Hello !
Using X100P for 2 years long… the sound quality was not to good, on zttest got 95,XXX-98,XXX
So I changed on another IRQ with APIC.
Now I have cristal clear sound, and zttest is 99,7XX-99,99X, but now I have anather problem 
Kernel 2.6.23.9
Asterisk 1.4.15
Zaptel 1.4.7
When calling throu a Zap channel (X100P) I got a big delay, 40-50% of the time.
Executing [021XXXXXXX@payphone:1] Dial(“SIP/1002-08213550”, “Zap/1/021XXXXXXX|60|Tr”) in new stack
- sometime its block here, and on the FXO line I can here busytone
– Called 1/021XXXXXXX - sometime the delay is here 3-20 seconds, the FXO line is allready ringing the corect number, the person answer but can’t here me, I can’t here nothing over the other side of Asterisk, until Zap channel answer…
– Zap/1-1 answered SIP/1002-08213550 - now I can here…
The same problem when I receive a call…
Sometime is just working normal.