Ludwig Phase II filter section

[Earthscum]

I've been playing with different variations of filters lately, and some of my ideas made me keep going back and pondering the LPII filter section, and how it works. Well, today I decided to stare it down, and I think I won...

So, I hope some pros will step in and fill in the details, but here is the basics of how the Phase II filter section works (one half):

The signal enters through the base of Q10, which acts as a phase splitter. The non-inver5ting signal goes out to be mixed, and the inverting signal  drives the base of Q11.

Q11 in turn drives Q12 and 13. Q13 has a Pi Filter consisting primarily of R50, C21, and C22. This causes a high-pass response at the output of Q11/Q12.

The signal then enters into the base of Q9, which drives Q7 and 8 in the same manner, forming the second stage of a high pass filter, which then directly feeds the base of Q10, causing a 2nd order Low Pass filter to be formed, which is realized at the non-inverting output of Q10.

Here's a basic diagram:



I'm off, back to work. Looking forward to further analysis by others. Enjoy!

[Keppy]

I never saw this when it was posted. Apparently, no one else did either. Bump!

[pinkjimiphoton]

hey rg, can you translate this into english my stimpleton like mind can understand please?