Mark Matamoros ITP Blog

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Fall 2019

Spring 2020

Fall 2020

Homemade Hardware

Week 11: Final Project. April 23, 2020.

MINIATURE SYNTHESIZER

As I have longed to create an analog synthesizer for quite awhile, I chose to build one for my final project, where it is comprised of two triangle oscillators and a low pass filter. It is playable through the utilization of potentiometers, where they control the oscillator frequency, oscillator amplitude, filter cutoff frequency, filter resonance, and system output. Perhaps the closest representation to this build are the Eurorack 500 series synthesizer modules. Though, my intent with this project is to have it fabricated in a tabletop fashion, typical to synthesizer keyboards.

Regarding inner components, the oscillator and filter circuits will be contained within a 2" x 3.3" PCB. While the enclosure has yet to be fully realized, I will be utilizing the remainder of this semester to design it within Vectorworks. I will attempt to maintain a minial aesthetic, similar to my initial rendering. The material will solely consist of oak, pertaining to both enclosure and knobs. Additionally, labels will not be present, as I intend to promote the exploration of the instrument.

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DEMONSTRATION

PROCESS

The circuits were designed around ALFA RPAR's AS3340 and AS3320 ICs; the former is a voltage control oscillator and the latter is a voltage control filter. The utilized resistors and capacitors for the AS3340 were handled in accordance with the manufacturer's technical document. Regarding the AS3320, the design mirrored an older CEM3320 (original IC) low pass design. It must be noted that the amplifier module for the system output will not be included in the final design, as it was only utilized for demonstrative purposes. However, the potentiometer for this output will be included in the project.

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Regarding the construction of the prototype, I began with individually building each oscillator and filter within breadboards, followed with breadboards for the the filter's potentiometers and system output. As I had not built an analog synthesizer before, separating each component allowed for an efficient means of troubleshooting within the building process.

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Upon verifying the functionality of each component, the project was rebuilt with the utilization of perf boards. The primary reason for this choice pertained to the excessive noise that was generated during the breadboard process.

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It must be noted that sockets were utilized within this final prototype, as they provided a means of ensuring the safety of the ICs during the soldering process. Furthermore, these ICs can be easily removed if the ICs become a necessity for another project. Additionally, smaller sockets were cut in half and utilized for establishing connections between the circuits. While this approach provided a quick means of troubleshooting for the final prototype, they also acted as a means of modularizing the components for circuit exchanging.

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Regarding power, the utilized ICs required both negative and positive (15v) voltage for functionality; hence, two power supplies were required. An additional power supply (via Arduino) was also necessary for this work, as the control voltages and system output amplifier required a smaller voltage source (5v and 3.3v).

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It must be noted that this process granted a further appreciation in prototyping circuits for audio, as distortion and noise plagued the system within the initial breadboard build. Additionally, the safe handling of ICs within this process also became more critical throughout the work, as it appears that I damaged one oscillator IC and one filter IC. I am currently under the impression that this damage was caused through either improper cicuit connections or power handling (on/off).

PCB DESIGN

As mentioned within the introduction, the design of my PCB is rather small with its 2" x 3.3" dimensions. This design choice was made for flexibility in the creation of the enclosure and potentiometer holder. With that said, creating this small profile took a great amount of time, especially since I intially intended to design it without vias. However, under the guidance of my instructor, I forgoed this notion and utilized the other side of the board. This alteration then allowed further flexibility in the design, therebye allowing for a smaller profile.

Regarding components, capacitors, resistors, ICs, and connection points solely exist with the PCB. All other elements, such as the potentiometers and power supplies, will be connected after the PCB has been fastened within the enclosure.

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The following links contain the Eagle files for my PCB design:

Project SCH

Project BRD

SCH PDF

BRD PDF

FINAL THOUGHTS

When the ITP facilities reopen, I am intending to utilize a CNC for the enclosure and knobs. Additionally, I am highly considering the creation of a through hole design for my PCB. While SMDs can grant a smaller profile, I am curious how small I can create my PCB in this alternate manner.

It must be noted that I have not solidified the power connectors for my project. While the current setup can be functional with the input points, I would like to investigate other options for a more secure power connection.

Lastly, I am also planning to investigate spring reverb and distortion designs. As the current audio capabilities of this project are somewhat limited, it would be nice to allow the user to further alter the generated signals.



Week 10: Final Project Update. April 16, 2020.

The first draft of my Eagle schematic has been completed for my final PCB design. The following downloadable links pertain to this project:

SCH PDF

BRD PDF

Project SCH

Project BRD

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Week 8: Functional Prototype. April 2, 2020.

The following prototype was designed in accordance to Week 6's final project presentation. It must be noted that there were some slight adjustments to the power supply. I'm under the impression that the utilization of breadboards within this setup are causing powering issues, in addition to extra noise.

I'm intending to transfer the circuit components to perfboards within the near future.

Synthesizer Setup: