Adding EQ control to Obsidius

[Mothman]

Hi, I want to put an eq control for the obsidius, I am thinking in putting it right before de volume stage. Do I must put it before R25 (on diagram) or before IC 4.1?

 

[Chuck D. Bones]

IC4.1 & IC4.2 are active low-pass filters. You could simply replace one of the resistors R23 - R26 with a pot + resistor to get a variable EQ. That's what I would do. If you want to insert a BMP-type EQ, the best place is between IC4-1 and the LEVEL pot. What type of EQ do you want? This thing already has a mid-scoop.

 

[Mothman]

I want to try adding this eq with some mods

 

[Chuck D. Bones]

You can do all that with one opamp. Take a look at Chela's EQ for an example. You could even hi-jack IC4.1 for that purpose.