Low volume on certain phone calls

Hi Guys, This is my first post on this forum, I am also new to the Asterisk World. Here is what I have:

1 Asterisk installed on a centos distribution on a Lenovo PC
1 Grandstream Device 8 ports FX0
1 Linksys SPA-3102

Total lines in the server with these devices are 4 including 2 of these four that are vonage and magicjack adapters.

Computers with Zoiper Installed all on the same network where the server is located.

The problem relays on sometimes agent makes a call and the other ends sounds really low, even with speakers and maximum volume, also sometimes they caller would say that they can barely hear the agents voice.

Is there any way or route to start diagnosing what the problem could be ?

Thanks in advance for your help.


Contact the vendor of your FXO gateway; see if they can offer any suggestions.