Reverb Karaoke Machine

Mixed-Signal Design
Analog Signal Conditioning
Op-Amps & Active Filters
ADC
DAC
Reverb Karaoke Machine

Circuitry inside custom-printed microphone casing.

Built a mixed-signal audio processing system from scratch, handling everything from microphone input conditioning to speaker output. Analog Front-End: Designed the input signal chain starting with a low-noise op-amp pre-amp stage to bias and amplify weak electret microphone signals into a single-supply MCU-readable range. Added bandpass filter stage to reject background hum and high-frequency noise while satisfying Nyquist criteria before sampling. Custom Converters: Instead of using the MCU's built-in ADC/DAC, I built discrete converters to evaluate their performance. Implemented a 10-bit R-2R resistor ladder DAC and tested a SAR ADC topology. Added output reconstruction filtering after the DAC to smooth quantization steps and eliminate high-frequency images. Bring-Up & Debugging: Used an oscilloscope to debug clipping, ground bounce, and other sources of noise across all stages.
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Block diagram of system

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Multi-stage filter schematic

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Breadboard bring-up and converter hardware testing.

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Oscilloscope capture: Raw mic input vs. amplified & filtered output.

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Close-up of the Arduino DAC output.