The case itself is a treat, as it borrows design elements from another bit ... The pains he went to to get the spectrum analyzer working, including a deep dive into FFT, are impressive.

[Ryan] wanted a spectrum analyzer for his audio equipment ... [Ryan] used simple resistor capacitor (RC) filters to implement his design. All those discrete components would quickly attenuate ...

For example, whereas an oscilloscope would show total noise level, a spectrum analyzer would show the noise as related to frequency. Available in both analog and digital models, digital analyzers ...