We had some trouble creating multi-channel WAV files for use with a Motu 828 MK2, so after finally figuring it out, I thought I'd post the settings in case anyone else also has problems. We tested this with 8 channels of audio through a PB Server Pro running build 4254, using Audacity 1.3.11 beta in Windows XP.
1. Use Audacity 1.3 Beta! - Version 1.2 is NOT ABLE to export multi-channel WAV files.
2. Select Edit, Preferences, choose the Import/Export option. Select Use Custom Mix.
3. Set the Project Rate to 44100 Hz using the dropdown box in the bottom-left of the screen.
4. Set the sample rate of all tracks to 44100 Hz.
If working with existing files, select all tracks, then select Tracks, Resample.
If working with new files, set the default sample options in Edit, Preferences, Quality.
5. Set the sample format to 16-bit PCM.
If working with existing tracks, select the Dropdown Arrow, Set Sample Format.
If working with new files, set the default sample options in Edit, Preferences, Quality.
6. To export, choose File, Export, and Save as Type: Other uncompressed files. Then, select Options, and use the WAVEX (Microsoft) Header and the Signed 16bit PCM Encoding format.
7. Click Save, enter Metadata if desired, click OK, double-check your “Advanced Mixing Options” to make sure each track is mapped to the correct channel number, and click OK again.