Just so you are aware, if you are making sampling tech which needs to notch out 50hz and 60hz, if I remember correctly, Analog Devices makes a 24bit ADC which has an absurd built in 21 tap, or more, digital filtering processor specifically designed for that task to deal with AC emi and it's overtones. It had something like an insane 180db reject on those 2 frequencies.
I once designed scales for food filling machines which had to sample really fast, yet reject the food feed vibration beds which were controlled by the my electronic scale.
It just requires 1 crystal and it provides you a clock with a fixed sample rate. You can gang them together using only 1 crystal to create a huge channel sampling system with channel to channel perfect reject of those tones.