Designing a summing Mixer. Help wanted.

also, there are a thousand and one summing mixer projects in progress or completed over at GroupDIY.com

It seems simple from the outside, but experience with console manufacturers and design in the past leads me to believe that there's a lot more to it than meets the eye. It would no doubt become an all consuming commitment. My $.02.

This could be a grassroots project. Instead of you footing the bill for parts and R&D Cary, it could be something everyone got behind and pitched in on to make happen. In the end everyone would get be given a BOM which would include the PCB's. You could either build it, or have one of us who's into DIY heavily build it for you for a cost. If we were talking about a compressor, or a D/A etc. I wouldn't suggest this, but, we are talking about something that almost near everyone needs. Something like this could be funded quickly and it could also be done quickly if it were set up this way.

I have some ideas on a signal flow chart that I work on from time to time on what I think would be the perfect summing rig. It's not finished but it's nearly. If this were to be something like a grassroots effort everyone who chooses to participate could create their own signal flow charts, placing whatever you think would be the perfect summing rig and at the end we can take the best of the best, through polls and then come together to see if any users features could be combined with other users features. Then you'd have a final vote on say 3 options and go with the winner. At that point, money that's in the pot could be paid to someone we all approve and have them draw out the schematic and board design, unless there was a designer on the list that was willing to do the design at no cost to help the cause.

Everyone would have to understand going into it from the beginning that the final design could be costly in parts, or if you choose, labor. But, you would have that BOM and PCB's to slowly piece together your kit.

Just an idea.

If you're just thinking about passive summing then yes, there's tons of it, it's simple and can be done with a handful of resistors and wire. I know what I'm talking about is building a complete unit that features summing section but with an output section that works together with different stages to give the outputted program material the feeling of being mixing through a console, and a damn good console. There are some things that have not been done yet, some ideas that no one has put all together. It can be done, I'm with Cary on this, I'd love to see an all in one summing rig that made it possible to be hybrid and get that console feeling completely. it's all in the back end and creativity and quality components will get it there.

So I'll add a few things.

All summing is passive at the point where the signals are mixed, the summing resistors.

Active summing is simply a passive summing network with gain afterwards.

You have a choice of voltage summing(non-inverting buffer) or current summing(inverting virtual earth), each has it's drawbacks.

Non-inverting buffer drawbacks: Poor isolation, adding/subtracting channels causes level changes, higher summing resistor noise, more channels added to the bus need more gain.

Inverting current summing: Good isolation, no level changes with addition and subtraction of channels but noise gain changes, less summing resistor noise, needs extremely good grounding for noise immunity, needs opamps capable of high currents.

With so many designs already out, seems like a re-inventing of the wheel. I like phase reverse, filters, EQ, routing, sends, a fader I can ride and, oh wait, all that extra stuff is called a console.

With quality used recording consoles selling for 5 cents on the dollar or less, a sum mixer project seems like a short loaded money pit with unpredictable results.