H9 MIDI Question

I have read the H9 manual on MIDI (pages 26 and 46) and it does say that the H9 will automatically look to the usb port  when it is connected.  

I think the answer is "no" but my question is this:  If a usb host/controller is connected to a first H9 usb port to send midi output level messages to that first H9, can the DIN port of that first H9 still be used to send preset increment midi message from that first H9 to a second H9? 

I'm looking at simple (Midi Baby?) ways to use MIDI to control/change the output level of an H9 since there is no expression pedal control over the output fader.   I like the Idea of using the usb port but I think if I do that, I can no longer link two H9's via DIN.

The answer is NO. If USB port is connected, that will precedes DIN and H9 will ignore DIN.

You can connect your MIDI controller to your first H9's DIN input, and connect your 1st H9's MIDI OUT to 2nd H9's MIDI IN. This should work for what you want.

Be careful, MIDI Baby does not work with H9 using the USB port. I know this because I own a MIDI Baby 3. I confirmed with their support. Also, Disaster Area has a list of all compatible devices on their page. Our new dot9 series pedals, on the other hand, do work with USB-host controllers.

When an H9 is connected to a MIDI host with a USB cable, does that H9 both send and receive MIDI commands through that one USB cable?

Yes. But the host should be something like a PC/Mac, but not a MIDI controller.

I ask b/c it appears that the Disaster Area Midi Baby (3) has usb and DIN ports that are assignable for MIDI THRU.  So it seems I could achieve the goal described above as follows:

Connect a MIDI Baby to a first H9 with a USB cable.  Set the MIDI Baby DIN port as MIDI THRU. And, connect the MIDI Baby to a second H9 using the DIN port. 

That way the MIDI Baby could send MIDI commands to both H9's and MIDI commands from the first H9 would still make it to the second H9 (it would be irrelevant that one H9 is communicating through USB and the other is communication through DIN). Is that correct?

No. Because once you connect USB port on your 1st H9, it disables it DIN input and output. Why don't you just connect MIDI BABY to your 1st H9 via DIN, and your 1st H9 to your 2nd H9 via DIN as well? Set your 1st H9's MIDI setting to thru, then you can use your MIDI BABY to control your 2 H9s.