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-\begin_body - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -begin{textblock*}{ -\backslash -paperwidth}(0mm,30mm) -\end_layout - -\begin_layout Plain Layout - - -\backslash -begin{center} -\end_layout - -\begin_layout Plain Layout - - -\backslash -includegraphics[width= -\backslash -paperwidth-400px]{graphics/logo} -\end_layout - -\begin_layout Plain Layout - - -\backslash -end{center} -\end_layout - -\begin_layout Plain Layout - - -\backslash -end{textblock*} -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout - - -\backslash -begin{textblock*}{ -\backslash -paperwidth}(30mm,235mm) -\end_layout - -\begin_layout Plain Layout - - -\backslash -noindent -\end_layout - -\begin_layout Plain Layout - -SAE Berlin -\backslash - -\backslash - -\end_layout - -\begin_layout Plain Layout - -Student Id: 18128 -\backslash - -\backslash - -\end_layout - -\begin_layout Plain Layout - -Course: AED412 -\backslash - -\backslash - -\end_layout - -\begin_layout Plain Layout - -Headinstructor: Boris Kummerer -\backslash - -\backslash - -\end_layout - -\begin_layout Plain Layout - -Berlin, Germany 2012 -\backslash - -\backslash - -\end_layout - -\begin_layout Plain Layout - - -\backslash -end{textblock*} -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -author{ -\end_layout - -\begin_layout Plain Layout - -by Karl Pannek -\end_layout - -\begin_layout Plain Layout - -} -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout - - -\backslash -title{ -\backslash -LARGE{Prototyping a Modular Analog Synthesizer}} -\end_layout - -\begin_layout Plain Layout - - -\backslash -maketitle{ } -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -pagenumbering{arabic} -\end_layout - -\begin_layout Plain Layout - - -\backslash -setcounter{page}{2} -\end_layout - -\begin_layout Plain Layout - - -\backslash -renewcommand -\backslash -cftpartdotsep{6.6} -\end_layout - -\begin_layout Plain Layout - - -\backslash -renewcommand -\backslash -cftchapdotsep{6.6} -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Chapter* -Table of Contents -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -renewcommand -\backslash -contentsname{} -\end_layout - -\begin_layout Plain Layout - - -\backslash -vspace*{-8.5em} -\end_layout - -\begin_layout Plain Layout - - -\backslash -tableofcontents -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Chapter -Introduction -\end_layout - -\begin_layout Section* -Motivation -\end_layout - -\begin_layout Standard -The project was inspired by the film -\emph on -moog -\emph default - -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp{Fjellestad:movie}} -\end_layout - -\end_inset - -, a documentary about Dr. - Robert Moog, electronic instrument pioneer and inventor. - Its goal is to convey an understanding of the inner workings of electronic - synthesizers and their components. - The reader is guided through the process of creating a small but functional - modular synthesizer setup that is fun to play and experiment with. - The intention was to investigate the possibilities and limits in designing - and building an analog sound device for someone, who had not been in contact - with analog synthesizers, let alone building electronics devices before. -\end_layout - -\begin_layout Section* -Chapter Overview -\end_layout - -\begin_layout Standard -The first chapter represents the research on the historical background of - analog synthesizers since the beginning of the twentieth century. - It was tried to outline important milestones in the historic development - from the first electronic sound generating devices until a point in time - when manufacturers of modular synthesizers have developed a profitable - market. -\end_layout - -\begin_layout Standard -Subsequently the most important concepts of subtractive synthesis are summarized. - A general overview over common sound generation and processing methods - is given, whereby all concepts are applicable to both analog and digital - synthesis. - In chapter three these concepts are taken one step further and discussed - in the context of electronic circuitry. - Lastly the process of building an electronic synthesizer prototype is described. -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status collapsed - -\begin_layout Plain Layout -The process of building the prototype includes working with an oscilloscope - to examine and verify the shape of various waveforms before and after modulatio -n. - -\end_layout - -\begin_layout Plain Layout -To make it playable with a keyboard, a MIDI input module is added. - It features an Arduino microprocessor to convert digital MIDI messages - into control voltage outputs that other modules can connect to. - It is the only digital component of the synthesizer, while tone generation - and processing are analog. - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard - -\end_layout - -\begin_layout Section* -A Personal Journey -\end_layout - -\begin_layout Standard -As a trained programmer and web