Very low volume in anoncements

Hello together,
I have a problem:
the Asterisk 1.2 PBX runs well everything works, but the annoncements / promts are very very low volume (background music works fine) nearly hard to hear and to understand.
Increase volume in the recording doesn’t help.
Another format the same ( I tried GSM, WAV, MP3 all the same)
On the Console => everthing OK volume quite good
But on Phone I find no way neither on Capi-Channel nor on SIP :unamused:

Any Ideas?