Marshall Berg | Math: Motion, Force, Light | 4.19.11

MINI-MOOG, A FAR OUT PRODUCT OF ELECTOMAGNITISM: AN

INSTRUMENT FOR INVENTING SOUND

The Mini Moog was first introduced to the world in 1970. A press release style ad

for the product explains its functions, “Here it is! A compact, moderately priced

electronic music synthesizer… The Mini Moog is not merely another sound modifier

built to enhance the sound of other instruments, although it can perform this function and

many more… Sound generators include three oscillators, producing pitched tines over the

entire range of human hearing with several different waveforms, a noise source for

producing pitchless sound, and a microphone/accessory amplifier through which sounds

from other sources may be introduced in to the Mini.”1 By breaking down the ideas

behind sound waves, and dissecting specific components of the Mini Moog, such as

oscillators, envelopes, and filters, I hope to explain the magnificence of this machine and

how it came to be. This instrument can only be truly understood through a discussion of

the physics behind the panel, revealing the historic breakthroughs involving

electromagnetism and circuits.

The Mini Moog operates on physical principals introduced by the theory of

classical electromagnetism. Scottish physicist James Clerk Maxwell, gathered numerous

findings from the early 19th century, concerning the curious nature of what were

previously thought to be disperate forces (electricity and magnetism) and unified the

equations into one electromagnetic theory. He published his formulas and findings

between the years of 1861-62, which are now known as Maxwell’s equations.2

Maxwell’s equations explain that electric and magnetic particles are a part of an

oscillating symbiotic relationship. These oscillations take the form of electromagnetic

waves, which travel outward from an original electromagnetic field. Electromagnetic

waves are the reaction of charged particles that emit oppositely attractive fields.3 The

electric field is in a vertical plane, the magnetic field in a horizontal plane. The interaction of

the two fields cause the wave to move as a vector through space, at the speed of light (in a

vacuum) as proven by Hertz in 1883.6 Maxwell posed that light itself is an electromagnetic

wave.

“EM radiation carries energy and momentum, which may be imparted when it

interacts with matter.”7 The energy and interaction depends on the frequency of the wave,

and the material it interacts with. All EM radiation, including light, exists as both a

particle and a wave as proven by Young’s double slit experiment.8

Once the potential of these separate forces were realized as one, inventors and

physicists alike expanded use of electromagnetic force exponentially. “When any wire (or

other conducting object such as an antenna) conducts alternating current, electromagnetic

radiation is propagated at the same frequency as the electric current.”9 The scientific search

for inventions that would control, change, and use the energy of this new found force

rapidly accelerated, lighting up the nights and minds of humanity. Edison the well known

physicist/businessman pioneered the field in the 1860’s inventing or contributing to the

production of: lights, power stations, telegraphs, motors, pumps and railways, all

powered by the energy of electromagnetism.

This first round of electronic technology operated on direct current. Direct current

is the product of the earliest electric energy storage system, the Galvanic Battery. The

first battery took the form of an array of interconnecting electrodes (metals, such as zinc

and copper) interacting in an electrolyte solution and connected with a salt bridge.10

When a particle is charged with electricity it becomes an ion11, the galvanic battery

provides a path for these ions to constantly move in one direction. In this system, the gain

of electrons is termed reduction, and the loss of electrons; oxidation. When an electrode

(zinc) is placed in an electrolyte solution it loses electrons due to a chemical reaction, this

is shown by;

Zn = Zn2+ + 2 e-

Where Zn is Zinc, and e is nature constant. This formula describes a proportional

chemical reaction of particle reduction and oxidation. This half cell is represented as;

Zn | Zn2+

Copper, in its own solution forms a similar half cell:

Cu | Cu2+

The galvanic battery operates on the combination of equal number of half-cells, these

separate elements are connected by conductor and a salt bridge. Zinc loses ions faster

than copper in its own solution, so when connected to form a galvanic cell, additional

ions are forced through the copper, regulating the direction of the current in a controlled

and calculated way; 12

Zn | Zn2+ || Cu2+ | Cu

|| describes a salt bridge

This continuous one directional flow of electricity powered Edison’s first power

station. Nicola Tesla argued that direct current was not the ideal electrical current for

large scale, long distance transmission and use of electricity. DC could only supply a

constant, continuous flow of power, regulating all devices equally along a circuit. This

required all additional circuits or devices attached to the power source to function in

conjunction with the one directional flux of current. Another major problem with this

system is the simple fact that an electric current moving through a wire loses power due

to friction of the medium, as shown by Ohm’s Law:

E=IR

Where E is voltage loss (in volts), I is the current flowing through the wire (in amps), and

R is the resistance of the wire (in ohms). The resistance of the wire includes, gauge,

length, and number of wires in a circuit.13 Power in the DC circuit could not travel far

from its source, due to its continuous stable voltage flow.

