Stumped:Headphone output is too revealing?

I recently picked up an SSL x-desk and running my guitar in through an amp pedal reveals a subtle but distracting buzzy sound when playing in the headphones. I don't hear this sound when playing the same config through the Apollo Twin Duo. Is it possible that the headphone output on the x-desk is accentuating or revealing this buzz in some way? Other sources sound great through the x-desk...it seems unique to these guitar pedals. I tried multiple pedals (Joyo American, Tech 21 Blonde, Joyo AC tone), switched guitars, played with levels, DI through a mic pre vs. line input, etc...sound still persists. If I route the sound through the x-desk but monitor the sound through the Apollo headphone jack, I don't hear the buzz. It seems to be a difference in the headphone outputs between the two units.



Anyone ever run into this? Any suggestions for a fix or workaround? Haven't been able to dial it out with EQ yet, but would love it if there was just something simple i'm missing.

Stumped:Headphone output is too revealing?