On Saturday the 2nd of April I’m organizing a course in synthesizer techniques and sound design (in Dutch), location: Nijmegen. Read more about it, and subscribe here: https://riversynths.com/synthworkshop
I’ve been getting a lot of questions about ‘the synth in the banner’, so it’s time time to reveal the details about this rather special instrument.
Roughly 12 years go, after having brought back to life quite a few vintage synths, I felt like building my own instrument. For a year I have been working on the idea, drawing diagrams, searching for parts, and trying various circuits. At that time, I didn’t feel comfortable designing all the electronics myself, so I chose the safe(r) route and decided to use Oakley sound circuit boards for the crucial functions in the audio path.
Since I’m about 50% live performer and about 50% studio nerd, I had special wishes for this new synth. First of all, I was hoping to build a synth with “that” analog sound (the sound on records by Pink Floyd, Yes, ELP, etc). I wanted to have these sounds easily accessible for live use, yet keep the options for more complex studio sound design open. After considering something fully modular, I chose to keep it semi-modular (think Korg MS-20). Internally, all modules (functions) have a default connection, such that you can instantly play them, but also provide access points on a patch panel for more complex routing. Finally, I decided to go with these modules:
- 3x VCO
- 3x VCO octave switcher
- 1x MidiDAC
- 1x Super Ladder VCF
- 1x Steiner Synthacon VCF (years before Arturia built it into the MiniBrute…)
- 2x ADSR/VCA
- 1x VC-LFO
- 1x Equinoxe Phaser
- 1x Ring Modulator
- 1x dual VCA
- 2x dual CV mixer
- 1x sample & hold
- 1x lag generator
- 1x noise source (white, pink, IR)
- 1x Output stage + headphone amp
- 1x Power distribution board
Some circuit boards were already etched (the Oakley Sound ones), other modules were (re)designed and etched by me. In the pictures below you can see how these boards transformed into the Ocean synth.
A couple of months later the Ocean was announced ‘Keyboard of the month July (2006)’ in the international Keyboard Magazine. Michael Gallant writes: “… the Ocean is one beautiful monster of a keyboard”.
After completion I recorded a short piece of music with a lot of use for the Ocean (all, except drums, mellotron and strings). I apologize for it sounding slightly dated, given modern recording quality standards.
The camera has been running hot! Here’s a demo video of the new Nucleus filter.
In the workshop section you’ll find video’s of how the Crux and Nucleus modules are made from a DIY kit. Documents with detailed DIY instructions for the kits can now be found on the Crux and Nucleus product pages.
Here’s a video showing the assembly process of a Crux DIY kit.
Here’s a video showing the assembly process of a Nucleus DIY kit.
If you are into electronic music or music production you are most likely using VCAs. With or without knowing. They can be found in for instance analog synthesizers, effect devices, analog mixing desks, guitar pedals. If the abbreviation isn’t yet familiar to you, it will be by the end of this post as I will have used it 22 times by then.
In its simplest form, a VCA is nothing more than an amplifier with an input and an output for signals to be amplified, and a Control Voltage (CV) input that allows you to control the amount of amplification. With a high CV you get lots of amplification, with a low cv you get little amplification. You could almost say it’s a volume knob that gets controlled by voltage rather than by hand. Another way to look at VCAs is as a multiplier:
output = CV x input
With the exception that in regular VCAs this doesn’t work for negative CVs. If that’s what you want to do, you need a balanced modulator (a.k.a. ringmodulator).
In the case of VCAs in analog synthesizers, there are a three peculiarities worth knowing:
‘A’ for amplifier
While the A stands for amplifier, most synthesizer VCAs are actually voltage controlled attenuators. This means that when they are fed with the lowest possible CV, they attenuate the input signal to (almost) 0 and put out (nearly) nothing. When the highest possible CV is fed in, they do not attenuate at all. When they don’t, most VCAs pass the input signal to the output at ‘unity gain’: the level of the output remains identical to the signal input.
Lineair and exponential
I’ve been writing about the lowest and highest possible CV so far, but what happens to the attenuation in between these values? Well, that depends… At least you can expect the amount of attenuation to follow the CV smoothly from one value to the next, because of the nature of analog electronics (continuous, so no discrete steps, like in the digital world). In one category of VCAs, the attenuation follows the CV linearly. This means that when the CV doubles the ‘amplification’ also doubles (or actually the attenuation halves). This is called a ‘linear response’ VCA, and when amplification is drawn in a graph as a function of CV you will see a straight line.
The other category is called ‘exponential response’ VCAs. These respond exponentially to incoming CVs. You can think of it this way: when you imagine a CV evenly and gradually rising from 0 to 5V, the exponential response makes the VCA’s output rise faster and faster as the CV gets closer to 5V. In a graph it looks like a curve (see figure above). Physically, this exponential response bears important similarities to the way we perceive loudness of sounds, meaning that it is very useful when synthesizing the loudness contours of a sound.
A VCA is not just a VCA
While amplifying or attenuating signals seems like a trivial task, an analog VCA often does a little more. Design choices, component selection and component limitations all impose a subtle character on the sound fed through the VCA. This character often becomes more prominent with higher signal levels, when the VCA is pushed into saturation.
Now you know the basics of VCAs. If you feel like experimenting with VCAs a bit, don’t forget they can do so much more than merely control the loudness of a sound (hint: how about using them to control the depth of filter envelopes with your keyboard velocity, or to gradually fade in vibrato with an envelope after a note is held).
Hi! It’s been a very hectic, but encouraging end of the year. Months of hard work have been brought together last couple of weeks into the release of the first two River Eurorack synthesizer modules: the Crux VCA and the Nucleus VCF.
Hello world! Welcome to the new River website. Content and features will gradually be added in the next months, hoping to provide you with awesome sounds, unique designs, inspiration, knowledge and relaxation (or procrastination, if you’re at work reading this).