An electrical connector including a housing, a plurality of contacts fastened in the housing for mating with a plug, a plurality of terminals for connecting an electrical device, and a magnetic module electrically connecting the contacts and the terminals to form a number of signal channels carrying differential signal pairs. The magnetic module has a printed circuit board (PCB) and a transformer mounted thereon. The transformer is connected in one of the signal channels and comprises an H-shaped magnetic core, a magnetic board a primary coil having a first magnetic wire and a second magnetic wire, and a secondary coil having a third magnetic wire and a fourth magnetic wire. The wires have specific parameters to suit specific needs.