Here's a 12 channel mixer VST/AU Miksebord2https://audiostrom.com/?topic=mixer
(local download below so down the track it will still be available) Full Screen Pic KV Element
AUNetSend/Receive comes with mac.
In the tracks I put reastream-standalone.dll (using unique ID name for track) or AUNetSend and Sonalksis FreeG after it to mute the output to master but you can use anything with a gain or mute to prevent the output going to the master.
In the Master (Combo) track I load KV_Element VST/AU then in that I load reastream-standalone.dll (using the same unique ID name for track) or AUNetReceive
I then connect the audio output to Miksebord2x64 VST/AU
the stereo master connect to the audio output of KV Element
the send 1 output I connect to to Amplitube VST/AU
the audio output of Amplitube I connect the audio output of KV Element
You need to connect the KV Element audio input directly to the KV Element audio output or through a mixer channel if you want a master control.
This is just a simple example of what you can do.
(remove .mp4 to unzip)