show and tell, part 1

And here’s the bit where I get into what’s in my modular synth cases, and what I like and don’t about each bit.  I’m going to take it slow, and try to keep things as interesting as I can for people who are new to synths and for more experienced types curious about what I’m using and what I think of it.  As a result, this is going to take a few posts.

Let’s start with the rack on the left side of my desk.  It’s a desktop 19″ rack stand, of the kind you could fill with servers and backup drives, or with mixers and effects.  At the bottom I’ve left one space empty for cable clearance, and then a 1U power switch bank — handy for devices without their own switches, and also for rebooting the router and cable modem without crawling under the desk.

At the top, there’s this:

Left:  A “monitor lizard” who lost his natural habitat back when I went from a CRT to LCD.

Middle:  CV.OCD by Sixty Four Pixels — a very customizable MIDI converter with 4 CV and 12 gate outputs.  With this I can sequence notes, other gates, and synchronize from the computer to modular gear.  I have mine set up so MIDI channel 1 outputs pitch, velocity, gate and an extra trigger; channel 2 and 3 each have pitch and gate; channel 10 assigns five specific notes to gate outputs, and there are three clock sync signals at different divisions.

A quick bit about how Eurorack modular synths communicate:  they don’t use MIDI, they use analog control voltages (CV).   Each patch cable carries one signal.  Signals have no intrinsic meaning and are left to modules to interpret, but there are some typical signal types.  

Frequency (pitch) has a standard of one volt per octave (“V/OCT“).  

Gates, which determine whether a note is held or some other temporary event is active, are either “low” (0V) or “high” (some arbitrary positive voltage).  

Triggers are simply short gates and the important part is the rising edge where they jump quickly from low to high.  

Clocks are triggers that repeat to define timing.  

Audio is a voltage that fluctuates quickly enough to be audible if connected to a speaker.  

Everything else is probably modulation of some sort, though a fixed steady voltage is often called a reference or offset

These signals are mostly interchangeable, with varying standards and consequences — discovering these is part of the fun of modular.

Right:  The thing with the eye is a Bleep Labs Thingamagoop 3000.  It’s a weird sound generating toy with a “LEDacle” that can blink in different patterns and speeds, and a light-sensing eye that responds to it (or other changes in light and shadow).  Good for drones and weird warbly noises, I don’t use it often but it’s fun to play with.  It can generate and respond to CVs too, but it’s much easier to just use it standalone and only tap its audio output.

Bottom:  Focusrite Saffire Pro 40.  This is how I get audio in and out of my computer.  8 analog input channels, some output channels, plus digital I/O that I’m not using, with easily accessible level and monitoring controls on the front.  Perfect for my needs, except it’s Firewire rather than USB and initial setup was kind of a fight.

My top row of modules starts with Manhattan Analog DTA on left.  This one was a prototype unit I bought directly from the maker.  It’s two single channel VCAs in series, plus an extra drive stage to add some saturation and weight.  Not the controls I expected (which would have been a manual bias as well as CV level) but still useful.  Shame it’s AC-coupled.  I’d rate it a 3/5 with no rancor; it’s not exciting but it does its job pretty well.

A VCA, voltage controlled amplifier (or voltage controlled attenuator) controls the level of one signal using another signal — an automated volume control.  Typically you use this to shape the dynamics of a note using an envelope (a signal that responds to a gate with a voltage that rises, sustains and falls according to timing you set).  But there are dozens of other uses, and a cliche phrase you can never have too many VCAs.”

An attenuator is just something that brings the voltage closer to zero, but this is vitally important in modular.  An attenuverter can also flip it between positive and negative.  An amplifier pushes non-zero voltages farther from zero.  All of these are multipliers — attenuation is multiplying by a value between 0 and 1, attenuversion multiplies by a value between -1 and 1, and amplification multiplies by a value higher than 1.

This brings up unipolar vs bipolar signals — which is simply whether negative voltages are expected or ignored.  Audio is bipolar, but the control input on a VCA is typically unipolar — send it a negative voltage and it remains fully silent.

But there are bipolar VCAs which invert the incoming voltage if the control input is negative.  These may be called “four-quadrant multipliers” or “ring modulators” or “balanced modulators” because apparently one term for the same thing wasn’t enough.

