Hey there,
While I didn't notice clicking when turning on and fighting off the fx (unit isn't in front of me at the moment), I do notice that persistent ambient noise that doesn't change even if the volume does. This is while using headphones. I haven't checked or paid attention of the noise from recording the outputs, but I'll check.
The soft noise was noticeable to me after using a different pair of headphones. I try to ignore it, but the that sometimes makes it more prevalent to me. I just try to look at it as adding character to the sound. But you aren't alone on hearing it.
-Eric