Tesla proposed the idea of alternating current to the American Institute of

Electrical Engineers in a lecture called, “A New System of Alternating Current Motors

and Transformers” in 1888. The lecture speaks to the future of electronic manipulation,

in the form of an alternating current that changes direction and voltage in the conductive

elements of the circuit depending on the components it passes through. Alternating

current was the product of the electromagnetic induction discovered in 1831, and early

“induction coils” experimented with the relationship of charging electric and magnetic

fields, and how they transform energy. In 1884 the first “closed transformers” were

created, providing an effective way to “step up/down” the voltage of a circuit.

Transformers consist of two coils of wire, wrapped around a highly magnetic metal core.

Power flows through the each wire coil and charges the core with a magnetic field, which

then translates the current, stated by:

Vs/Vp = Ns/Np

Where N is the number of Turns, V is voltage, p is the primary coil, and s is the

secondary. In this equation, energy is scaled proportionally in a circuit, allowing for

power regulation. This new technology based off the original electromagnetic

discoveries, formed the foundation for the electrical grid, and advanced circuitry. Power

could now be “stepped up and down” at transformers all over a large-scale circuits.

Allowing for transmission of power for great distances at extremely high voltages, which

could then be regulated outside of households, for safe use inside. This fueled a surge of

current regulating technology within circuits.

“One reason, perhaps, why this brand of science is being so rapidly developed is to be found in the interest which is attached to its experimental study. We wind a simple ring of iron with coils; we establish the connections to the generator, and with wonder and delight we note the effects of strange forces which we bring into play, which allow us to transform, to transmit and direct energy at will. We arrange the circuits properly, and we see the mass of iron and wires behave as though it were endowed with life, spinning a heavy armature, through invisible connections, with great speed and power with the energy possibly conveyed from a great distance. We observe how the energy of an alternating current traversing the wire manifests itself—not so much in the wire as in the surrounding space—in the most surprising manner, taking the forms of heat, light, mechanical energy, and, most surprising of all, even chemical affinity. All these observations fascinate us, and fill us with an intense desire to know more about the nature of these phenomena. Each day we go to our work in the hope of discovering—in the hope that some one, no matter who, may find a solution of one of the pending great problems,—and each succeeding day we return to our task with renewed ardor; and even if we are unsuccessful, our work has not been in vain, for in these strivings, in these efforts, we have hours of untold pleasure, and we have directed our energies to the benefit of mankind.”’

-Nicola Tesla A New System of Alternating Current Motors and Transformers

By 1970 electronic devices operating on advanced circuit technology were

emerging constantly. Circuitry had been defined with the early experiments, starting with

vacuum tubes, effectively tested the capabilities of how humans could manipulate

electricity through circuits. Circuit theory had classifiable elements, which physically

contribute to the control of a current in a circuit board. The variables in circuit theory are

I, V, Q, Φ

Where I is current, V is voltage, Q is charge, and Φ is magnetic flux. Nine elements make

up every interaction in circuit theory, in two categories; passive and active. Passive

elements include:

Resistors, which have a pre-designated resistance to a current shown by:

dV=RdI

R is a resistant constant measured in ohms

Capacitors, which store electric charge, related to voltage shown by:

dQ = CdV

C is capacitance constant measured in farads

Inductors, which produce magnetic flux as shown by:

dΦ = LdI

L is inductance measured in henries14

Semiconductors were discovered in the 1940’s and brought with it the end of

vacuum tubes and a safer more reliable set of tools for electricians to enjoy.

Semiconductors are a metallic crystal, first discovered by Russle Ohl, who hypothesized

that if Germanium crystals were pure enough, flowing electrons could be manipulated.

He was testing a crystal with only one crack through the center; he noticed that current

flowed differently through the material, depending on light sources around it. He

beckoned his colleges and they all watched as electrons passed through one side of the

crystal, but not the other. Ohl had come across a solid-state diode.15 With it came another

surge of electronic technology. Electronic components could be made smaller and

cheaper, causing the efficiency of electronic circuits exponentially increased.

Diodes, which are electronic “valves,” allow electricity to pass in one direction

through a circuit in relation to the equation below.

I = the net current flowing through the diode; ���I0 = "dark saturation current", the diode

leakage current density in the absence of light; ���V = applied voltage across the terminals of

the diode; ���q = absolute value of electron charge; ���k = Boltzmann's constant; n = ideality

factor, a number between 1 and 2 which typically increases as the current decreases, and

���T = absolute temperature (K), 16

Fully functional transistors, replaced triode vacuum tubes in 1954. Gordon Teel

abandoned the previously used Germanium crystals, for more pure silicon. Building on

previous “sandwich” models of alternating layers of oppositely charged material, Teel

was able to create a transistor element that efficiently amplified the current passing

through it.17 Finally we arrive at the most advanced component soldered on the Mini

Moog board: The Integrated Chip. An IC is a fully functional, miniaturized circuit,

integrated into larger circuits. Jack Kilby, and Robert Noyce working independently,

created IC chips around the same time at the turn of the 50’s. They formed a circuit board

and all the components on a single block of semi-conductor material, then overlaid a

connecting metal diagram.18 Robert Moog now had all the parts necessary to build a

highly advanced amplified electronic signal synthesizer.

