Help - Does my Virus Need a DI Box to take care of noise?
 

Hi - Greatly appreciate any advice/solutions here. The core system of my home studio is:
Mac G5 PowerPC dual-processor running Cubase 4.5
RME Audio Fireface 800 connected to the Mac via Firewire 800
Hafler Amp
Hafler M5 Reference Monitors

Anyway, I spent quite some time getting this setup quiet, isolating power cables from audio cables and the result is a very quiet setup with no obvious ground loop problems. For example, for all my instruments, for example my Oasys, I can connect the outs directly to the Fireface and have no residual noise, buzzing, clicking, etc.

However....I have this problem with my Virus TI Desktop. When I connect either the SPDIF out or the analog outs to my Fireface, I get a noticeable low-level digital-sounding noise. Not a hum, not popping, but a fuzz that is noticeable component of each instance of sound output.

What can I do about this - is this simply a need for a DI box (although aren't the outputs of the Virus balanced?) or is there something else I need to consider? And what about cleaning up the SPDIF signal?

This is actually pretty frustrating considering that I have repositioned the Virus all over the studio to try to get rid of this noise.

Thanks to anyone who may have some constructive suggestions!

CirclingKailas

One More THing
 

I also hear the same type of noise when just using headphones with the Virus headphone jack - is this a general grounding issue, and why would the noise appear in both analogue and digital outputs? The instrument is some distance from my Mac, so I am not sure it could be picking up computer noise.

Thanks

One More Detail
 

One more detail. The fuzz/noise only sounds when a note has been triggered in the Virus - and it sounds for the duration of the note. If no signals have triggered the Virus, then the unit is absolutely quiet. So, what could be causing the noise?

Thanks
CirclingKailas

does this happen if you the usb is connected?