Audio oscillators are widely integrated in generating waveforms in a particular frequency range between 16 Hz and 20,000 Hz. For a low-frequency oscillator, waveforms below 20Hz can only be generated. Audio oscillators are designed to be used in producing music as tone generators.
Also, these oscillators allow the measurement of compression and circuit gain at a given frequency. Here, we will explore audio oscillators, its types, and applications.
What is an Audio Oscillator?
An audio oscillator serves as measurement tools and tone generators in music production. An oscillator is designed to convert direct current (DC) to alternating current (AC), which generates an alternating waveform. Furthermore, oscillators help to produce waveforms in a given frequency. A low-frequency oscillator produces waveforms that are less than 20Hz.
There is a quick alternation of the electrical current between two states. This generates a waveform you can amplify and shape with different audio processors. Electronic oscillators are applicable in several industries like measurement, calibration tools, and equipment clocking.
Audio oscillators usually generate sound. Their circuitry quickly changes between two states. This is similar to the way a vibrating string generates a sound. The oscillating electronic circuit produces a waveform which you can amplify and integrate as a sound source.
Types of Oscillators
The Voltage-controlled oscillator or VCO is the most common type of oscillator used in analog synthesizers. A control voltage determines the frequency of the VCO audio oscillator. The VCO oscillator generates a different frequency based on the control voltage you feed it. When you press a key on an analog synthesizer, a certain voltage is sent to the oscillator. This produces a waveform in the pitch.
If you tune the oscillator properly, the pitch will work in line with the key’s note. Furthermore, with synthesizers, you can regulate the control voltage using various types of signals. For example, a Frequency Modulation also known as FM synthesis can be generated by including modulation to a VCO.
VCO audio oscillator comprises three parameters which include volume, frequency, and waveform. Let’s have an in-depth analysis of how these parameters related to a sound by looking at a sine wave.
A sine wave is the most important aspects of all waveforms. You can alter the shape of waveforms by adding harmonics. Square, sawtooth, sine, and triangle are the primary waveform shapes. Each of these shapes affects the tone of the sound generated. Also, sine waves usually have a smooth sound. On the other hand, sawtooth can be buzzy.
Noise is another waveform oscillators experience. It usually comes in pink and white variety. While the frequencies of white noise are in equal proportions, pink noise reduces the effect of some of the higher frequencies.
Digital oscillators produce waveforms by integrating DSP or digital signal processing. These waveforms are digitally recreated to look like analog oscillators. There has been some development in modeling technology, however, a good number of synth enthusiasts usually consider the sound of digital oscillators to be inferior to analog.
Types of Waveforms
Oscillators generate cyclic waveforms. These waveforms are measured in Hz i.e Hertz. There will be more cycles of the oscillator vibrates faster. Oscillators are known to generate different types of shapes. However, the most common shapes on an analog synthesizer include sawtooth, sine, triangle, and square. The waveform line’s curve determines its shape.
Square wave
A square wave includes harmonics that are seen in odd-number multiples of the basic frequency. Also, a square wave looks like a square.
Sawtooth wave
The sawtooth wave looks like a sawtooth blade. Odd and even harmonics are added to a sawtooth wave. Therefore, this causes a clear tone.
Sine wave
The most basic foundation of sound is the sine wave. Sine wave is pure since it has no additional harmonics included in the signal. A sine wave comprises the fundamental frequency.
Triangle wave
A triangle wave has a similar appearance as a sine wave. However, the only difference is that a triangle wave has straight edges that link like a triangle. Odd harmonics are usually added to triangle waves.
History of Audio Oscillator
Audio oscillators were not really suitable for modern applications in the late 1930s. This was because of their cost, complexity, and instability. Therefore, William Hewlett was inspired to design and develop the model 200B variable oscillator which was the first product by the Hewlett Packard company.
