From 43e636fc244aef5a644fc3e50534d013ed34b571 Mon Sep 17 00:00:00 2001 From: Logsol Date: Sun, 31 Mar 2013 18:26:48 +0200 Subject: [PATCH] extended introduction and conclusion --- #facharbeit.lyx# | 2907 ++++++++++++++++++++++++ facharbeit.lyx | 432 +++- graphics/Sallen-Key-Filter-Lowpass.png | Bin 0 -> 29820 bytes graphics/Sallen-Key_Lowpass.svg | 613 +++++ synth_bibliography.bib | 12 +- 5 files changed, 3906 insertions(+), 58 deletions(-) create mode 100644 #facharbeit.lyx# create mode 100644 graphics/Sallen-Key-Filter-Lowpass.png create mode 100644 graphics/Sallen-Key_Lowpass.svg diff --git a/#facharbeit.lyx# b/#facharbeit.lyx# new file mode 100644 index 0000000..e14f752 --- /dev/null +++ b/#facharbeit.lyx# @@ -0,0 +1,2907 @@ +#LyX 2.0 created this file. 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+\suppress_date false +\use_refstyle 0 +\index Index +\shortcut idx +\color #008000 +\end_index +\paperwidth 11in +\paperheight 8.5in +\leftmargin 3.5cm +\topmargin 3cm +\rightmargin 2cm +\bottommargin 3cm +\secnumdepth 2 +\tocdepth 2 +\paragraph_separation indent +\paragraph_indentation default +\quotes_language english +\papercolumns 1 +\papersides 1 +\paperpagestyle empty +\tracking_changes false +\output_changes false +\html_math_output 0 +\html_css_as_file 0 +\html_be_strict false +\end_header + +\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 +Preface +\end_layout + +\begin_layout Section* +Introduction +\end_layout + +\begin_layout Standard +This paper constitutes an attempt to summarize the most important facts + and information on the topic of analog, modular synthesizers. + The range of discussed subjects involves a series of various perspectives, + including historical, theoretical, electronic and practical viewpoints. + +\end_layout + +\begin_layout Standard +Its goal is to convey an understanding of the inner workings of electronic + synthesizers and their components. + Moreover 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. + The project was inspired by the film +\emph on +moog +\emph default + +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite{Fjellestad:movie} +\end_layout + +\end_inset + +, a documentary about Dr. + Robert Moog, electronic instrument pioneer and inventor. + +\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 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 +cite[p.~12]{Manning1985} +\end_layout + +\end_inset + + +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Standard +Around 1900 american Thaddeus 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 +cite[p.~19]{Humpert1987} +\end_layout + +\end_inset + +. + Working against incredible technical difficulties, he succeeded to create + 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 +cite[p.~1]{Manning1985} +\end_layout + +\end_inset + +. + The timbre of the instrument was manually shaped from fundamentals and + overtones. + This is known as the principle of additive synthesis +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~730]{Bode1984} +\end_layout + +\end_inset + +. +\end_layout + +\begin_layout Standard +\begin_inset Wrap figure +lines 0 +placement O +overhang 0in +width "4.5cm" +status collapsed + +\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/theremin.jpg + display false + width 4.5cm + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Caption + +\begin_layout Plain Layout +Leon Theremin performing the Aetherophone +\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 +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 +cite[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 +cite[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 +cite[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 +cite[p.~3]{Manning1985} +\end_layout + +\end_inset + +. +\end_layout + +\begin_layout Standard +\begin_inset Wrap figure +lines 0 +placement O +overhang 0in +width "4.5cm" +status collapsed + +\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/bode-melochord.jpg + display false + width 4.5cm + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Caption + +\begin_layout Plain Layout +Harald Bode tuning his first Melochord +\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 + +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 +cite[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 +cite[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 +cite[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 +cite[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 +cite{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 +cite[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 +cite[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 +cite[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 +cite{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 +cite[p.