Thank you so much.

What are you trying to do?  Use FS1 within a patch to change amp channels?

- you are correct.

It looks like the Midi Solutions Relay (hereafter 'The Relay') can be programmed to respond to either Midi PC Patch change or Midi CC Controller change  messages (amongst others).  The HD500 can send either.   The HD500 automatically sends out a PC message whenever you select a patch corresponding to the patch number (0-63).   If you do not want this behaviour, and always want to change channel using an assigned FS1, then can I suggest that you use a CC Message as this will make things clearer to work with.

You program the  the Relay to respond to the CC (or other message) using the software here --> http://www.midisolutions.com/ptprocessors.htm .   This software works on 32-bit Windows only.  The software sends a 'SysEx' message to the Relay that sets what messages the Relay will respond to.  This is a one off operation and you will need to work this out yourself (I am running 64-bit Windows ).  Make sure that you set the Midi Channel on the Relay to 1.  Make a note of the CC Message number and value that you have configured the relay to work with.

Now, run your Midi cable from the HD500 Midi Out to the Relay Midi In.  Go to your preset and configure FS1 so that it sends out the Midi CC Message number and value when you press the relay button.  Make sure it sends the message on Midi Channel 1.  You may need to use a Midi CC Toggle message to toggle back and forward between the channels on the amp.  I cannot tell.

- i knows it can be programmed. but i don't know it has to program before use it? i try to contact to Midi solutions support team. but havenot any response from them and that software required only window 32bit, which i have not. - -!

So.from your suggested, i thinks it need to program before use it.

Thank you so much again.