For years I've used a Behringer 1204 small format mixer on my desktop for simple monitoring and routing while mixing and recording. For years I have been frustrated with the lack of features and I/O options. After a recent episode of frustration involving the dual function of the mute switches and Post-Fader axillary sends, it occurred to me, why not just build my own mixer? How hard can it be?
Well to those of you still reading and not rolling on the floor laughing at this previous statement, it requires a bit of thought and is by no means a simple, weekend project. There are many design topologies to consider and many variables to account for. One of my greatest resources (aside from the endlessly helpful book The Art of Electronics) was a project published by Rod Elliott (http://sound.westhost.com/project30.htm). His designs provided answers to many of my questions, such as how to implement a panning adjustment and peak level indicators. Of course his designs are very similar in functionality to the mixer I already have (though he does include insert sends and returns). What I want in my mixer are tape returns. I want an entirely separate signal path for the monitor return of each channel. Typically this feature is only available in high-end studio consoles. Well, I don't have that sort of money, so I want tape returns in a 10 channel format, plus direct outs.
I've included my first revision schematic bellow, after the board layout is complete I plan on getting a handful of boards printed commercially and doing a test run with the component values I've specified thus far.
