Impedance issues with filter project.

M

Morbidpale

Well-known member
I have been working on a dual filter pedal. Something very out of my wheelhouse. I liked one channel of the DBA Sound Saw so I started learning about notch filters to create a second channel I liked. The circuit needed some more volume and I wanted to stay with the reverse beta theme the circuit already had at the end. BUT i have terrible input impedance (I learned how to test that, this has yielded lots of new information). I want to place this after my dirt pedals so...

How can I fix my impedance issue?
Are the reverse beta stages the problem?
Can I work around that?
Am I in Jack Orman Pickup Sim. territory now?

Sprinkle Filter-1.png
 
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I’m just throwing some ideas lifted from recent reads with pedal stuff and deeds with tube amps. Nothing technical, but hopefully practical with some adjusting?

  • Tone stacks can be considered as lossy for gain. For this reason a cathode follower stage is usually used before tone stack in tube amps to make gain loss smaller. Regular and boring emitter follower stage before tonez controlz?
  • Try darlington transistors for q1&4. Higher input impedance and more gain out.
  • Jfet input like in DBA Germ filther found in Boneyard page two. More invasive solution for sure.
  • Buffer stage before q1? But I already said it first! Buffer dat.
 
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