Only the H9 with the provided wall-wart and the amp are plugged into an isolated outlet. No other pedals plugged in similarly produce the same problem.
No audio interface or anything else. The pedal also does a thumping noise and crackles. All cables are good and the problem resolves with any other equipment other than the H9, so I’m sure it’s the source of the issue. The problem persists whether I plug it into a different outlet, a power conditioner, or the eventide/cioks pedal power for pedalboards.
It gets worse when the bluetooth is connected, but still bad without anything connected that way. I typically use it pre/post but the problem persists if just straight in. I also usually run it as dsp bypass, but the noises are there when engaged in true bypass as well.
I would say not the H9, for one, because I think you can see the signal light flashing on/off with the noise. That indicates to me something is getting in the signal path somewhere before the H9. Is this H9 wired PRE/POST, or stereo? What happens if you use true bypass?
I would go through the connections first and eliminate any obvious sources of ground loops (non-isolated power supplies, grounds, etc.) or noise and start process of elimination between the H9 and front of the amp.
Hard to say but sounds like a power supply, interference or grounding issue to me.