asterisk users - May 2005 - Unchanged sound through Asterisk

Hi!

To me, it seems like Asterisk are involved in alternating the sound/voice
running through it.
One thing is that it mutes DTMF digits.
I also got an Adit 600 channel bank connected via MGCP, which _might_ have
something to do with it,
but I can't find any settings in it, regarding DTMF mutes.

How can I make sure Asterisk is _not_
"changing"/"transforming" the sound (as muting DTMF etc.) in
any way?

Thanks!
--
Daniel