Passive Summing Mixer & Channel Strip Ideas

I have been toying with the idea of making myself muliti-functional box for my simple home studio setup. At home I usually only do overdubs and mixing. I am already in the beginning stages of building myself a 2 ch api 312 pre, but I would really like to have a good summing mixer as well as a stereo EQ for mixing. My idea is to build a box that can function as a 2 ch pre while tracking that includes a passive summing mixer and passive stereo program EQ section (pultec) for mixing, with the 312 pre doing the makeup gain. I guess it's sort of a similar idea to the Shadow Hills Equinox minus the talkback and monitor section and with an EQ. I am not sure how difficult this would be. I imagine it would be a lot of switches or relays, but otherwise pretty straight forward. Any ideas, comments, suggestions?

I have had similar thoughts, but in the end, perhaps it is better to have these things in seperate boxes, and use good old fashioned cables to configure them for different uses? So you build three boxes:
-API312
-Pulteq-ish EQ
-Passive Summing Mixer

Link them in different ways for different jobs...

That way if you are going on a recording gig you don't need to lug around your 'Summing EQ Mic Pre Mixer', just your Mic Pre box.
Just my thoughts. Cheers!
-Mike C

Hey guys,

There's a ton of examples of this already on the board.  No need to reinvent the wheel.

Look at http://www.groupdiy.com/index.php?topic=16013.0 in the meta.  You will see the summing box.

Essentially, for a passive summing box - you will use resistors for each input.  This will cause a gain drop which is made up by whatever preamp you want.  You may to consider switched inputs on the 312 so you can set them the same volume. 

In terms of EQ, I would just run this after your gain makeup.

So... you can build a box (like lots of people have) with inputs with in series resistors (values for various ideas are on the meta) and then that sums to a stereo output.  Run your stereo output into your preamps and away you go.

If you want to just use the preamps - unplug the summing box.

Here's a schematic as well from Joe Malone that will assist.

http://www.jlmaudio.com/JLM%20Passive%20Mixer.gif

Good luck!

CC