Maybe you can clarify what setting / changing / toggling the host computers sample rate exactly means? RME settings of the soundcard connecting the converters to the camputer? or are we talking about the sample rate of the DAW?
This means the sample rate of the H9000 USB Audio device, found in the Audio MIDI Setup pane (assuming you're on a Mac). If you're using an aggregate device, setting the sample rate on the aggregate device should also affect each individual device, but it might be worth checking the H9000's tab to make sure this is the case. In most DAWs as far as I know, setting this in the IO setup in the DAW is also the same as setting it in the Mac control panel.
The H9k is set to Word clock and seems to acept that setting, as it deos not switch back to internal clock after a few seconds. This should mean teh clock is locked, correct?Show More...
I may have been wrong about this functionality, as I think this behavior was changed at some time in the past. Our next software release (due out in the next few weeks) has much better indication of clock status, sample rate, and USB driver status in Emote. But I think that, if the clock is propagating to your other devices correctly, this is likely not the issue.
You could try simplifying the setup a bit to isolate what the potential issue might be – using the H9000 as the master clock and USB as the sole audio device to confirm that works – and then building back up the setup piece by piece. We've never tried aggregating our USB audio device with a Firewire audio device in the same setup, but see no obvious reason why it shouldn't work.