RME manufacturers a wide range of high-end audio interfaces popular amongst professional musicians and audio engineers. Totalmix is an incredibly powerful and flexible software application used to mix and route audio on RME's devices. It all works great with JackTrip! I'll step you through a simple configuration while highlighting some common pitfalls.
The first thing to know is that JackTrip currently requires you to have all your sound available from one (mono) or two (stereo) "input" channels. If you want to use more than just two contiguous hardware channels (i.e. 1/2 or 3/4), you will need to use Totalmix's loopback feature to create a custom mix for JackTrip. Here is a great YouTube video that provides an overview of how loopback works.
For this example, I'm going to enable loopback on RME's analog hardware output channels 1 & 2, and configure JackTrip to get your sound from these first two channels. We'll configure JackTrip to send everyone else's sound to RME's software channels 3 & 4.
I'm using a Babyface Pro FS, but this should work the same for other RME interfaces. You can use different channel pairs. Just be aware that OSX users need JackTrip 2.2.3 or later when using channel numbers higher than 4.
In Totalmix, start out by setting the volume for all of your hardware (top) and software (middle) input channels to zero, for both your headphones and analog 1/2 hardware output channels. Failing to do this may cause feedback loops or echo audio back to all participants in your studio!
Next, select your headphones output (bottom) channels and turn up the volume on the software (middle) 3/4 channels. These are the channels that we have configured JackTrip to send everyone else's sound into, and it may be helpful to rename them to "JackTrip." Note that you can alternatively use software channels 1/2, but I will be using Ableton for those.
Click on the "Play Test Tone" button in JackTrip. You should see the volume meters for JackTrip (software input 3/4) light up in Totalmix, and hear the tone clearly in your headphones. Adjust your volume levels as necessary.
Note that all of your other hardware (top) and software (middle) input channels have their volume levels set to zero. You may choose to turn up levels specific for instruments that you want to monitor in your headphones using Totalmix; OR you can use the "Monitor" volume slider in JackTrip to do that. We recommend that you either leave these set to zero in Totalmix, OR leave your Monitor volume slider in JackTrip set to zero; otherwise, you'll have two different monitors running which will make adjusting levels very confusing for you!
Next, select your output (bottom) channels 1/2 in Totalmix (likely your "Main"), and enable loopback. Double-check that all of the hardware (top) and software (middle) input channel sliders are set to zero. Then, turn up the levels only for the instruments that you want to send to everyone else using JackTrip.
In my example, I also have the volume turned up on my first two software (middle) input channels, which allows me to route my audio from Ableton to JackTrip. You can use the same channels for any other apps, or other software channels if you prefer. Just don't reuse the same channel that JackTrip is using (3/4)! Also, the software (middle) input channels for JackTrip MUST have the levels set to zero; otherwise you will generate echo and possibly a feedback loop!
Speaking into your mic, playing your instruments, or playing audio from other software (like Ableton) should now make your JackTrip "input" volume slider light up.
With this setup, you should be able to have a great experience jamming on JackTrip with your RME hardware. As always, please let us know if you run into any problems or have questions. We are here to help!