When I made a multichannel digital delay line in 1985 (12 bit sampling
At that time we made FFT spectral analysers for 1/f noise measurements in semiconductors. It was a serious r&d so when people are connecting something to arduino and do FFT today is funny to see
We spent months with decoupling, denoising, optimising our low noise preamplifiers, high order low pass filters, adconverters (at that time a discrete construction - DAC, successive aprox reg., S/H, comparator, etc) so we had a lot of control over it. We needed a lot of FFTs to make (and a lot of math, the spectra precision is related to sqrt(N), where N is number of FFTs done) for a single spectral plot - quite a time consuming exercise at that time