AC-coupled means it responds fully only to audio signals; any signal that changes too slowly will fall to zero.  There are some technical reasons why one might want this, but usually DC-coupled is preferable since you can manipulate non-audio signals with it.

The second module is Instruo tanh[3], which has three channels of smooth saturation/limiting of audio or control signals.  This can give audio a bit more of a push or “warmth” depending on levels and usage, can be used to keep feedback somewhat under control, or can be used to give extra curvature and interest to control signals.  I like running envelopes through it to give them a sort of “sticky” feel (words fail a little).  4/5; those mini knobs are tolerable but not lovable and to really help with feedback control it needs an attenuator afterwards, and I feel like two channels with attenuation would have been nicer than three without.

Next in the line is Rabid Elephant Natural Gate, the holy grail of LPGs.  The sound is gorgeous, the panel finish and art are gorgeous, even the box it came in is gorgeous.  It’s extremely controllable and playable, with easily tweaked manual “open” sliders as well as decay times and a 3-way response curve switch.  It also has a tendency to get louder if you trigger it rapidly, which can intensify the drama. I had the chance to try it at KnobCon Six, and bought one within minutes of the release announcement.  Since then the demand has skyrocketed and the price has increased significantly due to the need to switch to a different contract manufacturer.  But it’s soooo good.  5/5!

An LPG or lowpass gate is related to VCAs, but as the control signal decreases, the higher frequencies (treble) go quieter more rapidly.  This can give more natural dynamics and is favored in West Coast synthesis.  

VCAs respond immediately to changes in control voltage, but LPGs close (go quiet) more gradually than they open.  A quick trigger to a VCA would let through a “beep”, but the same trigger to an LPG would give a natural, percussive “ping” or “strike.”  This is such a common usage that some people forget you can use an envelope with an LPG just as with a VCA.

Classic LPGs use an electronic part called a vactrol, which were originally made using toxic materials.  The EU has imposed strict limits on them in recent years.  They also vary a lot in behavior and have to be hand-picked for desirable response.  It’s possible to make vactrols using greener materials, but overall they seem to be falling out of favor, replaced by other circuits or digital emulation.

Soundmachines LS-1 Lightstrip:  a handy touch controller that my spouse bought me last year.  It will generate both a gate and a voltage according to where you tap or slide your finger, can hold the last touched level, and it can record and loop a few seconds of movements.  Run it through a scale quantizer and you can use it like a micro keyboard!  4/5; sometimes the hold or record modes activate when you don’t expect, or don’t when you do expect.

A quantizer takes a signal and “rounds” it to match the nearest note value.  Some round to the nearest 1/12 of a volt, while others let you choose between different scales or define your own.  It’s like imposing frets onto a fretless instrument.  This is great for random signals or imprecise controllers, and can be fun when sliding between notes.

Make Noise Contour is the aluminum one with the vertical row of four white-capped knobs.  It’s a basic ARSR envelope generator similar to Moog designs, with adjustable response curve.  The first envelope I tend to reach for when patching the left rack, it’s just so friendly and easy to dial in.  4.5/5.

Envelopes are often described by various types of stages:  A for “attack” (onsite or rise), “D” for decay (fall), “S” for sustain (hold steady while the gate is high), “R” for release (a separate final decay after a sustain), and “H” for hold (hold steady for a fixed time).

The most common envelope types are:

D:  immediate rapid onset followed by an immediate decay, like a percussion instrument or plucked string, or a vactrol strike.  Gate time is irrelevant, this envelope treats its input as a trigger.  If another trigger is received while still decaying, behavior can vary from module to module.

AD:  rise to maximum, followed immediately by decay to silence.  Again, gate time is irrelevant, and the behavior when receiving a second trigger can vary from module to module.

AR (or ASR):  rise to maximum, sustain while the gate is high, and release to silence.  If the gate is released while still in the attack stage, immediately release.

Many AR envelopes are implemented by slewing an input signal.  That is, if the input voltage rises, the output level rises more slowly.  If it falls, the output level falls more slowly.  If the input happens to be a gate, the result in an AR envelope.  If it’s stepped voltage levels, the result is smooth voltage levels.  If it’s audio, the result is filtered audio (or silence if your attack and release are too slow).  Modules that do this (and also AD, using a separate trigger input) are often referred to as function generators, and typically have EOR (end of rise) and EOC (end of cycle) trigger outputs in order to chain and synchronize other events.

