JCM 800 Mod question

[Tubis]

As i say further down in the thread, i dont know the exact math for this but the simple 1/(2*pi*C*R)wont work here. If you trye this in a spice simulator that has a bode plotter you can se this. And if you slap a 10nF over a 4k7 you will hear it as well IRL. A simple but not completely accurate math is to take the math youre doing and divide it by ten. One should also have in mind that the cathode bypass creates more of a shelf filter than a highpass filter.
An example is the 2203 input stage of 680nF over 2k7. If you use your math that doesnt explane the freq.response youre getting.

[Tubis]

I must apologize, I dont know what went wrong in my head but I thougt it was 10nf but I realise its 1nf. That flips everything I said to ten times higher frequensies, sorry about that.