Grey = whole step

Beige/transparent = half step

Dyes are a colored substance that chemically bonds to a substrate. Pigments, on the other hand, do not chemically bind. Dyes are often in an aqueous solution and may need a mordant so that they effectively bind with their substrate. Some dyes are soluble in certain solvents while pigments are not soluble.  

Resist Dyeing

Resist dyeing is a technique used to create patterns with die. You can use wax, a special paste from starch or mud, or tying or stitching to make a pattern with resist dyeing. Simply cover or hide the part you don’t want to dye and then dye the remaining area. Some common types of resist dying include tie-dye, batik, and ikat.

What are Types of Dyes?

Acid Dyes

Acid dyes are water-soluble and anionic. They work well on silk, wool, nylon, and modified acrylic fibers and can be used with neural to acidic dye baths. Acid dyes attach to fibers via the salt formation of cationic and anionic groups.

Basic Dyes

Basic dyes are water-soluble and cationic. They work well on acrylic fibers as well as some wool and silk. Sometimes, acetic acid is added to the dye bath so the dye binds to the fiber. Basic dyes are commonly used to color paper.

Direct or Substantive Dyeing

Direct or substantive dying is used on cotton, wool, nylon, wool, and leather. It works with a neutral or slightly alkaline dye bath that is at or near boiling point.

A compressor is an audio tool that makes soft sounds louder and louder sounds softer. Ultimately, it can help make your final mix punchier, more colorful, and balanced.

Feed-Forward Circuit

When a signal enters a compression circuit, it is split. One copy of the signal goes to a variable-gain amplifier. The other copy of signal goes to a control circuit where the level of the signal is measured and the appropriate amount of gain is applied.

What is Threshold?

Threshold is a key control for most compression circuits. Above the threshold, the audio signal gets treated. If a signal does go above the threshold setting, two other controls go into effect – attack and release.

Attack controls how quickly the compression function is applied. Release determines how long the compression function keeps being applied after the signal has fallen below the threshold.

First off, sound is a wave. There are many types of waves – air or sound waves, waves that travel through water, waves that travel through the earth (earthquake waves or seismic waves). Waves that travel through different mediums do have some different qualities, but they also share a lot in common. Here are some common attributes of waves.

Crest: This is the maximum point of a wave

Trough: And the minimum, or lowest, point of a wave

Wavelength: The distance between two crests or two troughs

Amplitude: The distance from the center line of a wave to the trough or crest

Frequency: This is the number of waves that pass a fixed point within a second. A wave includes a crest and a trough.

Speed: This is product of the wavelength and frequency of a wave

Direction: Well, which direction – left, right, up, down – the wave is moving in

Water waves are transverse, meaning that they have an up and down motion to them, while air waves are longitudinal, meaning they have a side to side motion, similar to a spring.

Sound waves are often depicted as a sine wave. In this case, you can think of the high parts as moments when the air particles are very compressed and the low parts as moments when the air particles are farther apart. These moments can describe changes in air pressure which we ultimately detect as sound.

An equalizer is used to change the tonal quality of audio that passes through it. It does this through filter circuits and typically adjusts the gain of audio signals in specified frequency ranges. A gain increase is called a boost and a reduction in gain is called a cut.

High Pass Filter

A high pass filter, also called a low-cut filter, reduces the level of audio frequencies below a set ‘cutoff’ frequency and leaves the level above it unchanged.

Low Pass Filter

A low pass filter, also called a high-cut filter, reduces the level of frequencies above a cutoff point and leaves the level below it unchanged.

High and low pass filters are typically good for cutting gain, not boosting it. Often, the cutoff point refers to a point where there is about 3dB of gain reduction. The cutoff point does not mean that all frequencies above and below that point are untouched. Rather, there is typically a gain change around the cutoff point and the increase of gain reduction occurs smoothly. It is not a straight line.

Shelving Filters

Shelving filters apply an equal amount of gain change to all the frequencies beyond the selected shelving frequency. This differs from the progressive gain change that occurs beyond a cutoff point. The user also selects the amount of cut or boost to apply.  Similar to the cutoff point, the shelves are not ‘ideal’.

Shelving filters offer a gentle tonal adjustment for the signal. For many equalizers there are a treble tone control and bass control. The treble control is the gain control for the high shelving filter and the bass control sets the low shelving filter. Often, the mid-range does not have a shelving control and is left alone.

Peaking Filters

Peaking filters are best for targeting specific frequency bands with greater accuracy. The user selects the amount of gain to be applied and selects the center of the frequency band to be adjusted. Another control, referred to as Resonance, Bandwidth, or Q, controls the width of the band of frequencies. The narrower the bandwidth, the higher the resonance or Q.

Selecting a narrow bandwidth can be ideal when dealing with hum, noise, and vocal sibilance. A lower bandwidth is best for general tonal shaping.

A diode is an electronic component with two terminals. It typically conducts current in just one direction, known as asymmetric conductance, and has low resistance in one direction and a very very high resistance in the other.

Semiconductor diodes are the most common types of diodes today and consist of a crystalline piece of semiconductor material with a p-n junction that is connected to two terminals. The now obsolete thermionic diode is a vacuum tube. This tube has two electrodes – a heated cathode (electron emitter) and a plate or anode (electron receiver). Electrons can only from from the cathode to the plate.

What are they used for?

Diodes serve many useful purposes. Some common uses include:

• Rectifying or converting alternating current (AC) power to direct current (DC)
• Demodulating signals
• Sensing temperature
• Emitting light

Check Valve

A more intuitive way of understanding a diode is to think of it like a check valve. This is because it only allows an electric current to pass in one direction – called the diode’s forward motion – and blocks current in the opposite direction – called the reverse direction.