Mini Moog

The Mini Moog is an electronic device that produces, modulates, and amplifies

electronic sound vibrations, and waves. “Technically, sound is the conversion of physical

energy—such as a hand clap—to an air pressure disturbance. This change in air pressure

is transmitted as a series of vibrations—a sound wave—through the air”19 The Mini

Moog achieves its initial “voice” from up to three oscillators.

An oscillator produces a wave by transferring energy from one form to another.

The oscillators in the Mini Moog work by charging and releasing different components in

a circuit, the energy “oscillates” (moves back and forth) from magnetic field, to electrical

charge creating a wave. Without constant charge this phenomena decreases exponentially

as shown by ohm’s law. The Mini Moog’s oscillators have a variety of controls that

allow for the change of waveform, and range of frequencies (tones) available for use on

the keyboard. These are voltage-controlled oscillators. The Mini Moog has three VCOs

connected on a single board, known as an oscillator bank. This advanced board has over

20 parameter functions, which allow the finest control over the flow of current between

components, allowing for change of frequency, pitch, and tone of each oscillating wave.

Layering oscillations provide more rich tones. When control dials are moved, differing

amounts of voltage are added, as translated through a controller chip.20 The third

oscillator can be switched into a Low Frequency Oscillator, to add inaudible frequency,

that “phases” or “flanges” sound.21

Sound then moves from each oscillator, and combines through the mixer, which

sends the three currents through separate IC’s (the mixer) that feed into one line out to the

Voltage Control Filter chip.

As the current flows into the VCF in the Mini Moog it cuts off at a frequency

determined by

22

Rcv= Resistance Cb= Capacitance Fo= Cutoff frequency. The 4 constant is determined by

the number of “poles” the filter has. A pole is simply a resistance/capacitor pairing, the

more poles in a filter, the greater the distance of attenuation. The effect of the filter is

shown below.

23

Lastly, the sound is pushed through two Voltage Control Amplifiers, which can provide

many functions to the final sound-wave output. The VCAs amplify the current, and create

a voltage generated “envelope” which is the shape of the sound as a line over time. As

previously stated the Mini Moog had two separate VCAs; one within the filter circuit and

another as a final controller for voltage controlled volume and final overall envelope

adjustment.

.

Additional modifications are available, through electronically sculpting the shape

of the envelope in different sections. The Mini Moog allows for three different parts of

the envelope to be amplified these are termed, Attack, Decay, and Release and are

directly related to the physical action of striking a key on the keyboard. They relate to the

volume (gain) of a note as it interacts with time.24

25

Robert Moog introduced the Mini Moog just ten years after the invention of the

integrated circuit. This exquisite piece of electronic circuitry, created sounds unheard by

the human ear. Musicians could now invent and modify sound to fit their specific needs.

These noises were mind-blowing, the sound of electric current moving through circuitry.

Mini Moog’s hold their value ($2000-700026), and are still in very high demand. Robert

Moog died in 2005, but last year for the 40th anniversary of the Mini Moog, the still

standing Moog corporation released the Voyager XL, by simply combining Roberts, Mini

Moog and Voyager synthesizers. No one dares to try manufacturing sound any better than

the original Moog.27,28

Moog Voyager XL NOTES:

1. “Introducing the Mini Moog model d” Moog Archives Website http://moogarchives.com/miniad.htm

2. Brewster, Hillary “Classic Electromagnetism” Electromagnetism (Oxford Book Co, Jiapar, India, 2010 ed) pg 230

3. Brewster, Hillary “Classic Electromagnetism” Electromagnetism (Oxford Book Co, Jiapar, India,

2010 ed) pg 230

4. NA

5. NA 6. “Heinrich Hertz Wireless Experiment”

(http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture6/hertz/Hertz_exp.html) “In 1887 Hertz designed a brilliant set of experiments tested Maxwell's hypothesis. He used an oscillator made of polished brass knobs, each connected to an induction coil and separated by a tiny gap over which sparks could leap. Hertz reasoned that, if Maxwell's predictions were correct, electromagnetic waves would be transmitted during each series of sparks. To confirm this, Hertz made a simple receiver of looped wire. At the ends of the loop were small knobs separated by a tiny gap. The receiver was placed several yards from the oscillator. According to theory, if electromagnetic waves were spreading from the oscillator sparks, they would induce a current in the loop that would send sparks across the gap. This occurred when Hertz turned on the oscillator, producing the first transmission and reception of electromagnetic waves. Hertz also noted that electrical conductors reflect the waves and that they can be focused by concave reflectors. He found that nonconductors allow most of the waves to pass through. Another of his discoveries was the photoelectric effect.”

