Using shielded twin core cable is recommended:
In this situation the audio signal ground is carried by a dedicated line, which signal current, being separated from the shield, can not easily be interfered with by the shield’s noise currents caused by external interference. This advantage especially counts when low (e.g. microphone) signal levels are being transferred and/or long cable lengths are used. (With shielded single core cable on the other hand, the noise signal built up across the shield effectively is in series with (i.e. adds up to) the audio signal).
Furthermore, in connecting the shield to ground only at one side of the cable and lifting it at the other side it functions as a true screen: It does not carry any audio signal; It screens the inner conductors and drains away unwanted noise to one location