[jacquesm]

> I have found better ADC chips than the ones that come pre-soldered on most EDP32 dev boards (and have breadboarded them up with success).

Depending on your setup: beware of your ground and realize that breadboards are an extremely bad fit for this sort of application. It's hard enough to get maximum performance out of a good DAC on a custom designed PCB, on a breadboard it can be a nightmare.

[JKCalhoun]

The breadboard has validated the communication between the ESP32 and ADC chip (over I2C).

It's enough that I've now moved to KiCad layout and will wait for the boards to come back to see if the actual ADC data I am getting is more or less linear, noiseless…

[jacquesm]

Ah ok! Thanks for that bit of clarification, it makes a world of a difference, yes, you can use the breadboard for that, but - based on my own experience - if you want to actually use an ADC on a breadboard you're going to be in for a world of hurt as soon as you exceed some very low threshold frequency of updating and you're going to be fighting all kinds of weird bias effects. The parasitic capacitance of those breadboards is just terrible.

[elictronic]

Large metal planes uniformly spaced. At what point is the parasitic capacitance just a capacitor.

[jacquesm]

And an antenna, and a coil. Breadboards are great for slow and digital up a few 100 Khz, above that you are going to have the occasional interesting challenge / hairpulling session.