Integrating this Bluetooth interface into your workflow will be a real challenge with the equipment you have. You should really consider to use vMix Call for that. There's only one way to make this work without getting a loop somewhere in the chain. But I will come back to this later. Let's focus on the other stuff.
I prefer to use the Master audio bus just for recording and streaming. For other routings including audio hardware outputs I use bus A and B.
To get the audio output from your DJ software into vMix you need a virtual audio cable. Download this package:
http://vbaudio.jcedevelo...BCABLE_Driver_Pack43.zipUnzip it to a folder and open the VBCABLE_Setup_x64.exe with admin rights.
Reboot, open the DJ software and go to Preferences --> Sound Hardware --> Output and set the Master to 'CABLE Input (VB-Audio Virtual Cable)'
In vMix set the audio output for the Master to none. This will be the bus for streaming and recording and doesn't need to be routed to hardware.
Set the audio output for Headphones to none. You're using the headphones connected to the Mackie.
Set the audio output for Bus A to the Mackie (Bus B = none).
Add an audio input for your Mackie. Be sure that this is
not routed to bus A.
Any other vMix input with audio (videos...) should be routed to M and A.
Add an audio input and choose 'CABLE Output (VB-Audio Virtual Cable)'. Route it to M and A. This is the audio from the DJ software.
Be sure that the "USB Thru" button on the Mackie is
not pressed/engaged.
Set the PC audio volume with the "USB Input Level" knob on the Mackie.
Take care what inputs you want to be always active or auto mixed:
http://www.vmix.com/help19/Mixer.htmlNow it should all work without having loops and echo.
If you really want to use your Bluetooth interface:
Go to vMix settings --> Audio Outputs and set Bus B to your Mainboard audio.
Route all inputs to send to your caller to Bus B. Do
not route the Mackie input to B.
Connect your Mainboard audio output to a stereo line in on the Mackie e.g. channel 5/6.
Set the gain correctly: Page 3 of the Mackie manual.
Mute this channel, leave the fader down, just set the 'Mon' knob to 'U'.
Set the 'Mon' knob on channel 1 (Microphone) to 'U'. Do
not turn the 'Mon' knob on channel 3 (Blue Driver), leave it at 0.
Change the cable connected to 'FX Send' to 'Mon Send'. Control the audio level to your caller with the 'Mon' fader.
Have fun...