Legacy Cardas Quadlink

Can anyone explain the difference between the Quadlink and the Quadlink 5-C? Either in construction or sonic differences. Thanks.
Sorry I haven't heard the two to compare, but I use the 5-C and have stuck with them for many years.  I had swapped them out for Golden Reference and went back to the 5-C.  These are balanced only, I do not have any speaker or single ended.  I'm thinking the regular Quadlink are older versions.  But this is 10+ years ago.  Perhaps this will help.