Hi,
Well sadly Kmix is unusable here, over time it just drags my machine to a crawl so I have disabled it :-(
I did some searching for an alternative and came across pnmixer in fedora's repo's, it is an old version old and limited but does the job that I use Kmix for.
I did try and build an RPM for the current version that has more features but it threw up a error about something defined in DSO and try adding it to the linker... I'd need to read up on that one..
https://github.com/nicklan/pnmixer/wiki
Cheers
Colin