7. Brewster, Hillary “Classic Electromagnetism” Electromagnetism (Oxford Book Co, Jiapar, India,

2010 ed) pg 231 8. Williams, Allen “Section 2: Young's double-slit experiment” Consciousness, Physics, and the

Holographic Paradigm (http://hermital.org/book/holoprt7-2.htm) “The modern version of Young's double-slit experiment is so refined that a recording device or photographic film placed behind the slits in line with a controlled source (emitter) can record the activity of a single photon (or electron) at a time. The single photon (or electron) double-slit experiment produces the expected particle-like results when only one slit is open; i.e., when slit A is closed and every photon (or electron) must pass through slit B, or vice versa. But with both slits A and B open the device or film records a totally unexpected wave diffraction pattern with bright and dark interference bands (A ± B) – a well-known characteristic of electromagnetic radiation (waves) – rather than the expected sum of the two trials (A + B) through alternate open slits (A or B) which produce particle-like results. This extraordinary wave-like result when both slits are open at the same time has remained unexplained since Young first performed the double-slit experiment in 1820. Indeed, the phenomenon has been called the central mystery of quantum theory by Richard Feynman” 9. Brewster, Hillary “Classic Electromagnetism” Electromagnetism (Oxford Book Co, Jiapar, India,

2010 ed) pg 233 10. “Chemistry of Batteries” http://www.science.uwaterloo.ca/~cchieh/cact/c123/battery.html 11. “Ions” Wisconsin Technical College System Online http://www.wisc-

online.com/Objects/ViewObject.aspx?ID=gch3604 12. “Chemistry of Batteries” http://www.science.uwaterloo.ca/~cchieh/cact/c123/battery.html

13. “Voltage Loss Formulas” Paige Irrigation and Lighting Division Online http://www.paigewire.com/volt_loss_formulas.htm

14. Giancoli “Chapter 21” Physics: Principles with Applications, 6th edition (UC Berkley Press, 2004)

15. “Russle Ohl Accendently Discovers the Silicon P-N Junction” PBS Online TRANSISTORIZED! http://www.pbs.org/transistor/science/events/pnjunc.html

16. “Non-Ideal Diodes” http://pvcdrom.pveducation.org/SEMICON/EQUAN.HTM a. “Diode” The Electronics Club http://www.kpsec.freeuk.com/components/diode.htm

17. “The First Silicone Transistor” PBS Online TRANSISTORIZED! http://www.pbs.org/transistor/science/events/silicont1.html

a. Transistors serve a variety of functions. Transistors can be used as a switch, NOT gate, or amplifier and serve all these purposes in the mini moog. For more information on functions and equations of transistors please see: Riley, Lewis “Transistor Circuits” Ursinus College Online http://webpages.ursinus.edu/lriley/ref/circuits/node4.html (2001-2004)

18. “The History of the Integrated Circuit” Nobel Prize Online

http://nobelprize.org/educational/physics/integrated_circuit/history/ 19. How Subtractive Synthesizers Work” Apple Logic Help Guide: Synthesizer

Basicshttp://documentation.apple.com/en/logicexpress/instruments/index.html#chapter=A%26section=3%26tasks=true

20. Note the user defined parameters and control functions as black boxes

21. For more information see: http://www.geofex.com/article_folders/phasers/phase.html 22. “Low Noise V.C Signal Processor Manual” Curtis Electromusic Specialties (Jan 1987) 23. Russ, Martin “Subtractive Synthesis” Sound Synthesis and Sampling (Linacre House, Jordan Hill,

Oxford, 1997) pg 115 24. For more information on envelopes see: “Circuit Envelope Simulation” Aglient Technologies

which describes the ADR envelope at length, http://www.ece.uci.edu/eceware/ads_docs/pdf/cktsimenv.pdf

25. Russ, Martin “Subtractive Synthesis” Sound Synthesis and Sampling (Linacre House, Jordan Hill, Oxford, 1997) pg 120-121

26. Screen shot of Ebay search term “Mini Moog” taken 4/28/11

27. Crawford, Franklin “Robert Moog Ph.D 64, Inventor of the Music Sythesizer, Dies of Brain

Cancer” Cornell University News Science Online http://www.news.cornell.edu/stories/aug05/moog.obit.fac.html

28. “Moog Music announce Moog Voyager XL” Resident Advisor Online http://www.residentadvisor.net/news.aspx?id=12823