Analog synthesizer

An analog synthesizer is a synthesizer that uses analog circuits and analog computer techniques to generate sound electronically.

Analog synthesizer circuit composition

A very common circuit component in analog synthesizers is the operational amplifier (op-amp), a kind of integrated circuit; most analog synthesizers contain many of them; earlier models were built using discrete transistors instead of integrated circuits. Another common component is a potentiometer (pot, or variable resistor), which is used to adjust the traits of the sound that is produced. Some common components that consist of multiple parts are low-pass filters and high-pass filters.

Pioneer synthesizers

Trautonium, 1928

The earliest synthesizers used a variety of valve and electro-mechanical technologies. While some electronic instruments were produced in bulk, such as the Ondioline, the Hammond organ, the Trautonium, many of these would not be considered synthesizers by the standards of later instruments. However, some individual studios and instruments certainly achieved a high level of sophistication, such as the Trautonium of Oskar Sala, the Electronium of Raymond Scott, and the ANS synthesizer of Evgeny Murzin.

First generation modular synthesizers

File:Music easel2.jpg

Buchla Music Easel

The ARP 2500.

Early analog synthesizers used technology derived from electronic analog computers and laboratory test equipment. They were generally "modular" synthesizers, consisting of a number of independent electronic modules connected by patch cables.

Synthesizer modules found in early analog synthesizers included:

• voltage-controlled oscillators
• voltage-controlled filters
• voltage-controlled amplifiers
• envelope generators
• low-frequency oscillators
• ring modulators
• reverb units
• sequencers
• sound mixers

Because many of these modules took input sound signals and processed them, an analog synthesizer could be used both as a sound-generating and sound-processing system.

Famous modular synthesizer manufacturers included Buchla & Associates, Moog Music, ARP Instruments, Inc., and Electronic Music Studios.

Moog established standards recognized worldwide for control interfacing on analog synthesizers, using a logarithmic 1-volt-per-octave pitch control and a separate pulse triggering signal. These control signals were routed using the same types of connectors and cables that were used for routing the synthesized sound signals.

A specialized form of analog synthesizer is the analog vocoder, based on equipment developed for speech synthesis. Vocoders are often used to make a sound that resembles a musical instrument talking or singing.

First generation all-in-one synthesizers

Later analog synthesizers used the same building blocks, but integrated them into single units, eliminating patch cords in favour of integrated signal routing systems. The most popular of these was the Minimoog.

Famous makers of all-in-one analog synthesizers included Moog, ARP, Roland, Korg and Yamaha. Because of the complexity of generating even a single note using analog synthesis, most synthesizers remained monophonic.

Second generation all-in-one synthesizers

A second generation of analog synthesizers emerged later, with limited polyphony, typically supporting four voices. Oberheim was a notable manufacturer of analog polyphonic synthesizers.

The Polymoog was an attempt to create a truly polyphonic analog synthesizer, with sound generation circuitry for every key on the keyboard. However, its architecture resembled an electronic organ more than a traditional analog synthesizer, and the Polymoog was not widely imitated.

Third generation all-in-one synthesizers

In 1978, the first microprocessor-controlled analog synthesizers were created by Sequential Circuits. These used microprocessors for system control and control voltage generation, including envelope trigger generation, but the main sound generating path remained analog. The MIDI interface standard was developed for these systems. This generation of synthesizers often featured six or eight voice polyphony. Also during this period, a number of analog/digital hybrid synthesizers were introduced, which replaced certain sound-producing functions with digital equivalents, for example the digital oscillators in synthesizers like the Korg DW-8000 (which played back PCM samples of various waveforms) and the Kawai K5 (waveforms constructed via additive synthesis).

With the falling cost of microprocessors, this architecture became the standard architecture for high-end analog synthesizers.

The fall and rebirth of analog synthesis

Analog synthesizers were mostly replaced by digital synthesizers and samplers over the middle to late 1980s. In the early 1990s however, musicians interested in producing electronic music, but without the budget for large digital systems, began to take an interest in the then cheap second hand analog equipment available. This led to an increase in demand for "retro" analog synthesizers towards the mid-1990s, as larger numbers of musicians also gradually rediscovered their qualities. Thus the sounds associated with analog synths became more prevalent once again. Fundamental differences between analog and digital technology mean some of the characteristics of analog synthesizers cannot be wholly replicated by samplers or digital synthesizers. This has led to increased demand for used units (such as the Roland TR-808 drum machine and Roland TB-303 bass synthesizer), the development of a variety of analog modeling synthesizers which emulate analog VCOs and VCFs using samples, software, or specialized digital circuitry, and the construction of new analog keyboard synths such as the Alesis Andromeda, the Prophet 08 and the Little Phatty, as well as some modular units.

The lapse of patents in recent years, such as for the Moog synthesizer transistor ladder filter, has led to a small resurgence in DIY or kit synthesizer modules, as well as an increase in the number of commercial companies selling analog modules. Reverse engineering has also revealed the secrets of some synthesizer components, such as those from ARP Instruments, Inc., which are believed by some to have been potted in epoxy cases to prevent inspection (although the official reason was to maintain temperature stability within the circuit to avoid drifting).

External links

• ARP synthesizer patents
• Modular Analog Synthesizers Return! - a discussion of modern modular equipment with links to major manufacturers.