Mark Matamoros ITP Blog

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Fall 2019

Spring 2020

Fall 2020

Prototyping Electronic Devices

Final: Basic Synthesizer withOUT Stretch Band Control Prototype. December 7, 2020.


In accordance with my previously documented midterm, I continued my work with an analog oscillator circuit. Within this iteration, the breadboard was replaced with a perfboard, securing the sensitive connections for this particular type of circuit. Additionally, an ATmega328 became the heart of another perfboard, where this microcontroller acted as means of manipulating control voltages for the oscillator circuit.

Unfortunately, during the construction of this project, the utilization of the conductive rubber cords proved to be inadequate for my intended means of interaction. Specifically, my desired string tension caused the material to rip in half. Despite suffering this setback, this testing will prove to be a valuable piece of infromation, as this project was intended to serve as a protoype for my thesis work.



Stated in the November midterm posting, an AS3394 was utilized for sound generation. However, the means of supplying power differed within this iteration, as a reverse voltage module was implemented to handle the dual rail setup. As mentioned within the prior paragraph, an ATmega was secured within a perf board to function as a means of manipulating control voltages. It must be noted that the same amplifier module was utilized for output purposes.

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Midterm: Basic Synthesizer with Stretch Band Control Prototype. Octorber 27, 2020.


For my final project, I chose to create a synthesizer with the utilization of an AS3394 (IC), a microcontroller for CV, and a conductive rubber band for dictating the outputted CV level. This work was birthed from my desire to dive in analog synthesizers in conjunction with uncommon controller components.



While I previously utilized the AS3340 (oscillator) and AS3320 (filter) in a prior work, I chose to pick up the AS3394 IC, as it has both oscillator and filter components integrated into one unit. Furthermore, the required voltage is significantly less than the previously mentioned IC's.

Regarding the stretching rubber component (resistor), it is currently being utilized to control the frequency of the oscillator. Within this setup, the rubber band is set up in a voltage dividing manner, where the signal is being sent to an input of the microcontroller. Thereafter, the recieved values are mapped in a manner to be utilized as a control voltage through the utilization of the microcontroller's PWM capabilities.

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It must be noted that the rubber cords are being fastened to a cardboard box within this prototype.

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The following videos display two instances of modulating the oscillator frequency. The first one showcases a simple interaction between an automated sweep of the microcontroller's PWM output. The latter displays the utilization of the rubber resistor in conjunction with the microcontroller and IC.


While the current IC uses a more manageable voltage (-6.5v and 5v) for operation, the control voltages for various aspects of the IC have voltages than range in values that appear to not be typical (EX: -2v to 2v, -2 to 4v, etc.). Due to this situation, I was unable to utilize other aspects of the IC; I blame my inexperience in this type of work. In light of this situation, I am considering a swap of this IC with the previously mentioned AS3340 and AS3320, where the CV's range in the range of 0 to 5v.

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