What encode settings do you use when encoding to vorbis?
To be even more precise, we are currently using beta 5.
More info:
http://wiki.hydrogenaudio.org/index.php?title=AoTuV
http://www.geocities.jp/aoyoume/aotuv/
Starting with C75, the new beta 5.61 of aoyumi's Tuned Vorbis, or aoTuV, will be used.