application developer the field of electronic - engineering always seemed appealing to me. - Hence the assignment for a research paper during the audio engineering - course at SAE Institute seemed like a welcome opportunity to dive into - the realm of building electronic devices in the context of sound generation - and modification. -\end_layout - -\begin_layout Standard -The process of writing this paper has been an unexpectedly rewarding and - inspiring experience, pushing the boundaries of my own musical and technical - understanding. - Most notably the concepts of free composition - meaning allowing randomness - and therefore putting oneself in the position of reacting to a musical - system, influencing it in terms of tendencies, rather than controlling - it with a predetermed mindset - has been something that really changed - my perseption of musical creativity. - This for me seems much more attainable in the analog world, where electrical - components and signal chains can be brought to their tipping points, resulting - in an unpredictable outcome. - That is where sound exploration begins, which is a totally different experience - than knowing what will happen. - Virtual digital environments, which I was familiar with on the other hand, - generally seem to tend persuade the user to feel in control at all times. -\end_layout - -\begin_layout Chapter -Historic Evolution of the Synthesizer -\end_layout - -\begin_layout Section -Early Development Milestones -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status collapsed - -\begin_layout Plain Layout -Electric instruments at that time were developed primarily to imitate and - evolve the sounds of classical instruments and therefore satisfy traditional - ideas of musical writing -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~12]{Manning1985}} -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -Around 1900 american Thadedeus Cahill initiated a new era of music by inventing - a 200 ton machine known as the Dynamophone or Thelharmonium -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~19]{Humpert1987}} -\end_layout - -\end_inset - -. - It was an electrical sound generator, that produced alternating sine wave - shaped currents of different audio frequencies. - A modified electrical dynamo was used in conjunction with several specially - geared shafts and inductors to create the signals. - The Dynamophone could be played with a polyphonic keyboard and featured - special acoustic horns to convert the electrical vibrations into sound - -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~1]{Manning1985}} -\end_layout - -\end_inset - -. - The timbre of the instrument was shaped from fundamentals and overtones. - This is known as the principle of additive synthesis -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~730]{Bode1984}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Standard -In 1924 the russian inventor Leon Theremin created the Aetherophone, which - would later be known as the Theremin. - Unlike most electric instrument developed around that time, the Theremin - had no keyboard. - It was played merely by hand motion around two capacitive detecors, that - generated electrical fields. - These were affected by the electric capacity of the human body. - One of these detectors was a vertical rod to control dynamics and the other - a horizontal loop to change the pitch -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~3]{Manning1985}} -\end_layout - -\end_inset - -. - -\begin_inset Quotes eld -\end_inset - -The theatricality of its playing technique and the uniqueness of its sound - made the Theremin the most radical musical instrument innovation of the - early 20th century. -\begin_inset Quotes erd -\end_inset - - -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~6]{Dunn1992}} -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -Some organ-like precursors to the synthesizer were the Ondes Martenot and - the Trautonium, which were devised just a few years later. - The Ondes Martenot is one of the few early electric instruments, that are - still in concert- and theatre use in their original design today -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~20]{Humpert1987}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Standard -The Givelet (1929) was a commercially more successful instrument, since - it was designed as a cheap alternative to pipe organs. - These instruments were polyphonic and unified the concepts of the Pianola - - a self-playing piano, controlled by pre-punched tape - with electronic - sound genaration. - The ability to program electronic sounds should lead the way for future - devices such as the RCA synthesizer or computer music production in general. - However, the Givelet was about to take a back seat, when Laurens Hammond - published his Hammond Organ in 1935. - Its technical operation principle is reminiscent of the Dynamophone, since - it also involved rotating discs in a magnetic field -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~3]{Manning1985}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Standard -The german engineer Harald Bode contributed to the design of several new - instruments from the 1930's on, like the warbo formant organ (1937) or - later the Melochord (1949). - He was primarily interested in providing tools for a wide range of musicians, - which is why his contributions straddled between the two major design tradition -s of new sounds versus imitation of traditional ones. - He turned out to be one of central figures in the history of electronic - music, since he was also one of the primary engineers in establishing the - classic tape music studio in europe -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~9]{Dunn1992}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Standard -Bode was one of the first engineers to grasp the significance of the invention - of the solid state transistor for sound synthesis. - In an article published in 1961 he draws particular attention to the advanteges - of modular design. - -\begin_inset Quotes eld -\end_inset - -The versatility of transistor-based electronics made it possible to design - any number of devices which could be controlled by a common set of voltage - characteristics. -\begin_inset Quotes erd -\end_inset - - -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~117]{Manning1985}} -\end_layout - -\end_inset - -. - But it was not until the early 1960's that major advances in electronic - design took shape -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~19]{Dunn1992}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status open - -\begin_layout Plain Layout -Sakbutt (1948) Hugh LeCaine -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Section -The First Synthesizers -\end_layout - -\begin_layout Standard -In 1955 the laboratories of the Radio Corporation of America (RCA) introduced - a new and very advanced machine to the public named the Olson-Belar Sound - Synthesizer, later known as the RCA Mark I Music Synthesizer. - It combined many means of tone generation and sound modification known - at the time and is considered the first synthesizer. - Mark I was built with the specific intention of imitating traditional instrumen -t sounds and to reduce the costs of the production of popular music by replacing - musicians. - However, the machine proved unsuitable for its original intent and was - later used completely for electronic music experimentation and composition - -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~15-16]{Dunn1992}} -\end_layout - -\end_inset - -. - The synthesizer could not be played in the conventional sense in real time. - Instead musical information had to be pre programmed as punched holes in - a large paper tape. - Harry Olson and Herbert Belar produced an improved Mark II Synthesizer - in 1957, which the nickname -\emph on -Victor -\emph default - was given -\emph on - -\emph default - -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp{Bear:website}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Standard -Around the same time the outstanding guitarist and inventor Les Paul became - famous with his multitrack guitar recordings. - He stimulated many innovators not only with the success of his multitrack - recorder, but also with his methods of electronic sound processing. - Harald Bode was so impressed and inspired by his work, that he built a - system consisting of a number of electronic modules for sound modification - in late 1959 through 1960. - His system featured ring modulator devices, envelope followers and generators, - voltage-controlled amplifiers, filters, mixers and others -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~733]{Bode1984}} -\end_layout - -\end_inset - -. - The modular concept of his device had proven attractive due to its versatility - and predicted the more powerful modular synthesizers that emerged in the - early 1960's -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~20]{Dunn1992}} -\end_layout - -\end_inset - -. - -\end_layout - -\begin_layout Standard -In 1963 Robert Moog, a passionate inventor from Ithaca, New York, was selling - kits of transistorized Theremins -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~20]{Dunn1992}} -\end_layout - -\end_inset - -. - As he states in the movie about him -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp{Fjellestad:movie}} -\end_layout - -\end_inset - -, he had been completely obsessed with building and later designing Theremins - since the age of 14. - A year later he built a transistor based voltage-controlled oscillator - and amplifier for the composer Herbert Deutsch. - This led moog to the presentation of a paper entitled -\emph on -Voltage-Controlled Electronic Music Modules -\emph default - at the sixteenth annual convention of the Audio Engineering Society, which - had stimulated widespread interest -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~117-118]{Manning1985}} -\end_layout - -\end_inset - -. - -\end_layout - -\begin_layout Standard -Similar developments had been taking place at the west coast of the united - states. - Morton Subotnick and Ramon Sender started their carreer in electronic music - experimentation, and became increasingly dissatisfied with the severe limitatio -ns of traditional equipment at the San Francisco Tape Music Center, where - they were working. - They sought out to hire a competent engineer and met Donald Buchla -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~117-118]{Manning1985}, -\backslash -citealp[p.