No, the sleeve is normally ground, and the signal is normally the tip. The ring is used to connect the battery to ground (the sleeve) when a non-stereo plug is put into the jack, since both the sleeve and ring contacts touch the same piece of metal on a non-stereo plug.
Yamaha RBX270 (mfd. by kaohsiung Yamaha Ltd, Taiwan) D'Addario EBT92s, Peavey TNT130
Blessing Artist metal pneumatic piccolo fretless bass (that's a trombone, folks ;-)