What is the best method to let the voice quality through Dahdi channels to be clear and no echo? Is it the wanpipe or it is working only with sangoma?
Asterisk uses “echo cancellation” to enhance audio. EC can be done in soft- or hardware. All major card manufacturers have variants of their cards with hardware echo cancellation support. Searching the internet gives a lot of information about this topic.
If you install a Sangoma card without HWEC, then you do get the default software canceler. Depending on your needs, switching to the OSLEC
canceler might or might not be a better choice. Generally, a card with HWEC gives the best results, especially when you also have a lot of facsimile messages.