It varies by dialect and by level of formality. -au is pronounced /-au/ in many settings, and it is the 'standard'. In informal speech it sometimes tends to shift to /-a/ in north-west and south-east Wales, and to /-e/ elsewhere.
The -au spelling at the end of words only became the usual written form about a century ago following publications on the grammar of Middle and Modern Welsh by John Morris Jones. Before that it could be -au or -eu depending on the word and possibly on the writer.
The pronunciation of this word that I hear on my desktop and my phone sounds fine. The usual pronunciation of /au/ is also explained very well on the videos referred to in the notes to Greetings1 at the start of the course (http://www.duolingo.com/comment/13186004)
Remember that local pronunciations may change across the 5 main dialect areas in Wales, but the 'standard' pronunciation can always be understood.