Reverb is a common effect used in the audio world to create a sense of space. The word “reverb” is short for reverberation. Reverb is a natural occurrence, and happens when sound waves bounce off surfaces and head out in all directions. Reverb specifically refers to early reflections of the sound waves. This is the sound that reaches us just a few milliseconds after the direct sound. It is quite similar to an echo, but echo refers to a long reflection of sound on a far away hard surface. 

Before the advent of digital reverb tools, spring reverb and plate reverb were commonly used in the music industry.

Spring Reverb

Spring reverbs consist of a set of springs inside a metal box with a transducer on one end and a pickup on the other. As sound is fed through the box, it travels across the spring and bounces the spring back and forth. A pickup converts the mechanical motion of the spring back into an electrical signal which is typically added back to the original “dry” sound. Because low-end frequencies are often more able to travel the length of the spring, they are picked up more in a spring reverb.

Plate Reverb

Plate reverb was one of the first types of artificial reverbs used in recording. It consisted of a steel plate (sheet metal) help under tension by springs. When sound waves hit the plate, it would vibrate and the vibrations would be picked up by a contact microphone

A capacitor stores electrical energy. It typically has two closely spaced metallic surfaces that are insulated from each other by a “dielectric” or non-conducting material. When a voltage is connected across the metallic surfaces, an electric field develops across the dielectric and a net positive charge collects on one surface and a net negative charge collects on the other. Thus, there is a store of electrical energy, similar to a battery.

Permittivity

There are many types of dielectric material, such as mica, glass, air, paper, mylar, and electrolytic materials. These materials have different permittivity ratings, which define how nonconductive they are.

Audio amplification applications

Capacitors couple constant DC signals with rapidly fluctuating voltages that drive speakers. This helps create a smooth sound. Further, capacitors can help limit the amount of noise between the power supply and the audio driving circuitry, resulting in a clearer sound.

The best types of capacitors for AC coupling include electrolytic and tantalum. Electrolytic offers the best performance since it is very linear when biased by Common Mode voltages. Further, their low ESR or equivalent series resistance makes them act like an ‘invisible’ component. However, they do have a large footprint and ‘dry out’ over time, especially in high temperature environments. While tantalum capacitors are more expensive, they do not dry out and have a smaller footprint.

A semiconductor is an electronic component that makes use of a semiconductor material, such as silicon, germanium, and gallium arsenide. These materials are defined by their electrical conductivity value, which falls between a conductor like copper an an insulator like glass. Further, their resistivity falls as temperature rises (unlike metal which acts in an opposite manner). The conductivity of a semiconductor can be altered through a process known as “doping”.

Doping is when impurities are added the crystal structure of the semiconductor. This alters the number of charge carriers which include electrons, ions, and electron holes. There can be many differently doped regions in a semiconductor crystal and the points where the different regions meet are called semiconductor junctions. These junctions give rise to interesting electronic behaviors and have led to the development of diodes, transistors, and other modern-day electronic devices.

Semiconductor materials typically are located near the “metalloid staircase” on the periodic table. Silicon and germanium are the most commercially important materials and they are effective because they have 4 valence electrons in their outermost shell. This means that they can gain and lose electrons equally.

Semiconductors offer many useful properties.

1. They can pass current more easily in one direction than another.
2. They have variable resistance.
3. They are sensitive to light and heat.

The conductivity of silicon is increased when small amounts of pentavalent atoms (antimony, phosphorus, arsenic) or trivalent atoms (boron, gallium, indium) are added to the crystal. Doping increases the number of charge carriers (electrons, ions, electron holes) within the crystal. When a doped semiconductor has free holes it is called “p-type” and when it contains free electrons it is called “n-type”.

To my surprise, speakers and microphones are actually very similar – just serving opposite functions. While a speaker converts an audio wave into an air wave (what we hear), a microphone converts an air wave into an audio wave.

How Does a Speaker Work?

A speaker is a transducer, meaning that it transforms energy from one form into another. In this case, it is transforming electrical waves into sound pressure waves.

There are two main components to a speaker: the driver and the cone. An amplifier sends a signal to two terminals located on the back of the driver. This current then travels through a cylindrical coil of wire that is suspended between poles of a magnet. As the signal travels through the coil, it moves back and forth with the direction of the signal.

The center of the speaker cone is attached to one end of the coil and gets driven back and forth as well. As the cone moves, it pushes and pulls the surrounding air to create pressure waves, which we interpret as sound.

How does a Microphone Work?

Like speakers, microphones are also transducers. However, microphones convert sound waves into electrical waves. When a microphone diaphragm encounters sound waves it vibrates and creates a corresponding audio signal. Three main types of microphones, the condenser,  dynamic microphone, and ribbon microphone act in similar ways.

Condensor Microphone

The condenser microphone works in a similar way to a capacitor. Inside the microphone capsule is a diaphragm, which also functions as one of the plates of a capacitor. As sound waves hit the diaphragm it moves closer to a fixed backplate. The changing distance between the two plates changes the charge-storing ability of this “capacitor” which creates a corresponding electric current to the original sound wave.

Dynamic Microphone

A dynamic microphone also has a diaphragm which moves back and forth when sound waves hit it. Similar to a speaker, a coil and magnet are attached to the diaphragm. When the diaphragm moves, the coil moves too. As the coil moves, the magnet situated inside the coil causes an electric current to move through the coil.

Ribbon Microphone

Ribbon microphones use a thin ribbon of very lightweight metal to transduce the velocity of air particles (rather than pressure) into electrical waves. The metal is held between poles of a magnet and due to Faraday’s Law, the metal ribbon creates a tiny voltage as it vibrates from changes in velocity.