Also had this issue on output 2 of a DH2G-D - solved it by using some DA's in-between. Think its an earthing issue with the TH2G & DH2G Digital editions. That said, not all the DA's I tried worked either...

Also - if you're trying to use a TH2G-D in Dual Head mode (as it states on the documentation) - it wont work on a mac... only PC

S