After Hewlett attended a seminar at Stanford University, he was inspired to develop an efficient audio oscillator. In this seminar, Frederick E. Terman, Hewlett’s professor, discussed the integration of negative feedback. This inspired Hewlett to spend time studying this topic for his thesis.
Hewlett’s oscillator was different in that he used an incandescent lamp as the temperature-dependent resistor. Furthermore, the light bulb functioned as an automatic gain control. This kept the loop gain of the oscillator very close to unity. This is important to achieve the least amount of distortion. The output could easily be controlled without distortion due to this design.
This performance wasn’t only enhanced, but also made cheaper. At that time, the model 200A was sold at 54.40 dollars, which was less expensive than other oscillators in the market which were sold within $200 to $600.
The first method for producing audio signals was the Hewlett oscillator. Before the advent of the Hewlett’s 200B, there was no accurate way to generate low-frequency signals.
What is HP 200A Audio Oscillator?
The HP 200A audio oscillator is a low-distortion audio oscillator specially designed for carrying out test on sound equipment. This oscillator makes use of the light-bulb stabilized negative feedback circuit. Over the years, HP oscillators were integrated for the production and maintenance of radios, telephones, stereos, and other audio equipment.
The HP200A audio oscillator was developed by Bill during his postgraduate research. As at that time, Bill had an innovative and practical idea of how to use a light bulb to provide solutions to the regulation pf the circuit’s output without any interference. Although there were other oscillators, there were unstable and costly. Bill could simplify the circuit by using the light bulb. Also, he was able to enhance the performance of the oscillator and as well minimize the price.
Bill and Dave designed the HP 200A audio oscillator, their first product. The HP 200A oscillator was dubbed in such a way that it looked like it had been existing for a while. This oscillator was priced at 54.40 dollar. The oscillator was less expensive than the competitive equipment at the market as at that point in time.
According to Dave, the HP audio oscillator served as the foundation on which the HP company gained popularity and became one of the world’s largest producers of electronic instruments.
The Wien Bridge Oscillator
The Wien Bridge oscillator was designed for producing audio frequencies. This oscillator has more advantages. It is better than the phase shift oscillator since the produced frequency may be within the range of 1:10.
Wein Bridge oscillator produces a wide range of frequencies. It produces sine waves and is based on a bridge circuit created by Max Wien for measuring impedance. There are two capacitors and four resistors in this bridge. In most cases, the Wien Bridge oscillator helps to identify unknown values of components.
Most times, this oscillator is usually integrated in the audios. Also, this oscillator is mainly used for testing audio. It can generate clock signals used for testing filter circuits. Another application of this oscillator is in testing of amplifiers. Wien Bridge oscillator can help to carry out distortion testing of power amplifiers.
In this oscillator, when there are lower to higher frequencies, at a certain frequency, the capacitor reactance and the resistance are equal to each other. Therefore, there has to be a maximum output voltage.
What is the 555 Audio Oscillator?
The 555 audio oscillator is used for producing stable square wave output waveforms of various duty cycles that ranges from 50% to 100 % or a fixed frequency of about 500kHz. In order to produce a 555 audio oscillator circuit, you can link the 555 timer IC in astable mode.
This oscillator serves several purposes; therefore, it is used in many applications. You can use the 555 audio oscillators in various waveform generator circuits and applications where low output current is required. Furthermore, 555 oscillator is ideal for use in producing accurate pulse, square, and sine wave forms. It is a type of relaxation oscillator.
This oscillator can be easily built to flash a few LED’s. However, there is one simple way to develop a science project by integrating an astable 555 oscillator is Electronic Metronome. Electronic Metronome is a device that marks time in pieces of music by generating a recurring beat.
Conclusion
Oscillators are the best and easiest way to produce a particular frequency signal. The oscillation’s frequency can vary. However, audio oscillators work within a frequency range. Audio oscillators are widely integrated in several applications. You will find them in TV, radios, and other devices.
Audio oscillators usually generate sound. Their circuitry quickly changes between two states. This is similar to the way a vibrating string generates a sound.
