Thanks for the response. I've checked all connections. Power supply is good.
When the H9 is used alone (not in series with any other pedals) it's dead quiet.
Similarly, when the other three pedals are used without the H9 in the signal chain, they are also dead quiet.
When the H9 is placed in the signal chain (regardless of the cable used…George L, Monster, Lava, etc…) there is a low humming which is noticeable even with everything in bypass mode.
Tried this with an entirely different pedalboard and had the same results. It seems like anything placed before the H9 in the signal chain causes this humming.
This makes no sense to me.