~117-118]{Manning1985} +\end_layout + +\end_inset + +. + +\end_layout + +\begin_layout Standard +\begin_inset Wrap figure +lines 0 +placement I +overhang 0in +width "5cm" +status collapsed + +\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/buchla.jpg + display false + width 5cm + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Caption + +\begin_layout Plain Layout +Donald Buchla with a Series 100 system in the 1960's +\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 + + 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 +cite[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 +cite[p.~20]{Dunn1992} +\end_layout + +\end_inset + +. + +\end_layout + +\begin_layout Standard +\begin_inset Wrap figure +lines 0 +placement O +overhang 0in +width "5cm" +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/switched-on-bach.jpg + display false + width 5cm + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Caption + +\begin_layout Plain Layout + +\emph on +Switched-On Bach +\emph default + LP artwork +\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 + + 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 +cite[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 +cite[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 +cite[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 +cite[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 +cite[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 +cite[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 +cite[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 +cite[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 +cite[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 +cite[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 +\begin_inset CommandInset label +LatexCommand label +name "sub:filters" + +\end_inset + + +\end_layout + +\begin_layout Standard +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 +cite[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 +cite[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 +cite[Ch.~1A, p.~5]{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 +In the context of audio electronics it is important to be know that sound + signals are nothing but currents. + +\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 Standard +intermodular stuff like buffering +\end_layout + +\begin_layout Section +Modules +\end_layout + +\begin_layout Subsection +Oscillator +\begin_inset CommandInset label +LatexCommand label +name "sub:electronic-oscillator" + +\end_inset + + +\end_layout + +\begin_layout Subsubsection +Natural Resonance +\end_layout + +\begin_layout Standard +The most basic form of an oscillator circuit producing a sawtooth signal + can be realized with just a few parts. + A current charges a capacitor at a certain rate. + Between the electrodes of the capacitor a voltage potential rises. + The voltage is constantly compared with a reference voltage by a detector + (Schmitt trigger). + Once it reaches the predefined threshold, an electronic switch (transistor) + is activated. + This switch short-circuits the capacitor and discharges it, causing the + output voltage to drop back to its initial potential. + This is happening continiously, wheras the rate of the repetition determines + the frequency of the generated signal. + +\end_layout + +\begin_layout Standard +\begin_inset Float figure +wide false +sideways false +status collapsed + +\begin_layout Plain Layout +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +begin{center} +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Graphics + filename graphics/sawtooth-oscillator-circuit.png + display false + width 80text% + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +end{center} +\end_layout + +\end_inset + + +\begin_inset Caption + +\begin_layout Plain Layout +Abstract circuit scheme of a basic sawtooth oscillator +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Plain Layout + +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Standard +To get a triangle shaped output signal, the current source can be reversed + in response to the detector +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[Ch.~5B, p.