Hi everyone, I recently bought a Technics SU-X101 amplifier and I'm happy with it, but there's connection on the back I can't figure out. Next to the speaker outputs there's a pair of phono/RCA sockets which looks very much like an extra phono line in/out, only it's labelled ''Surround'. I'm assuming it's something related to adding more speakers but I don't know how. Perhaps to go to a second amp, or active subwoofers...? Is anyone familiar with this amp, or with this kind of connection? Thanks guys.