Excessive White Noise After Normalising Pro Tools 12

[hugh loughlan]

I have recently upgraded from pro tools 10 to pro tools 12. I have also replaced my Imac (previously snow leopard) to 10.10.5 Yosemite. I record audio books for acx (audacity). My set up is unchanged. I record in a home made booth through an interface (Avid Fast Track Solo). I have to follow specific steps to meet acx technical requirements. This is part of a mastering chain (Equalise, Normalise, Expand, Limit). I have previously followed this protocol without incident. Since upgrade the Normalise stage creates massive White Noise and is unusable. There seems to be very little help for pro tools 12 on youtube or other discussion forums. Any suggestions would be welcome. Thanks.