The input cutoff and output cutoff add and produce -3dB at about 150hz and -3dB at about 80Hz. If you want a -3dB total cutoff at 50Hz then both RC cutoffs must be 25Hz.I'm not quite understanding what needs to be calculated here. In your sketch where theres 30Hz cut-off freqency on the Preamps input. Does that freqency need to be lower than 30Hz or does this freqency stay at 30Hz but adds to the capacitor on the output of the Preamp capacitor which feeds the input cut-off freqency on the Power amp and the headphone amp cut-off freqency to total to 50Hzs as you suggested...
the feedback capacitor is too big at 22uF so it has no effect on the total cutoff frequency. Even if it is 10uF then its cutoff frequency is so low (7.3Hz) that it also will not affect the total cutoff frequency.What about the feedback cut-off freqency. How does this frequency play into the Preamps output capacitor?
If you make the input capacitor, output capacitor and feedback capacitor all with a cutoff (-3dB) at 30Hz then the total cutoff will be -9dB at 30Hz and 30Hz will be at a fairly low level. If you make then all have a cutoff at 16Hz then the total cutoff will be -3dB at 50Hz that you want.Does the feedback capacitor need to change? If I change the 22uf to 2.2uf which will give a cut-off freqency of 32.88Hz on this feedback circuit instead of 3.3Hz. Dose this freqency change an adds to the 30Hz thats on the input of the Preamp. I'm Totally confused on this. Help!
But if the feedback capacitor is 10uF with a cutoff frequency of 7.3Hz then it won't affect the total cutoff so the input and output capacitors can have a cutoff frequency of 25Hz then the total cutoff is -3dB at 50Hz that you want.