What is an analog synthesizer, and how does it work?
The definition of a synthesizer is an electronic device that brings together many different manipulations (modules) of electronic signals, to produce sound.
There are two basic ways to create sounds you want on a synth:
- Using Additive synthesis (adding harmonic content)
- Using Subtractive synthesis (removing harmonic content with a filter)
Easy so far, right?
To take a step back before we continue, it’s important to understand that sound is created by the movement of molecules in the air or other substances in the form of waves.
We can describe the movement of air molecules in a couple of ways:
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Amplitude: measures how far out we push the molecules from their original position
- We generally use this word to describe how loud or intense a signal is
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Frequency: measures how many times the molecules return to their position within a specific amount of times
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One cycle is one Hertz (1 Hz). One thousand cycles in a second is one Kilohertz (1 kHz)
- The more cycles in a second, the higher the pitch!
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The sound on a synthesizer comes from an oscillator: a module that generates a repetitive electrical signal called a waveform. It is the synth’s raw sound source. Changing how quickly the signal repeats changes its pitch, while changing its shape changes its harmonic character, or timbre. Other modules then shape this signal before it reaches the speakers.
How does an oscillator produce waves?
Inside an analog synth’s oscillator, is an important component called a capacitor. Entertain the analogy that a capacitor is like a tiny, rechargeable battery.
The synth’s power supply pours steady DC current into the capacitor. The electrical voltage increases.
Once the capacitor is completely full, an electronic switch flips open and instantly dumps that electricity out.
This repeats. The switch closes and the capacitor fills up again. The constant fill-and-dump cycle happens hundreds or thousands of times every single second.
How is the shape of a waveform made?
The actual geometric shape of the wave depends entirely on how that capacitor fills up and empties:
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Triangle Wave: The capacitor fills up steadily at a slope, and then instead of dumping instantly, it empties at that exact same steady slope backward. This creates symmetrical triangles.
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Sawtooth Wave: The capacitor fills up at a steady, linear pace (sloping upward), and then instantly dumps all its energy at once (dropping straight down). If you draw this voltage movement on a graph, it looks exactly like the teeth of a saw.
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Square Wave: Instead of a slope, the circuit uses a comparator switch. The voltage is either instantly turned 100% "ON" or instantly flipped 100% "OFF," creating a blocky, square shape.
What are harmonics and overtones?
A musical sound can contain many frequencies at the same time. The lowest frequency is the fundamental, which we hear as the note’s pitch. Every frequency above it is an overtone. When those frequencies are whole-number multiples of the fundamental, they are called harmonics: the second harmonic vibrates twice as fast, the third harmonic three times as fast, and so on.
The mix and strength of these harmonics gives a waveform its tone, or timbre:
- Sine wave: contains only the fundamental, with no harmonics above it. This gives it the purest and smoothest sound.
- Triangle wave: contains only odd harmonics, which become quiet very quickly. It sounds soft and mellow.
- Square wave: also contains only odd harmonics, but they remain stronger than those of a triangle wave. It sounds hollow and buzzy.
- Sawtooth wave: contains both even and odd harmonics. Its dense harmonic content makes it sound bright and sharp.
The waveforms, of which we are manipulating in various ways using the myriad of tools on a synthesizer such as filters, effects, and more, is how the final generating sound is determined.
Many synthesizers have multiple oscillators, which allow you to combine and blend different waveforms at the same time, to create all sorts of interesting sounds!
Visuals from Soundfly
My current setup includes an Oberheim TEO-5 analog synthesizer, a Yamaha MG06X and a pair of iLoud Micro Monitors.
As well, I use a Yamaha 6-channel analog mixing console to combine audio from the synthesizer and other sources, control their levels and send one mixed output to my speakers.
It's pretty cool because it has a built-in SPX effects processor that provides six reverb and delay programs, so I can add spatial effects without routing the signal through a computer!
What are mixers and how do they work?
A mixer is a traffic controller for audio. Each instrument or microphone produces its own electrical signal. A mixer receives those signals on separate channels, lets you adjust each one and then combines them into a single mix that can be sent to speakers, headphones or a recorder.
Each signal follows a path through the mixer:
- Input: the sound source plugs into a channel. A microphone produces a weak signal that must be amplified by a preamp, while a synthesizer usually produces a stronger line-level signal.
- Gain: the gain control sets how much the incoming signal is amplified. It should be high enough to keep the sound clear, but not so high that the signal clips and distorts.
- Equalization: EQ controls make selected frequency ranges louder or quieter, changing the balance of bass and treble in the sound.
- Effects: the mixer can send a copy of the signal through an effect such as reverb or delay, then blend the processed sound back into the original.
- Channel level: each channel's level control determines how much of that source is included in the final mix.
- Mix bus and output: the mixer adds the channels together on an internal signal path called a bus, then sends the combined signal to its outputs.
What is gain staging?
Gain staging means setting the signal level correctly at every step of its path. A signal that is too quiet can reveal background noise when amplified later. A signal that is too loud can exceed what the electronics can represent, flattening the waveform and producing distortion called clipping.
What do reverb and delay do?
Reverb creates many closely spaced reflections that imitate how sound lingers in a room. Delay repeats the sound after a short period of time, producing distinct echoes. Both effects can make a dry electronic signal feel as though it exists in a physical space.
An analog mixer represents sound as continuously changing electrical voltage while it combines and adjusts signals. The Yamaha MG06X has six input channels: two mono microphone or line channels and two stereo line-input pairs. Its main stereo output carries the completed mix to my speakers.