I have a 16 channel Yamaha mixing board. I need more channels...can a board be expanded to another and if so , how?

The best way to do this entirely depends on what you're using these for, as well as the model of each board.  Provide me with both and I'll tell you the optimal way to set this up.
orksecurity7 years ago
The closest you can come is to put another mixer next to it and feed the output that into one of the main board's aux ins. (Unless one of your inputs is already a line level signal; in that case, move that to aux in.)

If this is going to be an ongoing need, you may instead want to look at trading in your board and upgrading.
GARYF (author)  orksecurity7 years ago
Thanks for your input. I suspected as you did and I'm going to try it tonight.
Ideal, for purposes of keeping things straight, is if the sub-board's signals wind up in corresponding places on the main board -- that is, if in addition to copying the left/right busses over, you can also have aux1 on the sub-board wind up at the main board's aux1 outputs and so on. I believe some boards make this easier than others, by providing some additional line-level inputs arranged by bus, with just a trim pot on them.

BTW, check your board's user manual; they may actually have some recommendations on how to arrange this setup. (I seem to remember that the Mackie board I was using did illustrate a few less-common setups as well as the basic live sound/studio setups.