# Buffer, amplify, filter, sample - In which order?

I'm trying get an audio signal from a high impedance source (guitar or mic) to an ADC.

Some casual research suggested that I should filter my signal before amplifying it.

My current mental design is: Source -> Buffer (optional depending on impedance) -> Butterworth filter -> Boost -> ADC.

1. Is this the "correct" way to design this circuit?

2. Does it make sense to throw in an RC filter (or a second active filter), e.g. before the ADC?

• considering potential interference yes to above and possibly CM choke – Tony Stewart Sunnyskyguy EE75 Apr 2 '18 at 21:05
• Yes to both questions? @TonyStewart.EEsince'75 – tiftik Apr 2 '18 at 21:27
• It could be combined into one circuit that buffers, filters and boosts gain remotely and consider with large CM choke for improved balance. PS noise than is common mode is often hard to track down and eliminate – Tony Stewart Sunnyskyguy EE75 Apr 2 '18 at 21:56
• Transducers (mediates between some physical phenomenon and electrical signalling of some kind) often require some kind of specialized circuitry that maximizes some desired parameters. For example, a guitar uses variable reluctance and the magnitude of the signal is $\propto$ velocity. So, one may need to design a pre-amplifier (though many do not so) that provides the right frequency pre-emphasis as well as handling the details of the type of input well. So the first step would be to design a circuit tailored for the type of input device. Noise may drive choices in the design (JFET vs BJT..) – jonk Apr 2 '18 at 23:32