I understand you are experiencing issues with your A30. Here are a few steps you can take to attempt to remedy the issues.
Make sure the inline mute cable is plugged completely into the headset MixAmp. You should be able to feel the cable click into the headset and MixAmp firmly.
Unplug the headset from the MixAmp and plug it directly into an Ipod or Mp3 player. Check and see if your audio quality is the same or better.
Plug a different headset into the MixAmp (Any headset including ear buds) check to see if the audio quality is the same or is improved.
If these steps did not alleviate the issues you were experiencing, or if you have narrowed down the issue, please go to the link below and submit a case. Let your agent know all the steps you tried and the outcome of your troubleshooting. It will help speed the resolution of your case!