HI MArtin,

> The big task/problem,that will be my adventure,is to see how a cable
> can do a mix/summing of to signals. Seems logic to me, but also
> somehow like a child´s idea... hmmm.

There is no problem at all: I checked the owners manual and there is no
need for mixing. http://www.nobels.com/oman/mv-c_ownersmanual.pdf says:

"
[...]
2 ) If OUTPUT B is not connected the signal of
channel B is switched to OUTPUT A.
3 ) You can mix two different input sources to
OUTPUT A.
[...]
"

Florian