I have a noticeable delay when I talk via my voip provider (CallCentric) but not via PSTN. I have been reading the forums to find the possible problems and have tried to disable the option "PBX delivers audio' but this does not seem to make a difference. What exactly does this option do (on the VOIP provider advance tab)? Are there any other suggestions to try. I would estimate that the delay is about 500 ms.