I'm back here, again struggling with this simple circuit: apologies.
I'm going to attach once again the reference circuit to simplify everybody's life.
Please remember my frequency range of interest is very low, between 50Hz and 150Hz.
The circuit is using capacitive coupling which represents an issue with low frequencies acting as an high pass filter. One example of such limitation is C1 which with 100nF presents a corresponding reactance at 50Hz over 3kΩ causing an impressive voltage drop of my input signal: I'm going to replace it with a 10μF capacitor (32Ω at 50Hz => 80mV drop), but I'm seeking advice for a better solution on this side. The same issue is presented by C4 on the other side.
With a bigger capacitor I'm able to get some decent signal into my amplifier, but such capacitors are correspondigly big in terms of size (I'm using polyester capacitors).
I believe my only choice is to avoid the DC decoupling by using direct coupling, but I think to move further along this route I'll have to abandon the TL082 opamp and move into one of the suggested ones.
I've got a LM386 and a LM358 to play with while I wait for the MCP602 to reach this corner of the world: by reading the datasheet it seems the LM358 seems a better fit with its single low voltage supply.
