Probably you seen topic "ILiad is making noise!" on iRex forum:
http://forum.irexnet.com/viewtopic.php?t=481
I also found this problem and I took old sound cable and did stub. I has sawed metallic jackplug and filled *external* side with white varnish and it looks very well. Jackplug should be metallic inside, but external side which you see on the photo should be electrically isolated (e.g. white varnish).
Please look on attached photos.
No noise any more.
And probably it will increase time of batteries.