Those plugs are COMMONLY called "RCA" plugs. They are coaxial (two conductor) and one has to be a bit careful when soldering so the heat doesn't melt the insulation of the inner conductor. Strip the outer insulation back and then carefully unbraid the braided condutor. Sometimes one can use a suede brush or use a sewing needle to open the braid. This solders to the outer shell. The inner conductor pokes through the end of the plug and a drop of solder attaches it. Those plugs are COMMONLY called "RCA" plugs. They are coaxial (two conductor) and one has to be a bit careful when soldering so the heat doesn't melt the insulation of the inner conductor. Strip the outer insulation back and then carefully unbraid the braided condutor. Sometimes one can use a suede brush or use a sewing needle to open the braid. This solders to the outer shell. The inner conductor pokes through the end of the plug and a drop of solder attaches it.