Shielding or even guarding high impedance parts of the circuit (if such parts are needed), buffering high Z inputs as close to the input as possible, using bypassing capacitors to power the chips with high Z inputs and pull up/down resistors (when they could be used), filtering Vcc before passing it to sensitive parts can protect circuits from nearly any interference, including 50/60Hz.
I never have 60 Hz problems.
Now, 50 Hz, that’s a different story.
Means you can’t be sloppy in your design and construction.
Shielding or even guarding high impedance parts of the circuit (if such parts are needed), buffering high Z inputs as close to the input as possible, using bypassing capacitors to power the chips with high Z inputs and pull up/down resistors (when they could be used), filtering Vcc before passing it to sensitive parts can protect circuits from nearly any interference, including 50/60Hz.
i once was building an amplifier with lm1875, and when i touched it on the breadboard, i could hear an FM station in the speaker
I’ve had oscilloscope sessions where the measurements depended on whether the fluorescent lamps on the ceiling were on or not. Lots of fun to debug.
In europe its 50 hz…
I’m working with ECG signals right now and the mains noise kinda wrecks havoc with my output 🙄