summing bus... again... (but schem in french)

[Gulistan]

i've found a scan of some old french articles about studio tech articles.
One of these talk about balanced signal.

here are two schematics: (i have pcb too... but bad quality)

unbalanced to balanced (channel out)

summing, master volume and balanced out

what do you thing of this...?

 

[rafafredd]

looks like a very nice and simple active balanced mixer circuit!