~22]{Dunn1992}} -\end_layout - -\end_inset - -. - Their discussions resulted in the concept of a modular voltage-controlled - system. - Buchla's design approach differed significantly from Moog. - He rejected the idea of a synthesizing familiar sounds and resisted the - word -\emph on -synthesizer -\emph default - ever since. - It seemed much more interesting to emphasize new timbral possibilities - and stress the complexity that could arise from randomness. - At the same time Buchla was fascinated with designing control devices other - than the standard keyboard, which Moog decided to use for playing -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~20]{Dunn1992}} -\end_layout - -\end_inset - -. - -\end_layout - -\begin_layout Standard -In 1966 Bob Moogs first production model was available from the business - R.A. - Moog Co. - that he had founded -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~20]{Dunn1992}} -\end_layout - -\end_inset - -. - At this time Walter Carlos, an audio engineer from New York who adviced - Bob Moog while perfecting his system, worked with Benjamin Folkman to produce - an album of titles by Johann Sebastian Bach interpreted only with Moog - synthesizers. - With the title -\emph on -Switched-on Bach -\emph default - they demonstrated the performance of the system so convincingly, that they - hit the popmusic charts and sold a million LP's -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~45]{Ruschkowski1990}} -\end_layout - -\end_inset - -. - -\end_layout - -\begin_layout Standard -By the end of the decade two other manufactrurers entered the market: ARP - in America and EMS Ltd. - in England. - They had become major rivals for Moog and Buchla. - Synthesizer production was dominated by these four companies for several - years, whereby each firm struggled for a major share of a highly lucrative, - rapidly expanding market -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~118]{Manning1985}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Chapter -Theory of Subtractive Synthesis -\end_layout - -\begin_layout Section -Sources -\end_layout - -\begin_layout Standard -Acoustic events can generally be divided in two groups: noises and tones. - Whereas tones - as opposed to noise - are classified as sound waves, that - oscillate in a periodic manner. - However this is only a theoretical classification, since most natural sounds - are a combination of the two -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~52]{Ruschkowski1990}} -\end_layout - -\end_inset - -. - -\end_layout - -\begin_layout Subsection -Wave Oscillation -\end_layout - -\begin_layout Standard -At the root of every artificial tone generating system there is an element - that produces an oscillation. - This element is mostly described as the oscillator, which represents the - very source of what can be heard eventually. - The oscillator produces a periodic wave, that moves between an amplitude-minima - and -maxima. - Its waveform (shape of the wave) determines the overtone structure and - therefore the timbre of this basic source sound. - Oscillators often provide several waveforms between which it is possible - to switch back and forth. - The pitch of the output signal is defined by the frequency of the wave - and must oscillate between 20Hz and 20kHz in order for it to be audible - to humans -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~124]{Friesecke2007}} -\end_layout - -\end_inset - -. - The output signal can later be processed and modulated in several ways. -\end_layout - -\begin_layout Standard -Oscillators that swing at an infrasonic frequency - meaning a frequency - so low, that it is not hearable anymore - are called low frequency oscillators - (LFO). - They are used to control parameters of different components of the synthesizer - periodically. - For example to influence the pitch of another oscillator to get a vibrato - - or the amplitude to get a tremolo effect. - Some oscillators frequencies range from very low to very high, in which - case a distinction between oscillator and LFO is unnecessary. -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status collapsed - -\begin_layout Plain Layout -Difference between poly and monophonic synthesis (voices, mono: store last - note value) Voices -\end_layout - -\begin_layout Plain Layout -unison -\end_layout - -\begin_layout Plain Layout -sync -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Subsubsection -Characteristics of Common Waveforms -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -sine The most basic waveform is the sine wave. - It contains no overtones at all and sounds round and dull. -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -sawtooth The sawtooth, also known as saw or ramp waveform sounds very bright, - sometimes described as trompet-like -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~49]{Anwander2011}} -\end_layout - -\end_inset - -. - It consist of a complete series of harmonics and is therefore well suited - for subtractive synthesis. - There are two types of sawtooth waves: rising and descending. - -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -triangle Composed of only odd harmonics, the triangle wave has a much softer, - flute-like sound. -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -square Also known as rectangle, -\begin_inset Note Note -status open - -\begin_layout Plain Layout -clearify difference to triangle -\end_layout - -\end_inset - - the square wave also consists of odd harmonics only. - Its timbre reminds of woodwind instruments -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~55]{Ruschkowski1990}} -\end_layout - -\end_inset - -. - A true square wave has a 50 % duty cycle - equal high and low periods. - However, oscillators often feature a pulse width parameter, trough which - the high-low time ratio can be accessed. - This has a distinct influence on the wave's timbre. - In this case, the square becomes a pulse waveform. -\end_layout - -\begin_layout Subsection -Noise Generation -\end_layout - -\begin_layout Standard -A different approach on the creation of source audio material is resembled - by noise generators, which generate random non-periodic frequencies. - Therefore the signal contains no tonal information. -\end_layout - -\begin_layout Subsubsection -Noise Types -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -white Equal power density in any band of the frequency spectrum -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -pink Power density decreases by 3dB per octave; also referred to as 1/f - noise -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -brown Power density decreases by 6dB per octave; also referred to as 1/f -\begin_inset script superscript - -\begin_layout Plain Layout -2 -\end_layout - -\end_inset - -noise -\end_layout - -\begin_layout Standard -The names of these noise types were derived from the spectral distribution - of the correspondingly colored light -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~155]{Friesecke2007}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Subsection -Triggering Notes -\end_layout - -\begin_layout Standard -In order to use the previously discussed signal generators in a musical - context, it is necessary to cut off their stationary signals when no note - is being played. - This is accomplished by routing the output signal of the generator to an - amplifier and providing it with a gate signal. - The source of the gate signal can be a keyboard or a sequencer, which would - also send a pitch value to the oscillator to set its frequency -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~36]{Anwander2011}} -\end_layout - -\end_inset - -. -\end_layout - -\begin_layout Section -Signal Processing -\end_layout - -\begin_layout Standard -In their raw shape the mentioned source signals sound rather underwhelming, - since they produce fixed timbres lacking of distinctive qualities -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~49]{Manning1985}} -\end_layout - -\end_inset - -. - To get a more interesting sound, the signal can be manipulated in acoustic - colour or dynamics by one or more processing units. -\end_layout - -\begin_layout Subsection -Dynamic Envelopes -\end_layout - -\begin_layout Standard -The most important component responsible for shaping the dynamic structure - of a note is the envelope. - It is triggered by the the gate on/off signal and outputs a control signal - that fades between the different state phases of a note. - The rapidity of these changes is adjusted by parameters, that represent - these states. - Its output signal can be used to control an amplifier and therefore shape - the dynamic structure of the note. - The most common envelope type is the ADSR, which stands for attack, decay, - sustain, release. - -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -Attack sets how long the envelope signal rises after a note was triggered -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -Decay sets how long it takes for the envelope signal to drop from its maximum - to the sustain level after the attack phase was completed -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -Sustain sets the output level for the time period after the decay phase - and before the gate signal was terminated -\end_layout - -\begin_layout Labeling -\labelwidthstring 00.00.0000 -Release sets the length of the fade out after the note has endede -\end_layout - -\begin_layout Standard -Envelopes can also be used to control other parameters, for