Design and Experimental Verification of a Prototype Guitar Amplifier

Abstract

This project presents the design, construction, and experimental verification of a prototype guitar amplifier system, developed using standard analog audio design principles and validated through staged breadboard prototyping. The system consists of a Class- D power amplifier module and a custom analog preamplifier capable of accepting both guitar and auxiliary line-level audio inputs. Phase 1 verified the power amplifier and speaker stage using a TPA3116D2-based Class-D module. Phase 2 implemented a single-supply guitar preamplifier using a TLC272 operational amplifier with a resistive bias network, achieving a measured small-signal voltage gain of approximately 7.35 at 1 kHz with a 12 V supply—sufficient to bring guitar signal levels into the power amplifier’s usable input range. Input clipping was first observed at approximately 0.92 V peak input amplitude. Qualitative frequency sweeps indicated audible output over much of the nominal 20 Hz to 20 kHz range, though the acoustic response was not quantitatively characterised. The project also includes preliminary Phase 3 digital signal processing results: a delay and a Schroeder reverb effect were implemented on an ESP32 microcontroller with a PCM5122 Digital-to-Analog Converter (DAC) and verified using internally generated test signals. Analog-to-Digital Converter (ADC) integration could not be completed; both PCM1808 modules from the same production batch failed to produce output, likely due to a manufacturing defect. Major design choices are motivated using circuit calculations and experimental observations. A 3Dprinted enclosure was designed and manufactured. Battery integration and full DSP chain verification remain as future work.