raw is what asterisk wants. Here is the setup:
Asterisk/Allstar expects the file extension to be .ul or .ulaw.
The latest version of Asterisk will put .raw as the extension even if you specify something else.
You will have to re-name the file to end in .ul before you copy it to Asterisk. It didn’t used to do this. A revision about 6 months ago started forcing the “.raw” extension.
Ken