Abstract
The paper describes the construction and design of an electronic analog sound synthesizer that generates audio signals. It is also called electronic musical instrument. The idea behind to make analog synthesizer is to produce and record electronic sounds and then manipulate them by using DAW (Digital Audio Workstation) like Apple company’s “Logic Pro X” software. An analogue synthesizer creates sound by using electronic circuit elements: resistors, capacitors, transistors and integrated circuits. If we observe the output of an analog synthesizer with an oscilloscope, then we see that the waveform voltage is continuous. There are few basic components that work together to forge a sound, the waveform is generated by an oscillator which changes its pitch and to change the timbre certain frequencies are being carved out by the filter.
1. INTRODUCTION AND DESIGN CONSIDERATIONS
There are voltage-controlled building blocks in the synthesizer. Following are the four parameters in the synthesizer which generate sound through various analogue techniques. First, there is Voltage- Controlled Oscillators (VCOs) in which varying voltage is used to control the frequency of a sound-producing oscillator and then Voltage-Controlled Filters (VCFs) where voltage controls the cut-off frequency of a filter circuit. At last, Low-Frequency Oscillators (LFOs) in which varying voltage is used to control the frequency of a low-frequency modulation-producing oscillator and then Voltage-Controlled Amplifiers (VCAs) where voltage controls the output amplitude of a signal.
In synthesizers, the oscillator is the initial source of the sound in which voltage from a power source oscillates electrons which generates the waveform. There are most of the synthesizers which let you select from various types of waves because different patterns have different sounds and the most common types are Sine wave (the purest form of wave), Sawtooth wave, Square wave and Triangle wave.
In today’s modern music scene these analogue synthesizers are widely used for producing music in different genres like pop, hip-hop, rock, metal and electronic dance music. Analogue synthesizers has switches, buttons, knobs, and LEDs in which each one performs a particular function and has clearly marked inputs, outputs and controls.
2. BASIC DESIGN
The analogue synthesizer project is divided into three components: the power supply, signal processing, and power amplifier stage, with focusing on the signal processing, designing, building the power supply, and power amplifier. These three systems are designed separately  and then integrated together.
Figure 1: The Overall Block Diagram for the whole system. Key presses on a keyboard
are passed to the signal processing unit that creates a tone. The tone is then driven through a speaker by the amplifier. The power supply provides power to both systems. Analog Synthesizer Module In order to create different sounds, an analog synthesizer consists of several modules that can be wired together in different ways. The wiring setup is called a “patch”. There are two different types of signals where modules connect to each other. The waveform signal is one of a type where a waveform being generated, modified or played through a speaker. The control signal is other type of signal, which determines how a module works.
The control signals have a range from zero to 5 volts and waveform signals have a voltage range of plus and minus 5 volts. Through standard output and input buffers, the signals are carried between modules via quarter inch mono cables. The synthesizer is modular in which a fixed block diagram of the system does not accurately describe how the system works but a standard patch is shown below to help understand thefunction of each module and how they can be used together.
3. HARDWARE IMPLEMENTATION
In this modular analog synthesizer, the blocks represent modules and the lines represent signals. The coloured lines represent different control signals while the black lines are waveform signals. The controller produces the control signals after reading the keyboard presses. There are five basic modules to construct standard analog synthesizer named as the controller, the voltage controlled oscillator, the voltage controlled filter, the voltage controlled amplifier, and the envelope generator. The synthesizer has the controller which is a user interface.
A VCO (voltage controlled oscillator) produces several waveforms dependent on the input signals and its knob settings. The output signals include sine, triangle, sawtooth, and square waveforms. The frequency of oscillation can either be controlled by a 1 volt per octave signal or by a potentiometer. Sometimes VCO’s have an optional input that can perform frequency modulation of the input signal and the generated signal. The frequency of oscillation can either be controlled by a potentiometer or by a 1 volt per octave signal from a controller. VCO’s sometimes have an optional input that can perform
frequency modulation of the input signal and the generated signal.
A VCF (voltage controlled filter) is controlled by potentiometer settings and input voltages. There are many types of VCFs with different output types where the system will have low pass, band pass, band stop, high pass, and notch filter outputs. The basic VCF filters an input  signal at a frequency set by input voltages and control knobs.
The VCA (voltage controlled amplifier) modify the amplitude of an input signal. VCA’s are used in combination with envelope generators. To control the amplitude of the output signal the negative control voltage will ensure the signal is turned off. Finally, the envelope generator is a module that takes in a gate and trigger the signal then generates a time dependent output signal to be used by a VCA (voltage controlled amplifier) to give the output signal a more realistic sound. The envelope generator creates an ADSR signal. ADSR stands for the four sections of the envelope, attack, decay, sustain, and release.
ADSR Envelope
4. CONCLUSION AND FUTURE WORK
In conclusion, this project involves challenges in designing the synthesizer and then integration. The modular analog synthesizer is an exciting project that will cover a wide range of Electronic concepts. There will be a power amplifier which amplify signals from the analog synthesizer at high volume. It’s also exciting and interesting to experiment with the sounds after building the analog synthesizer and then recording and manipulating them using DAWs (Digital Audio Workstations) like Apple company’s software “Logic Pro X”. I would like to illustrate all these techniques in a patchable environment. Overall, we will able to achieve output sound from the analog synthesizer and draw current from the power supply.
5. REFERENCES
[1] Thttp://electronotes.netfirms.com/
[2] http://www.electronics.dit.ie/staff/ptobin/3chapt08.pdf
[3] Self, Douglas. Audio Power Amplifier Design Handbook, 1996.
[4] Rashid, Muhammad H. Rashid. Power Electronics Handbook. Third Edition. Elseviee.
Burlington, MA: 2011.
[5] Make- Analog Synthesizers by Ray Wilso

Article Writer
Name:- Himanshu Mehta
Course:-AAFT University of Media & Arts