Summing box -How would you build it?

[XAXAU]

I'm a rookie in electronics and have after 15 years in the box decided to build a summing box to do all the things that ITB just cannot. Recently I've gone through a few analog synths and initially I though they were weird and unpredictable, but have now realized that the charm and vibe comes from just that. The saturation in the osc mixer, filter distortion, overdrive etc. it's so reactive. I'm a huge fan and avid user of distortion in my music making and mixing and analog is truly where it's at. I've gone through almost a hundred distortion plugins and although they sound good in their own way, they can't do what analog does.

So after research and listening tests I've gotten hooked on the API sound and the CAPI stuff is great. I want to build a 2-ACA-BO with Jeff's new Litz wire trafos and gar2520 DOA's.

The idea is to have a tube circuit in there as well as a tape sim. Gustav's heater or tube part of the pultec for the tube section and soundskulptor sts tapesim (with limiter mids) as interstage/ insert processors. It would be nice with Gustavs MS Matrice built in as well cause I like to tweak audio
that way, plus most compressor projects here is mono so the LR balance would not matter, hence no need for expensive elmas. MS with transformers is another option plus it will bring more trafo mojo into the audio chain. A switch for on, off & bypass (the trafos = less coloration if needed).

Is it stupid of me wanting to put all in one box? I realize the power supply's would be a major issue plus it'll be a huge project. My head says build the summing unit first and the other units later on.  Oh, and it would be cool to reduce the negative feedback on the output trafos like in the Neve silk circuits, but I have no idea how to do that!

How would you build it? What else would be nice to have in the mix?

Thanks guys!

 

[pucho812]

best summing box design I have ever used was handed down to me and is completely passive with an output of 200Ω roughly 46 dB down from line level.  The idea being i can add any pair of mic pres for make up gain to be back at line level.

I have been over this a lot and have come to the conclusion, Passive summing boxes do much. Mainly because I don't think resistors really change the sonics all that much as far a tone. To me all that happens on the make up side as each make up amp has it's own tone.  So a summing box output at 200Ω 46dB shy of line level is perfect  for any preamp on the market DIY or otherwise.

 

[analag]

I built a active summing box with one summing stage with output transformer configured to flip signal back into phase and also provide balanced buss insert. Summing and gain makeup amp was servoed for cleaner signal path. Gain makeup was again transformer coupled at the output. Gives me the big sound.

 

[JohnRoberts]

For a modest number of stems a simple virtual earth will deliver good (low noise/low distortion) performance.

The attraction of "passive" + gain stage mixers, is that the gain stage can add colorations that they like.

JR

 

[analag]

That's why I built in a buss insert to plug my various creatures in there.

 

[ruffrecords]

Shameless plug - my DB25 PCBs will do the passive mixing and provide a convenient interface. Just add the gain make up of your choice.

Cheers

Ian