ADSR:  rise to maximum, decay to a specified sustain level, hold while the gate is high, and release to silence.  With a zero sustain level it can imitate an AD envelope, and with a maximum sustain level it imitates an AR envelope.

ARSR or ADSD:  a simplified form of ADSR where the decay and release rates are the same.

Multistage envelopes can have multiple stages of various types, as can vector envelopes which define level over time with a series of X and Y coordinates.  Even rare are “spring” and “bouncing ball” envelopes based on physics models. 

ADSR is the classic East Coast envelope.  AD and AR envelopes, and function generators, are generally associated with “West Coast” synthesis.  AD envelopes typically have a loop switch which allows them to rise and fall continuously, taking the place of the LFO (low-frequency oscillator) which is more typically East Coast.

All this East/West stuff is largely an arbitrary historical distinction between how Robert Moog and Don Buchla designed their synths.  While there’s some truth that certain design philosophies work together well, the “coast thing” should not be taken too seriously!

To its right is Make Noise Function, a function generator that also has a “hold” function that freezes its current level.  Much like Contour, the knob ranges and response just make it super easy and “musical” feeling.  4.5/5.

And then WMD/SSF Mini Slew, another function generator.  This one has more CV inputs and a built-in VCA — it’s cleverly arranged as an attenuverter for one of the module’s outputs, with a bipolar CV in jack.  You can run audio through that CV in jack, and the module’s envelope will control its volume.  But the response of the controls is much more fiddly than Function, the EOR/EOC outputs are a bit flaky, and unless the trigger is above about 6.5 volts, it won’t retrigger during the falling stage — which can be advantageous but it’s an awkward default.  And for some reason it requires twice as much current from the power supply as Function.  3.5/5.

Make Noise ModDemix is next.  This is a pair of bipolar VCAs with kind of a nonlinear twist right around zero that gives it a little extra spice.  There’s also some normalling which straddles the line between confusing and useful.  I should use this more because I often forget it’s there — maybe if I stuck it over on the left side between DTA and Natural Gate it wouldn’t sneak away from me.  4/5

Normalled connections are default connections that are interrupted when you plug something into an input.  For instance, on the DTA, if you don’t plug anything into a CV input, a constant positive voltage is normalled there instead so you can use the knob as a manual volume control.  The same is true of the audio inputs on Natural Gate, so you can use it as a D envelope generator when it’s not processing audio.

The module with the cute pink blob is Alright Devices Chronoblob, a digital delay effect.  I have a lot of delays in software, but it’s good to have at least one in the modular system as well.  What makes this module special is (A) a sync input which lets you lock delays to the beat, (B) the choice of whether to change delay time with a smooth tape-like pitch shift or a clean crossfade that lets you bounce delays all over the place to create interesting patterns, and (C) send and return jacks for the feedback loop which let you affect the echoes or do some other clever hackery.  4.5/5 (a level input knob would have been swell and a clean feedback limiter would have been ultra).

Ending the first row is a Doepfer A-138m matrix mixer.  This has four inputs on rows, four outputs on columns, 16 knobs to assign them, a switch to choose bipolar or unipolar control of each column, and the top row is normalled to a constant voltage.  It can act as a manually controlled voltage source, independent attenuverters or mixers, a handy way to mix sources in stereo, control feedback, rearrange the signal flow of other modules patched into it, and even can be used for sequencing by feeding it combinations of gates.  4.5/5 (higher frequencies can leak through just a little even when the knobs are turned down fully).

A sequencer stores sets of voltages and/or gates as discrete steps, and can play them back synchronized to an internal or external clock.  Sequencer designs vary widely to cover many different needs and styles of composition; some have multiple channels, are rhythm-oriented, can rearrange the step order, and so on.  Since musical pitch is a primary use for sequencers, many have built-in quantizers.  

So that’s what’s in my first row.  Stayed tuned for the other four and the pedalboard & miscellaneous stuff… and then some words about the logic of module arrangement, why I chose one module over another, (unsponsored) recommendations, various sequencing methods I use, and a lot of other blathering. 🙂

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.