And, BTW. I've noticed that this place compresses original images even further, that's why the image in my previous post is not as clear as it should be. Here's the original, attached in a ZIP file so you can download it and see it with a little better resolution.

Thanks!

 

Your "audio" circuit in the other thread uses a 0.1uF input capacitor C1 driving the low resistance R9 of 1k ohms at its input.
Then it cuts all audio frequencies below 1600Hz. Audio frequencies go as low as 20Hz so you are missing about 6.5 octaves. Audio has a total of 10 octaves so more sounds are missing than you pass.

A capacitor driving a resistance is a highpass filter that cuts low frequencies. The formula for the capacitance, the resistance and the -3db cutoff frequency is simple: f= 1 divided by (2 x pi x R x C).

 

Your "audio" circuit in the other thread uses a 0.1uF input capacitor C1 driving the low resistance R9 of 1k ohms at its input.
Then it cuts all audio frequencies below 1600Hz. Audio frequencies go as low as 20Hz so you are missing about 6.5 octaves. Audio has a total of 10 octaves so more sounds are missing than you pass.

A capacitor driving a resistance is a highpass filter that cuts low frequencies. The formula for the capacitance, the resistance and the -3db cutoff frequency is simple: f= 1 divided by (2 x pi x R x C).

I understand what you’re saying. Perhaps I should rename the other thread “Signal Output Derived from Variable AC Input” as it has little do do with audio and more to do with tracking a variable AC signal amplitude.

Practical tests have shown that the cutoff of these frequencies has had no undesirable effect on the circuit.

However increasing the 1K resistors to 10K decreased the cutoff frequency and had no negative effect. So thanks for your explanation.

I want to amplify a signal before running it through a peak detector, so that is easy to divide the input into four windows of varying sizes.