Analog-Digital Hybrid Synthesizer

Initial Project and Group Identification

Group 28 members:

Clapp, David - Computer Engineering Herr, Matt - Electrical Engineering Morcombe, Kevin - Electrical Engineering Thatcher, Kyle - Electrical Engineering

Project Description

Synthesizer. A synthesizer, or “synth”, is an electronic musical instrument that generates electronic signals that are converted to sound through instrument amplifiers. Most commonly, a synthesizer will take the form of a piano keyboard (Figure 1). However, instead of keys that strike metal strings on a piano, the synthesizer’s keys strike electronic contacts sending a signal to the system. Synthesizers come far and few in terms of capabilities. Synths without controllers are often controlled via a MIDI device.

Figure 1 -- Two-Octave Synthesizer

MIDI. MIDI (musical instrument digital interface), is a standard for digital interface that allows many related devices to connect and communicate with one another. Such devices include computers and electronic musical instruments. MIDI carries messages that dictate pitch, velocity and control signals. A single MIDI link can carry up to 16 channels of information.

Analog Synthesizer. Since as early as 1920, analog synthesizers were developed through the use of tube amps and other electro-mechanical technologies. Into the 1960s analog synthesizers were realized through the use of op-amps and potentiometers. Integrated circuits were developed and used to control and adjust sound. Analog synth modules include voltage controlled oscillators (VCOs), low frequency oscillators (LFOs), voltage controlled filters (VCFs), voltage controlled amplifiers (VCAs), ring modulators, just to name a few. Analog synthesizers use analog electronics and samplers, which play back digital recordings of acoustic, electric or electronic instruments. An analog synth is made up of sound-generating circuitry and modulators.

Digital Synthesizer. A digital synthesizer is a synthesizer that used digital signal ​ processing (DSP) techniques to make musical sounds. A digital synthesizer is in essence a computer with a piano-keyboard and a LCD as an interface.

Analog synth vs. Digital Synth. The main difference between the two, is that digital ​ synths use digital processors while analog synths use analog circuitry. Since computer technology is advancing rapidly, it is possible to offer more features in a digital synthesizer rather than an analog synth. However, both technologies offer their own merit. Many industry experts prefer the rich, natural sound that an analog synth can provide.

Our Project. The focus of this project will be developing the components and PCBs that ​ make up an analog synthesizer. Compiling and cascading all the components into a working system will be the heart of the design. MIDI interface will allow the system components to communicate effectively. Through the use of a microcontroller, features can be added to the system to make our design unique.

Project Requirement Specifications

Hardware: The hardware of this device should be capable of generating an analog waveform signal in the VCO (voltage controlled oscillator) that can be modified by filter and modulation circuits which follow after. At the end of the chain of circuits comprised within the synthesizer will be an audio output.

Some analog components such as Human interface devices will allow a user to provide information to the microcontroller to be interpreted to the analog devices within the synthesizer.

Software: The primary objective of the software will be analyze and translate human interface devices from the synthesizer components to Musical Instrument Digital Interface (MIDI) format and export to compatible devices.

The secondary objective will be to interface and control portions of the human interface devices to allow fluid software adjustments to input waveform.

The main features of the program will be: ● To analyze input signals ● To control human interface devices ● To convert input to MIDI format ● To output MIDI to physical port

The main goals of the software will be: ● High sample rate for the input signal ● Low latency from input signal to output signal ● Low computational power usage ● Lightweight program code

The goals listed above are vital to the success of the project based on the limitations of using a microcontroller unit with minimal computational power and limited memory.

House of Quality Diagram

Table 1: Engineering-Marketing Trade-Off Matrix

Project Block Diagram

Figure 2

● Shared ● Kyle Thatcher ● David Clapp ● Kevin Morcombe ● Matt Herr

VCO (Voltage Controlled Oscillator)-The core of the synthesizer. This ​ component will generate a waveform which will Vary in frequency depending on the voltage in.

Signal Mixer: Mixes the volume of the VCO outputs prior to making way to the ​ following circuits.

Filters-The filters will be responsible for subtracting unwanted frequencies from ​ the generated tone, allowing for versatility in the synthesizer's output sounds.

Audio amplifier- Responsible for altering the output signal from the synthesizer to an audible level.

Modulator-Responsible for introducing a signal that will modulate or add motion ​ to the current signal depending on which filter or function it controls.

Human Interface- Includes devices such as potentiometers or buttons that will ​ instruct the Microcontroller to alter the state of the current function within the Synthesizer.

Microcontroller-The brain of the synthesizer, will control the various inputs to ​ the analog features and send and receive digital information with external Midi enabled devices.

Project Budget

Description Vendor Price Quantity Total Cost

Microcontroller $15 1 $15

Custom PCB $50 1-5 $50 - $250

Various Components for $100 $100 filters, oscillators, modulators

Misc unforeseen costs $100 $100

Total $265 - $465 Table 2: Preliminary Budget

Shown in the chart above is a rough estimate of the budget for the project. As more research is done on the specifics of what we will need and specific vendors/manufacturers are identified this budget will be adjusted accordingly. Parts that fail or malfunction are partially accounted for in the misc unforeseen costs, however, it’s possible that additional money will be spent on replacements. As of now, there is no sponsor and team members will split all costs evenly.

Project Timeline

Table 3: Project Timeline

Conclusion

As we are a group comprised of three electrical engineers and one computer engineer, it’s only logical that we choose a project that is heavy on the electrical design side of things. Building an analog-digital hybrid synthesizer perfectly fits this description while allowing for enough difficulty to challenge us all. There is a lot of research still to be done and there are certainly a few unforeseen obstacles in our path, however, because this project is a combination of many of the concepts we have been studying during our undergraduate career, we believe we can overcome any problems that arise. We could not be more excited to get started on this project and see what we can accomplish!!