RCD 510 with AUX issue

[mance23]

Can anyone help me, I fitted my AUX cable to my RCD 510 yesterday. The sound is very low and poor quality. Now somehow I pushed the AUX button maybe twice or 3 times on my unit and it switched to "CD7" and instantly the sound was as good as a CD  . Does anyone know how to get this feature back ? the cable i am using is listed below

http://www.ebay.co.uk/itm/VW-AUDI-SKODA-SEAT-IPOD-AUX-CONVERTOR-LEADS-2004-RCD300-RCD310-ETC-/140653611328?pt=UK_In_Car_Technology&hash=item20bf9bc940

Thanks Guys