Synthesis Essentials: All About Oscillators

Oscillators. The raw sound source that spawns the diverse range of tones and timbres spewed by all synthesizers. They come in different shapes and can be produced by a variety of techniques to make your imagination audible. If you consider the fact that all of the sounds we hear are vibrations in air, oscillators are creating synthetic vibrations that become sound once connected to a speaker. Instead of moving back and forth like a guitar string, the oscillator cycles between positive and negative voltages.

If these cycles take place between 20 and 20,000 times per second they are audible to the human ear. The rate of these fluctuations determines the frequency, or pitch of the tone, and this is tuned to produce the notes struck by the keys. We call one full fluctuation a cycle, or period, and refer to the shape that these oscillations take as a waveform. The shape of the oscillation determines the timbre or tone of the sound.

 Types Of Oscillator

Sine, Triangle, Sawtooth, and Pulse (or Square) are the four most commonly utilized synthesizer waveforms. Sine waves represent the pure tone of a single frequency, which is called the fundamental. The other waveforms have added harmonics or overtones that take place above the fundamental. This can add brightness, complexity and texture to the sound. Sawtooth waves are the most harmonically rich, because they have harmonics every integer above the fundamental. Therefore a sawtooth wave played at 100Hz will have harmonics at 200Hz, 300Hz, 400Hz and so on. Each successive harmonic descends in amplitude, or volume, by half and this cascade creates the descending sawtooth shape.

Read the rest on Ask.Audio here: https://ask.audio/articles/synthesis-essentials-all-about-oscillators

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Review: Soulsby Synthesizers Oscitron

The Oscitron from Soulsby Synthesizers is a lot of things. It’s their first Eurorack synthesizer product. It’s an 8-bit digital oscillator with wavetable sampling, selectable audio engine resolution, multiple filter types, scale quantization, portamento, bit reduction and preset memory. Amazingly, they managed to squeeze all this functionality into just 14HP. This is achieved through the clever use of two knobs that also function as buttons.

You Know I Got Soulsby

The top function knob has two menu rings, and pressing it toggles between the red and green menu sets. This selects the page of parameters that the bottom button will edit. Additionally the Oscitron has knobs to control fine tuning, pulse width, filter frequency, filter resonance, and phaser offset. It provides 1v/Octave CV inputs for pitch and filter cutoff frequency, as well as inputs for pulse width, filter resonance and phaser position. There is also a clock and audio input for sampling new waveforms.

I was pleased when I opened the box to see both a detailed manual, a quick reference card, plus a cute pair of mini wood cheeks. I really appreciate it when manufacturers make this kind of extra effort. I generally prefer hands-on manuals to PDFs and I’m a sucker for wood cheeks on synths. Another unexpected discovery in the box was a little 2HP module called the Uni-Five with its own reference card. I reached out to Paul Soulsby to ask him about the Uni-Five and he was happy to give me a thorough explanation.

Paul explains : “the reason for the Uni-Five module is partly because the Oscitron is digital and partly to do with Eurorack theory! Like the Atmegatron, it’s 8-bit digital and only recognises voltages between 0V – 5V. In fact, voltages outside of this range would cause damage, but luckily it has loads of protection against this. If anything is connected out of that range it’ll just clip it to either 5V or 0V.  There’s two approaches to deal with this in the Eurorack world, where anything between -10V and +10V is fair game. I can have on-board attenuation, but the issues with that are: What kind of attenuation do I provide? Bias, attenuation, both, and over what voltage range? Or I can say: better to handle all bias and attenuation myself, so I can customize it for my own system.”

He continues: “when I developed the module, I felt that user customization was more appropriate. However, when I got to beta testing, users kept wanting to put a bipolar LFO into the filter, to make it go wah-wah-wah(!) and found the negative part of the LFO cropped off. I decided it should have some biasing and attenuation for the most common situations (5V LFO and 8V envelope). So I had the option to redevelop the entire product (which would have increased the HP and would have needed all parts prototyped again), or create a separate module, which would be much quicker, cheaper, and simpler, and could also be used with other 5V modules. So that’s basically the option I went with!”

Check out the rest of the article here: https://ask.audio/articles/review-soulsby-synthesizers-oscitron

 

Synthesis Essentials: Know Your Filters

The filter is arguably the element of a synthesizer that does the most to define its character. Words like squelchybrassycreamygritty and so on are often used to describe their impact, and reading those adjectives in this context probably made you think of a few specific synths. Perusing the various offerings in both the fixed architecture and eurorack markets presents a perplexing plethora of jargon. To make matters worse, many of these terms overlap, as manufacturers will often use different names to describe the same feature. So what makes all these filters different and how does that affect the way a synthesizer will sound?

