as stated above. What are they for?
A child bus get the kids to and from school on time
they are “subsets” of a multi-channel input or output.
let’s say you have created a 5.1 surround channel (therefore, comprised of Left & Right front, Left & Right rear, Center, and Low Freq)
Normally, you’d want to feed a 5.1 source into that surround channel, but you could also send a stereo source into either the L&R front child buss, or the L&R rear child buss, and use the panner to place them in the front/rear spacial image.Likewise, you could create five mono child busses, and feed any one of them with a mono source, and place that anywhere in the spacial image.
As regards which version of Cubase, so long as it is the “full” version, if you create a a channel that is quadro or 5.1 etc., you can access “subsets” (i.e; “child busses”) of it.
So there is no point or use in using a child buss in a regular stereo mix?
There is one special case where it might be useful (or even necessary ) to set up a quad Group, even in a stereo mix… there are certain VST2 plugins that have sidechaining capabilities, which work by routing the main signal to L&R Front, and the sidechain “keying” to L&R Rear. Otherwise, if you don’t have a quad or 5.1 group or output set up, you wouldn’t be able to create a child buss anyways .