When selling or trading. Share a link to your rack so others see exactly what you have.

Tips

• Power and depth values are often entered by users. Check the manufacturer’s manual before trusting a tight power budget.
• Save several versions of your rack to compare ideas side by side.
• Search public racks by module name to see how other people combine it.