Thanks a lot for your quick answers. I tried with a booster but this does not solve the problem. And my guitar has strong pickups (gibson sg standard with 498T humbucker) which allow to reach the peak in the input signal.
I tried several configurations, in pre, post configurations as well as ‘normal’ and with the booster but each time it is the same: no noise at all when inserted in the effect loop, a superb sound, and a floor noise when in front of the amplifier (an ENGL ironball), in dsp mode or when activated (no noise in true bypass) and of course this is clearly more noticeable with the amp high gain channel. I definitely think it could come from an impedance issue between the h9 output and the input of the amplifier. Or maybe the power supply of the eventide (which has no ground pin contrary to the amplifier…) ?
