Distorted echo inside the network on FXO channels

this thread is being discussed in >>> DAHDI audio problem with analog OpenVOX A400E FXO card

UPDATE:
after much coffee, sweat, and hair pulling i fell on this amazing post >>> http://kb.digium.com/articles/Troubleshooting/how-to-basic-fxotune

FXOTUNE ROCKS! problem solved just like that!