example the - cutoff frequency of a filter (see chapter -\begin_inset CommandInset ref -LatexCommand ref -reference "sub:filters" - -\end_inset - -). - -\end_layout - -\begin_layout Subsection -Filtering -\end_layout - -\begin_layout Standard -\begin_inset CommandInset label -LatexCommand label -name "sub:filters" - -\end_inset - - The filter is the processing component responsible for the sound changes, - that people associate with -\emph on -the typical synthesizer sound -\emph default - -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~53]{Anwander2011}} -\end_layout - -\end_inset - -. - They remove a spectrum of frequencies from their input signal above or - below the cutoff frequency and are often used in conjunction with an envelope - or LFO modulation on the cutoff. - This cutoff frequency is an important parameter determining the frequency - at which the signal begins to be attenuated. - The slew rate sets the slope of the filter - meaning how abrubt frequencies - are being cut. -\end_layout - -\begin_layout Standard -Filters can generally be devided into two categories: Low pass and high - pass filters (also called high cut and low cut). - To get a bandpass filter, low- and high pass are connected in series. - When connected parallely, they become a bandstop or bandreject filter. - Lastly the allpass filter should be mentioned, which does not change the - frequency spectrum but merely influences the phase of the signal around - its cutoff -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~55]{Anwander2011}} -\end_layout - -\end_inset - -. - -\begin_inset Note Note -status open - -\begin_layout Plain Layout -COVER RESONANCE!!! -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Section -Controllers -\end_layout - -\begin_layout Standard -Controllers can be characterized by the way of how humans interact with - them and how their output signal is applied in controlling other components - of the system -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -citetext{ -\backslash -citealp[p.~9]{Hutchins1975}} -\end_layout - -\end_inset - -. - A keyboard for example is a manual controller, since it is the movement - of the players fingers which are translated into a voltage or control value - and then used to control pitch and amplitude of a note. - The same applies for rotary knobs and faders or touch sensitive surfaces. - -\end_layout - -\begin_layout Standard -Sequencers on the other hand are programmable controllers. - They are not dependend upon a manual interaction except for their programming - and activation. - -\end_layout - -\begin_layout Section -The Modular Approach -\end_layout - -\begin_layout Standard -A modular synthesizer is an electronic instrument, where sound generators, - processors and control facilities are presented in separate independent - entities called modules. - These modules are not wired in a preconceived way, but connected together - with patchchords. - The second essential aspect is the concept of intermodular controllability, - with which modules may modulate or regulate the behaviour of other modules. - -\end_layout - -\begin_layout Chapter -Analog Synthesis -\end_layout - -\begin_layout Section -General -\end_layout - -\begin_layout Standard -Voltage -\end_layout - -\begin_layout Standard -Control Voltage Audio Signal -\end_layout - -\begin_layout Standard -Current -\end_layout - -\begin_layout Standard -Rotary Knob -\end_layout - -\begin_layout Section -Modules -\end_layout - -\begin_layout Standard -intermodular stuff like buffering -\end_layout - -\begin_layout Subsection -Oscillator -\end_layout - -\begin_layout Subsection -Filter -\end_layout - -\begin_layout Subsection -Amplifier -\end_layout - -\begin_layout Subsection -Envelope Generator -\end_layout - -\begin_layout Subsection -Output -\end_layout - -\begin_layout Chapter -Building a Modular Synthesizer -\end_layout - -\begin_layout Section -Introduction -\end_layout - -\begin_layout Standard -It is relatively easy to find circuits to construct simple oscillators and - filters based on the fairly comprehensible concepts of resonant circuits - and RC blocks. - Some of these concepts will be covered later. - However, as their flexibility and capabilities increase (e.g. - controlling the frequency of an oscillator with 1 volt per octave), the - circuits tend to get exceedingly complex, requiring solid expertise in - electronics. - -\end_layout - -\begin_layout Standard -This is why it was decided to switch to the usage of pre-designed, professionall -y manufactured circuit boards for this project as opposed to elaborating - all the circuits on perf boards as originally intended. - This made the goal of intermodular controllability attainable more easyily. - The downside of this approach are higher costs for boards and parts. - However, the quality of the end-product is impressing. - Also the time saving using this strategy is not to be underestimated. -\end_layout - -\begin_layout Standard -During the research phase of this project the author found