Have you tried relay bypass your H9?
I have no issue in bypass mode. All 3 modes have no hum noise when activated.
However in my usecase i need to have the H9 active and only engage via the send knobs for each channel i want to run my effect on my mixer which in turn send that channel’s signal to the pedal which then returns it to the return channel of the mixer. This is the standard way most djs utilize pedals for effects in their live acts.
So I need to have the H9 active all the time. But when no signal is passing, since my send knobs are off, there is this hum noise coming from the return channel.