The Basics

First, let’s brush up on the basic filter types and attributes. The low pass (sometimes referred to as high cut) filter is the most common type of synthesizer filter. As its name suggests it allows low frequencies to pass through, which can be useful for taming an abrasive top end. High pass (or low cut) filters do the opposite, letting the high frequencies through while cutting out the more rumbly tones. Mix a high pass with a low pass and you get either a band pass or a notch filter, depending on how they are arranged. A band pass allows only a narrow band of the frequency spectrum to pass through while the rest is filtered out. Notch is the opposite, filtering out only a narrow band of the frequency spectrum. A coffee filter, on the other hand, separates the ground beans from your coffee (I threw that one in just to see if you were paying attention).

There is also the more rare and mysterious All Pass filter. If everything is allowed to pass through then what exactly is filtered? In this case the entire signal is passed through but shifted in phase and blended with the original signal. At the filter cutoff point the phase shift is ninety degrees. The resulting phase cancellation causes an effect that sounds similar to a phaser or flanger. Similarly, comb filtering, which is the term for the actual result of a phaser, flanger, or chorus, is caused by blending the original signal with a slightly delayed version of itself which creates a series of notches through phase cancellation. The length of the delay determines where in the frequency spectrum the notches occur. Varying the amount of the delay time is what creates the swishy jet plane effect.

The cutoff frequency is the point in the spectrum where the filtering takes effect. Resonance is an emphasis added through feedback at the cutoff frequency. Sometimes the filter resonance parameter is labelled as Q, standing for Quality. In some cases adding resonance causes a dip surrounding the resonant peak. Some filters are able to create enough feedback that they produce a tone without any input signal at high resonance settings. These are referred to as self oscillating filters because they can effectively function as sine wave oscillators.

The number of poles, or slope of a filter determines how steep or gradually material is filtered beyond the cutoff frequency. Each pole represents a reduction of six decibels per octave, so a four pole filter would have an attenuation of 24db per octave.

While most synth aficionados are familiar with the above types of filters, they are also aware how much a low pass filter can vary from synth to synth, or even between different versions of the same model. Now that we’re on the same page, let’s take a look at some of the different architectures used to create some of our favourite filters.

Read the rest here: https://ask.audio/articles/synthesis-essentials-know-your-filters

Just in: Case!

Case MontageFor the first time in October, I had to take my gear on a plane. The logistics of transporting my equipment proved more difficult to solve than I anticipated. My eclectic collection of gear was pretty awkward to accommodate. Any bags or cases large enough to accommodate all of my equipment were too big to be guaranteed approval as carry on luggage. If I had to risk checking in my luggage, I wanted to make sure I had a case that would protect my synths and samplers. I looked at a number of cases from a range of companies but couldn’t find anything really appropriate. Finally I decided to give Dinosaur Cases a call. Doug listened to my requirements and gave me a rough quote, as well as a couple other recommendations to try. The more I looked around, the more I realized how reasonable his quote was. Many of the available products were just as expensive or even more. Having a custom case made specifically for my gear had some pretty attractive advantages too.

Case InsideEarlier in the year I had been visualizing a stand for my Kraftzwerg so that it would sit closer to the MicroBrute and angled upwards for better ergonomics and access to the knobs. If I was paying to have a custom case made, maybe I could have my studio workflow improved too. I ran this by Doug, and while it would increase the cost it would certainly be possible, so I decided to go ahead with the case.

Case FinishedI’m quite happy with the results! The Dinos were able to make a tray with a hinged shelf that sits inside the lid of the case. When I get to the gig I just put the case on a stand or a table, open it up, plug in a few cables and I’m ready to go. If it sits too low I can use the case as a platform and save myself a lot of back ache from hunching over my equipment. In the studio it sits nicely on my desk and the raised back items are more accessible. Plus it looks really professional and dare I say sexy.

 

 

 

 

 

Maker Faire 2014 and a WCMA Nomination!

Maker Faire SpreadOn June 8th I performed Sonidos de Cuba at the Vancouver Mini Maker Faire. My wife was also showing off her Drift clothing and accessories (you can check out her stuff here). Previously I had used a laptop running Ableton Live with an Akai APC40, a Korg Electribe ES1mkII and my trumpet. This time I debuted my new live setup focused around the Elektron Octatrack. I’m also using an Arturia MicroBrute, MFB Kraftzwerg, Electo-Lobotomy Sonic Forest, Manastone Hank Drum and Trumpet. Changing my setup has caused the songs to evolve quite dramatically. I’m still playing back stems from each song on the album, but sequencing them on the Octatrack has changed the way they’re configured. The Octatrack is also sequencing the two synthesizers which imparts some great new life into the material. Continue reading “Maker Faire 2014 and a WCMA Nomination!”