out about a modular - synthesizer building workshop taking place in berlin monthly. - It is organized by a spanish collective from barcelona called -\emph on -befaco -\emph default - (http://befaco.org/). - At the workshop it was possible to acquire various module kits containing - all necessary parts and also receive tips and support while assembling - them. - -\end_layout - -\begin_layout Standard -Since the budget for this project was limited, it was tried to arrange a - smaller setup that would still offer lots of sound design possibilities. -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status collapsed - -\begin_layout Plain Layout -Befaco, help, how well it is documented is important, why the filter was - chosen, limited budget -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Section -Formats and Interfaces -\end_layout - -\begin_layout Standard -There are several formats for module sizes, power supply plugs or patchchord - connectors which emerged out of the production lines of various module - manufacturers. - For example Doepfer's modules are only compatible with their EuroRack cases, - with a height of 128.5mm. - These EuroRack modules use jack connectors for patching. - A different size format often used in the DIY modular synth scene is the - one the serge synthesizers use. - They use banana jack connectors instead of mini jack for patching, which - have the possibility of stacking banana connectors on top of each other - and splitting the signal without having to use a multiplier module. - For this project a combination was chosen: The modules are EuroRack size, - but using banana plugs. -\end_layout - -\begin_layout Standard -For tuned modules it is important to consider whether they use a volts per - octave or volts per hertz characteristic. -\end_layout - -\begin_layout Standard -Audio Signals ±5Volts -\end_layout - -\begin_layout Standard -Buffering 1:10 impedance ratio -\end_layout - -\begin_layout Section -Building and Testing -\end_layout - -\begin_layout Standard -To get started with building electronic equipment, one has to obtain some - tools first. - This includes a soldering iron - best with adjustable temperature, a role - of quality soldering tin, a desoldering pump and pliers for cutting and - bending wire. - -\end_layout - -\begin_layout Standard -Soldering is a process of mounting electronic parts onto a circuit board - by heating up board and component and then melting the soldering tin into - the joint. - A good temperature for the soldering iron is between 300° and 350° celsius. - The iron should not be pressed onto the joint for too long, because there - is a risk of destroying the component if it is sensitive to heat. -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status collapsed - -\begin_layout Plain Layout -Research beginnings - Easy oscillation circuits. - easy filters. - how voltage controlled is the problem. - How it had been decided not to design all circuits self, but instead use - predesigned circuit boards in order to be able to get tuning stability - and volt-per-octave possibilities. -\end_layout - -\begin_layout Plain Layout -It had been understood how designing circuits requires years of work and - experience. -\end_layout - -\begin_layout Plain Layout -Module decicion, Getting the Circuit boards, Soldering, Getting Parts, General - about parts (capacitors and resistors) -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -Oscilloscope, Multimeter, Tracking faults, measuring -\end_layout - -\begin_layout Section -Power Supply and Case -\end_layout - -\begin_layout Standard -For the power unit a universal power supply circuit was chosen from an audio - circuit technology book (Sontheimer, 2004, p. - 74) and mounted onto a perf board. - Instead of the 7815 and 7915 voltage regulator ICs the 7812 and 7912 were - used in order to get a ±12 volt power supply with a center tap for the - ground. - The modules can be connected to the four male 16-pin flat ribbon connectors, - that were added to make the power supply compliant to the EuroRack standard. - Another possibility would be to make a flying bus board by attaching those - connectors to a flat ribbon cable that lies in the case. - Or even just fix female connectors to the cable and plug them directly - into the modules. - Additionally it is planned to add an IEC socket and a power switch to it - for more comfortable on and off switching and more steady starting current. -\end_layout - -\begin_layout Standard -The case is a simple rack constructed from a few pieces of wood that are - held together by 19 inch rails equipped with thread rails to fasten the - modules. -\end_layout - -\begin_layout Standard -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -pagebreak -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Section -Frontpanels -\end_layout - -\begin_layout Standard -\begin_inset Wrap figure -lines 0 -placement R -overhang 3in -width "22text%" -status open - -\begin_layout Plain Layout -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -vspace*{-2em} -\end_layout - -\begin_layout Plain Layout - - -\backslash -begin{center} -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename graphics/output-module-panel.pdf - scale 60 - -\end_inset - - -\end_layout - -\begin_layout Plain Layout -\begin_inset Caption - -\begin_layout Plain Layout -Output module template -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout -\begin_inset ERT -status open - -\begin_layout Plain Layout - - -\backslash -end{center} -\end_layout - -\begin_layout Plain Layout - - -\backslash -vspace*{-2em} -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -The panels for all modules were made from pre-cut aluminum plates with a - white varnish. - The labels for knobs and banana sockets are printed on the plates with - a method, that is similar to homemade circuit board etching. - A mirror-inverted label template is printed onto a piece of high gloss - paper for inkjet printers - but with a laser printer. - It is cut and placed face down onto the upper side of the panel. - By thoroughly pressing down a hot flat iron (for ironing clothes) onto - the panel for a few minutes, the toner cartridge particles move to the - panel. - The paper residues need to be removed by placing the panel in some water - and rubbing them off with a sponge. - Afterwards the panel is sealed with transparent lacquer. - Once the panel is dried, the holes for the knobs, switches, etc. - can be prepunched and drilled. - Lastly all borholes are deburred. - -\begin_inset Note Note -status open - -\begin_layout Plain Layout -foto vom frontpanel ohne stecker -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Section -BF-22 Filter -\end_layout - -\begin_layout Standard -This module is an extended copy of the filter from the legendary Korg MS-20 - and is based upon the principle of the sallen and key filter. - It combines two linkable filter stages in one module. - Each stage features cutoff and frequency knobs, as well as several voltage - control inputs for cutoff frequency and resonance, whereas the cutoff frequency - input can be attenuated and inverted with one knob representing modulation - depth (labeled: ×-1 ... - 0 ... - ×1). - The HP/LP switch determines, if the filter is used in high pass or low - pass mode. - -\end_layout - -\begin_layout Standard -When turning resonance up, at one point the filter begins to self-resonate - at the given cutoff frequency, which means that the filter can also be - used as an oscillator. - Therefore a volts per octave input for the cutoff control voltage was added, - to be able to control the oscillating frequency in a musical context. - A look at the oscilloscope shows a sine like waveform with few overtones. - Turning the resonance to the maximum, the filter goes into distortion and - the wave becomes more square causing the sound to get more rough. - The amount of distortion is visually represented by a red LED. -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status open - -\begin_layout Plain Layout -beispiel patch mit foto und beschreibung -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Section -Midi Input -\end_layout - -\begin_layout Standard -Note Source -\end_layout - -\begin_layout Section -Output -\end_layout - -\begin_layout Chapter -Conclusion -\end_layout - -\begin_layout Standard -describe the journey, discribe the difference and natururality of analog - sound as opposed to the digital, which i only knew before. -\end_layout - -\begin_layout Standard -tweaking knobs to borders where the outcome is on a threshold resulting - in unpredictable patterns. - -\end_layout - -\begin_layout Standard -Thanks to Eddi, Derek, Befaco, Richard, David -\end_layout - -\begin_layout Section* -List of figures -\end_layout - -\begin_layout Standard -\begin_inset CommandInset bibtex -LatexCommand bibtex -bibfiles "synth_bibliography" -options "karl-second4" - -\end_inset - - -\end_layout - -\begin_layout Chapter* -Declaration of academic honesty -\end_layout - -\begin_layout Standard -I hereby declare that in the attached submission I have not presented anyone - else’s work, in whole or in part, as my own using only the admitted resources. - Where I have taken advantage of the work of others, I have given full acknowled -gement. -\end_layout - -\begin_layout Standard -My signature below constitutes my pledge that all of the writing is my own - work, with the exception of those portions which are properly documented. - -\end_layout - -\begin_layout Chapter* -Appendix -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status open - -\begin_layout Plain Layout -urs hegemann -\end_layout - -\begin_layout Plain Layout -future audio workshop - cycle oder circle synthe -\end_layout - -\end_inset - - -\end_layout - -\end_body -\end_document diff --git a/facharbeit.lyx b/facharbeit.lyx index 5804d6d..a6f4af3 100644 --- a/facharbeit.lyx +++ b/facharbeit.lyx @@ -360,7 +360,7 @@ tableofcontents \end_layout \begin_layout Chapter -Introduction +Preface \end_layout \begin_layout Section*