[sdiy] Final-stage mixer module?

[David G Dixon]

> I'd like to make a simple (TL07x) mixer for the final output 
> of my modular. I want it to block DC. I recall seeing a 
> schematic that showed two electrolytics back-to-back to 
> achieve this. Is it as simple as that? Or is it better to 
> have small ceramics on each input instead?
> Both?

To block DC but not filter audio, you'll want some pretty big caps.  I've
used 10uF non-polar electrolytics or regular 22uF electrolytics
back-to-back.  I prefer the former because it's smaller on the board.  I'd
probably put one on each input, and them sum, and then reinvert.  A TL072
will work well.

Others may give different advice or think I'm smoking crack.  Experiment!