~3]{Hutchins1975} +\end_layout + +\end_inset + +. +\end_layout + +\begin_layout Standard +\begin_inset Float figure +wide false +sideways false +status collapsed + +\begin_layout Plain Layout +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +begin{center} +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Graphics + filename graphics/triangle-oscillator-circuit.png + display false + width 80text% + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +end{center} +\end_layout + +\end_inset + + +\begin_inset Caption + +\begin_layout Plain Layout +Circuit scheme of a simple triangle oscillator +\end_layout + +\end_inset + + +\end_layout + +\end_inset + + +\end_layout + +\begin_layout Standard +Either of these two waveforms can be waveshaped into to other common basic + waveforms. + All required waveshaping methods are fairly simple and their accuracy is + sufficient for musical purposes. + The sine wave is an exception, because there is no simple electronic method + of creating a pure sine wave. + What is generally used is a rounded triangle, which gives at least 1 % + of harmonic distortion. + In order to get a purer sine wave, the harmonics can be filtered out with + a VCF following in the signal chain +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[Ch.~5B, p.~3-4]{Hutchins1975} +\end_layout + +\end_inset + +. +\end_layout + +\begin_layout Subsubsection +Voltage Control +\end_layout + +\begin_layout Standard +How fast the capacitor is charged is determined by the intensity of the + current that it is being charged with. + This current is being extracted from a voltage, which of course can be + a control voltage. +\end_layout + +\begin_layout Standard +However, creating a stable VCO design presents one of the toughest challenges + for musical engineers, because the human ear is extremely sensitive to + pitch changes. + Also compositional processes like multitrack recording plainly reveal errors + in pitch relationships +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[Ch.~5B, p.~1]{Hutchins1975} +\end_layout + +\end_inset + +. + The voltage to pitch distribution curve of an oscillator is determined + by its exponential response to the voltage at its CV input. + In a volt per octave system an increase by 1 volt at the input must result + in a doubling of the oscillation frequency at the output. + Thus octave purity is achieved. + +\end_layout + +\begin_layout Standard +A major issue that oscillator designers have to face are temperature influenced + variations of the electrical parameters of the system, causing the oscillator + pitch to drift when temperature changes occur. + To overcome this problem some kind of temperature compensation should be + implemented. +\end_layout + +\begin_layout Subsection +Filter +\begin_inset CommandInset label +LatexCommand label +name "sub:electronic-filter" + +\end_inset + + +\end_layout + +\begin_layout Subsubsection +Passive Filter +\end_layout + +\begin_layout Standard +Filter circuits are generally based upon the fact that the transfer of alternati +ng currents through a capacitor becomes increasingly weak below a certain + frequency. + A signal simply passed through a capacitor resembles a high pass filter. + If the capacitor is connected to the ground the high frequencies are short + circuited and low frequencies remain in the signal path. + This is referred to as a resistor-capacitor (RC) element. + This simple circuit represents a passive, first-order butterworth filter + with a roll-off of 6 dB per octave. + +\begin_inset Note Note +status collapsed + +\begin_layout Plain Layout + The moog filter for example concatenates four of these RC elements in a + row and regulates the resistor values +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~57]{Anwander2011} +\end_layout + +\end_inset + +. + +\end_layout + +\end_inset + + To increase the slope of the filter multiple RC elements can be connected + in series +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~57]{Anwander2011} +\end_layout + +\end_inset + +. + +\end_layout + +\begin_layout Standard +Nevertheless this poses some disadvantages, because the filter stages influence + each other. + The resistor of the first filter affects the resistance of the second. + This can be dealt with by designing the second filter to have a much higher + impedance. + Unfortunately a high impedance circuit is much more prone to interferences + and signal noise +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~97]{Sontheimer2004} +\end_layout + +\end_inset + +. +\end_layout + +\begin_layout Subsubsection +Active Filter +\end_layout + +\begin_layout Standard +\begin_inset Wrap figure +lines 0 +placement O +overhang 0in +width "5.5cm" +status collapsed + +\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/Sallen-Key-Filter-Lowpass.png + display false + width 5.5cm + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Caption + +\begin_layout