The Yamaha MG10XUF inputs 5 - 10 don't produce output on both speakers when I connect my guitar. Why is that? It seems to be the only analog mixer in the world to do this. The sound comes out of just one of the two speakers, every time I connect my AC guitar in the 5, 6, 7, 8, 9 and 10 inputs of this mixer.
How can I fix this, please?