[Freeswitch-users] IAX outbound trunk and distortion

Hi, Just setup an IAX trunk from FS to a SIP provider who runs Asterisk, but getting a truckload of distortion when I make calls. The iax.conf.xml settings are as per the default. I've turned debugging on but just wondered where would be a good place to start trying to track down the problem? The codec appears to be PCMU/8000. Any suggestions welcome - this is the first time I've used IAX on FS, and have never had audio distortion issues with SIP trunks etc. Thanks, Alex