Plain Layout +Active Sallen-Key low pass filter circuit scheme +\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 + + A better and more flexible solution is the usage of an active filter design, + like the Sallen-Key filter. + This is a common second-order filter, which is applicable as a low or high + pass, whereby only resistors and capacitors have to be swapped +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~97]{Sontheimer2004} +\end_layout + +\end_inset + +. + Resistor +\begin_inset script superscript + +\begin_layout Plain Layout +2 +\end_layout + +\end_inset + + and capacitor +\begin_inset script superscript + +\begin_layout Plain Layout +2 +\end_layout + +\end_inset + + can be identified to form a low pass section +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[Ch.~4B, p.~4]{Hutchins1975} +\end_layout + +\end_inset + +. + +\end_layout + +\begin_layout Standard +To be able to change the cutoff frequency via voltage control the frequency + defining resistor could be replaced with a voltage controlled resistor + +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~198]{Lancaster1975} +\end_layout + +\end_inset + +. +\end_layout + +\begin_layout Subsection +Amplifier +\end_layout + +\begin_layout Subsection +Envelope Generator +\end_layout + +\begin_layout Chapter +Building a Modular Synthesizer +\end_layout + +\begin_layout Section +Introduction +\begin_inset CommandInset label +LatexCommand label +name "sec:building-introduction" + +\end_inset + + +\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 elements (see chapter +\begin_inset CommandInset ref +LatexCommand ref +reference "sub:electronic-oscillator" + +\end_inset + + and +\begin_inset CommandInset ref +LatexCommand ref +reference "sub:electronic-filter" + +\end_inset + +). + 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 +\begin_inset Note Note +status collapsed + +\begin_layout Plain Layout +For tuned modules it is important to consider whether they use a volt per + octave or volt per hertz characteristic. +\end_layout + +\begin_layout Plain Layout +Audio Signals ±5Volts +\end_layout + +\begin_layout Plain Layout +Buffering 1:10 impedance ratio +\end_layout + +\end_inset + + +\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 +\begin_inset Note Note +status collapsed + +\begin_layout Plain Layout +Oscilloscope, Multimeter, Tracking faults, measuring +\end_layout + +\end_inset + + +\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 Robert + Sontheimers audio circuit technology book +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~74]{Sontheimer2004} +\end_layout + +\end_inset + +. + 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 0in +width "22text%" +status collapsed + +\begin_layout Plain Layout +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +vspace*{-2.5em} +\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 (see chapter + +\begin_inset CommandInset ref +LatexCommand ref +reference "sub:electronic-filter" + +\end_inset + +). + 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 + utilized as an oscillator. + Therefore a volt 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 Section* +Summary +\end_layout + +\begin_layout Standard +This paper constitutes an attempt to summarize what appeared to be the most + important facts and information on the topics of history, theory and electronic +s during the research on analog synthesis. + Of course for all of the discussed could only scratch the surface. + Even only the topic of active filters circuits can (and does) fill entire + books. +\end_layout + +\begin_layout Standard +Accompanying this research a small synthesizer prototype has been set up, + making use of the knowledge aquired during the research. +\end_layout + +\begin_layout Section* +Results +\end_layout + +\begin_layout Standard +\begin_inset Note Note +status open + +\begin_layout Plain Layout +As mentioned in chapter +\begin_inset CommandInset ref +LatexCommand ref +reference "sec:building-introduction" + +\end_inset + + the process of building the prototype had not transpired as initially planned. + +\end_layout + +\begin_layout Plain Layout +cunstruction results - goals attained. +\end_layout + +\begin_layout Plain Layout +what could be done better? +\end_layout + +\begin_layout Plain Layout +what could be added, what are the next steps? +\end_layout + +\begin_layout Plain Layout +problems of with output knob. + maybe powersupply. +\end_layout + +\begin_layout Plain Layout +describe the journey, discribe the difference and natururality of analog + sound as opposed to the digital, which i only knew before. +\end_layout + +\end_inset + + +\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 Section* +Thanks +\end_layout + +\begin_layout Standard +Thanks to Eddi, Derek, Befaco, Richard, David +\end_layout + +\begin_layout Standard +\begin_inset FloatList figure + +\end_inset + + +\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 e049924..e14f752 100644 --- a/facharbeit.lyx +++ b/facharbeit.lyx @@ -364,11 +364,27 @@ Preface \end_layout \begin_layout Section* -Motivation +Introduction \end_layout \begin_layout Standard -The project was inspired by the film +This paper constitutes an attempt to summarize the most important facts + and information on the topic of analog, modular synthesizers. + The range of discussed subjects involves a series of various perspectives, + including historical, theoretical, electronic and practical viewpoints. + +\end_layout + +\begin_layout Standard +Its goal is to convey an understanding of the inner workings of electronic + synthesizers and their components. + Moreover 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. + The project was inspired by the film \emph on moog \emph default @@ -387,13 +403,7 @@ cite{Fjellestad:movie} , 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* @@ -444,41 +454,6 @@ To make it playable with a keyboard, a MIDI input module is added. \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 @@ -1200,7 +1175,7 @@ lines 0 placement O overhang 0in width "5cm" -status collapsed +status open \begin_layout Plain Layout \begin_inset ERT @@ -2099,6 +2074,10 @@ name "sub:electronic-filter" \end_layout +\begin_layout Subsubsection +Passive Filter +\end_layout + \begin_layout Standard Filter circuits are generally based upon the fact that the transfer of alternati ng currents through a capacitor becomes increasingly weak below a certain @@ -2107,7 +2086,226 @@ ng currents through a capacitor becomes increasingly weak below a certain If the capacitor is connected to the ground the high frequencies are short circuited and low frequencies remain in the signal path. This is referred to as a resistor-capacitor (RC) element. + This simple circuit represents a passive, first-order butterworth filter + with a roll-off of 6 dB per octave. +\begin_inset Note Note +status collapsed + +\begin_layout Plain Layout + The moog filter for example concatenates four of these RC elements in a + row and regulates the resistor values +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~57]{Anwander2011} +\end_layout + +\end_inset + +. + +\end_layout + +\end_inset + + To increase the slope of the filter multiple RC elements can be connected + in series +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~57]{Anwander2011} +\end_layout + +\end_inset + +. + +\end_layout + +\begin_layout Standard +Nevertheless this poses some disadvantages, because the filter stages influence + each other. + The resistor of the first filter affects the resistance of the second. + This can be dealt with by designing the second filter to have a much higher + impedance. + Unfortunately a high impedance circuit is much more prone to interferences + and signal noise +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~97]{Sontheimer2004} +\end_layout + +\end_inset + +. +\end_layout + +\begin_layout Subsubsection +Active Filter +\end_layout + +\begin_layout Standard +\begin_inset Wrap figure +lines 0 +placement O +overhang 0in +width "5.5cm" +status collapsed + +\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/Sallen-Key-Filter-Lowpass.png + display false + width 5.5cm + +\end_inset + + +\end_layout + +\begin_layout Plain Layout +\begin_inset Caption + +\begin_layout Plain Layout +Active Sallen-Key low pass filter circuit scheme +\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 + + A better and more flexible solution is the usage of an active filter design, + like the Sallen-Key filter. + This is a common second-order filter, which is applicable as a low or high + pass, whereby only resistors and capacitors have to be swapped +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~97]{Sontheimer2004} +\end_layout + +\end_inset + +. + Resistor +\begin_inset script superscript + +\begin_layout Plain Layout +2 +\end_layout + +\end_inset + + and capacitor +\begin_inset script superscript + +\begin_layout Plain Layout +2 +\end_layout + +\end_inset + + can be identified to form a low pass section +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[Ch.~4B, p.