Horrible audio quality with X-Lite on OS X

[slamb]

I'm using X-Lite 2.0 release 1103m build stamp 14266 on Mac OS X 10.4 Tiger.

The incoming audio quality is awful! It sounds horribly distorted. I've tried different codecs. I'm connecting to a local Asterisk server, so I can't blame the Internet. ulaw on X-Lite sounds much, much worse than ulaw on iaxcomm 1.0rc3. It sounds like the type of distortion you'd get from maxing out the volume, but it's not that loud.

I'm wearing headphones, so it's not microphone feedback. In fact, it happens when listening to Asterisk's musiconhold, which completely ignores my audio input.

Is there a setting somewhere that I'm missing? The only potentially relevant setting I've seen is "Use Speaker AGC". I've tried it both ways.