Buzz from Eleven Rack into PT 12

[BuddyReklam]

Hi Guys-

I have begun getting a slight buzz on all of my 11 Rack patches when recording into Pro Tools - I am running HD 12 via an Omni- best described as a relatively high pitched buzzing that is noticeable only while the guitar signal is audible, not on "idle" so to speak

I do not get the sound in stand alone mode from 11Rack via headphones.

I have checked (to the best of my ability that is) cables, other power sources etc. The sound is the same from different guitars, with different cables, and does not change if I move guitar positioning or cables or the like... It is present on all patches...
I have read through the threads regarding buzz and such, but they seem to be about constant sound even when not playing - I have turned off the noise gate on the various patches with no result - I have cycled through the true Z settings to no avail... Have unplugged, restarted and the usual...

Any suggestions as to what could be causing this and what to try to fix it? Again, It has not been this way forever, only recently, and without any changes (purposeful at any rate) on my part...

Thankful for any help-

Frank

[zedhed]

Is the Omni and 11R connected via s/pdif?

[BuddyReklam]

Hi!
Yes it is.