TSH82 - Hacking the board

Hello.
I did little modification on the board, change R7 and R8 to 10kohm resistors, so obtain unity gain in first stage.
Paralell to R7, following Hookup Guide, I use a capacitor in C4, something like 2.2nF expecting to obtain a low-pas filter with cut-off frequency of aproximatelly 7kHz.

The unity gain was observed in the whole bandwidth, but not action of a low-pass filter.

From 1 to 10kHz I observed a reduction of a senoidal input as expected, howerver in frequencies up to 20kHz to 1MHz the reduction of amplitude was almost half from 10kHz and remain constant, when I expected to reduce to something near 0.

The main issues are that the board design was engineered for the electret mic’s range (100Hz-10kHz) and while your calculations are good the real-world performance of components can become a huge factor…you can overcome this pretty easily by adding a 2nd-order active filter; Perplexity.ai had a really good response for this https://www.perplexity.ai/search/hello-i-did-little-modificatio-4QSvCgIiTb2iUnx9zwqR0A#0 that covers most everything