Topic: Why does Software Playback channel clip if Cubase master buss doesn't?

Hi all,

I feel perplexed and perhaps my issue is just some silly oversight:

I am trying to complete mastering a track.
In attempting to squeeze a few db  (maybe 2db) of gain by implementing a final limiter on the Cubase master buss, I find that the Total Mix software playback channel (1/2 which is receiving it's feed from Cubase) is clipping and distorting? Why is this? Surely it should really reflect the final level received from Cubase since Cubase is the only audio feeding to it? For the record, I am trying to peak at -1dbfs in Cubase. Without no limiter, peaking a few db lower everything is fine.

Thanks in advance.
Nolan