I am trying to run my H9 in pre/post but the noise level is unbearable. When I only hook up one side of it the noise level drops to where you would expect it to be. But every time I hook up both the pre and post side the noise level jumps to an unreasonable level.

Simplifying the chain so it is only Gtr > H9 > One Stompbox > H9 > Amp. Nothing has made a difference. What else can I try?

If you

1. set your H9 to Pre/Post mode

2. connect your Guitar to H9's Input 1

3. connect H9's Output 1 to Input 2

4. connect H9's Output 2 to your amp

Does it make any difference when you change the mode of your current preset from PRE to POST?