asterisk users - Jan 2005 - wctdm and alaw audio quality problem

I have a digium tdm40b (4fxs modules) with latest zaptel CVS modules
using the default ulaw codec the audio is good.
Forcing the alaw=1-4 option (zaptel.conf) with the same configuration 
the audio is really bad.

Has someone else the same audio problem?

/etc/zaptel.conf
loadzone = us
loadzone=it
defaultzone=it
fxsks=5
fxoks=1-4
alaw=1-4