Time for a new thread on the Avast Firewall DPC latency issue. This has caused many users to ditch the Firewall but there has been several fixes and will continue to fix.
There has been some fixes in 17.2 which have made the issue happen less intermittently.
This usually makes the audio stutter on videos and/or crackling sounds to name some symtons.
It is still happening though and if anyone can help how they can reproduce the issue while showing stats from DCP Latency Checker (http://www.thesycon.de/eng/latency_check.shtml) with and without (that means removing the Firewall) not disabling!
A simple test would be running a Youtube video on the browser then looking at the DCP latency, removing the firewall - reboot, run same video again and compare the difference. This would be particularly helpful if you are doing it while audio is stuttering.
If you look at the screenshots, the spikes in red are the ones to ideally look out and report.