'Endless Summer' DIY Analog Summing Mixer

Taking 8 outs from your interface rather than 2 will sound cleaner because each stem (pair of outputs) will be lower level and overload the D>A and output circuitry less.

It's an easy build but requires a complete change to your mixing workflow so it's not for everybody.
 
I'd like to hear what this thing is capable of too. That price is outstanding, and if it really does something nice to the audio this would be a no brainer!
 
No transformers = no point to me but to each his own.

Yep. But I also think summing in general isn't a great idea, unless it's strictly for workflow (adding outboard eq/comps etc).

Said it 100 times, summing isn't the amazing mix tool that people make it out to be. It's subtle...very very very subtle. 1db of eq on your master buss will make more of a difference tonally.