~4]{Hutchins1975} +\end_layout + +\end_inset + +. + +\end_layout + +\begin_layout Standard +To be able to change the cutoff frequency via voltage control the frequency + defining resistor could be replaced with a voltage controlled resistor + +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~198]{Lancaster1975} +\end_layout + +\end_inset + +. \end_layout \begin_layout Subsection @@ -2123,7 +2321,14 @@ Building a Modular Synthesizer \end_layout \begin_layout Section -Introduction +Introduction +\begin_inset CommandInset label +LatexCommand label +name "sec:building-introduction" + +\end_inset + + \end_layout \begin_layout Standard @@ -2148,7 +2353,6 @@ reference "sub:electronic-filter" 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 @@ -2304,9 +2508,22 @@ 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. +For the power unit a universal power supply circuit was chosen from Robert + Sontheimers audio circuit technology book +\begin_inset ERT +status open + +\begin_layout Plain Layout + + +\backslash +cite[p.~74]{Sontheimer2004} +\end_layout + +\end_inset + +. + 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. @@ -2463,7 +2680,15 @@ BF-22 Filter \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. + and is based upon the principle of the Sallen and Key filter (see chapter + +\begin_inset CommandInset ref +LatexCommand ref +reference "sub:electronic-filter" + +\end_inset + +). 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 @@ -2479,7 +2704,7 @@ This module is an extended copy of the filter from the legendary Korg MS-20 \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. + utilized as an oscillator. Therefore a volt 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. @@ -2517,23 +2742,116 @@ Output Conclusion \end_layout +\begin_layout Section* +Summary +\end_layout + \begin_layout Standard +This paper constitutes an attempt to summarize what appeared to be the most + important facts and information on the topics of history, theory and electronic +s during the research on analog synthesis. + Of course for all of the discussed could only scratch the surface. + Even only the topic of active filters circuits can (and does) fill entire + books. +\end_layout + +\begin_layout Standard +Accompanying this research a small synthesizer prototype has been set up, + making use of the knowledge aquired during the research. +\end_layout + +\begin_layout Section* +Results +\end_layout + +\begin_layout Standard +\begin_inset Note Note +status open + +\begin_layout Plain Layout +As mentioned in chapter +\begin_inset CommandInset ref +LatexCommand ref +reference "sec:building-introduction" + +\end_inset + + the process of building the prototype had not transpired as initially planned. + +\end_layout + +\begin_layout Plain Layout +cunstruction results - goals attained. +\end_layout + +\begin_layout Plain Layout +what could be done better? +\end_layout + +\begin_layout Plain Layout +what could be added, what are the next steps? +\end_layout + +\begin_layout Plain Layout +problems of with output knob. + maybe powersupply. +\end_layout + +\begin_layout Plain Layout describe the journey, discribe the difference and natururality of analog sound as opposed to the digital, which i only knew before. \end_layout +\end_inset + + +\end_layout + +\begin_layout Section* +A Personal Journey +\end_layout + \begin_layout Standard -tweaking knobs to borders where the outcome is on a threshold resulting - in unpredictable patterns. - +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 Section* +Thanks \end_layout \begin_layout Standard Thanks to Eddi, Derek, Befaco, Richard, David \end_layout -\begin_layout Section* -List of figures +\begin_layout Standard +\begin_inset FloatList figure + +\end_inset + + \end_layout \begin_layout Standard diff --git a/graphics/Sallen-Key-Filter-Lowpass.png b/graphics/Sallen-Key-Filter-Lowpass.png new file mode 100644 index 0000000000000000000000000000000000000000..e05f56cdf12e9f3e3499df2cc0d547f00364ca64 GIT binary patch literal 29820 zcmeFXRaBkJ(k=`W2yP*`y9IZL;O_436N0-04;tJhxVvkR;1V=A1b25k6V~2qtuelf z|K=a(=6v(w9j|m%S3Mvq-0`~OBuM| z0Sy;7H=Y?J5eakDz6FqM?RcHq&l5_)4_D9+-XiwNI2ZBg$hPan-J4K6d4P?gHTU2p z@2OLO5eo9>Jp|Z1Y1R|K=!q1?3mr_Q(3h1B32Y>a|66ad 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-66,6 +66,15 @@ ADDRESS = {Ithaca, NY}, } +@BOOK{Lancaster1975, + AUTHOR = {Lancaster, Don}, + YEAR = {1975}, + TITLE = {Active-filter cookbook}, + EDITION = {1.}, + PUBLISHER = {H. W. Sams}, + ADDRESS = {Indianapolis}, +} + @article{Bode1984, title={History of electronic sound modification}, author={Bode, Harald}, @@ -113,7 +122,8 @@ author={Hans Fjellestad}, year={2004}, howpublished = "[DVD]", - publisher={Plexifilm} + publisher={Plexifilm}, + address={Asheville, North Carolina, USA} } article{Vinoski:2007:RE:1304062.1304553,