Preventing feedback loops with TotalMix submixes via Mackie Control

Hi all,

I recently bought a UCX II and am trying to setup some resampling routes.

I’m looking to use TotalMix FX with a Fireface UCX II as a hardware routing/resampling matrix for a number of synths, drum machines and samplers.

The idea is to have around 6–8 stereo hardware sources permanently connected to the UCX II/ADAT inputs, with several stereo hardware outputs acting as processing/sampling destinations — for example:

- Digitakt II input
- Elektron Tonverk input
- Torso S-4 input

I’d like to control this from a Mackie Control surface such as a Behringer X-Touch. My understanding is that in TotalMix Submix mode I can use the eight motorised faders as source/send levels, and the REC buttons to select the hardware output/submix being controlled. So I could select the S-4 output, raise the Syntakt fader to process it through the S-4, then select the Digitakt output and raise the S-4 return to sample the processed result into Digitakt.

The obvious concern is feedback loops. When the Digitakt input submix is selected, I never want the Digitakt output/input channel to be able to feed itself. Likewise S-4 → S-4 and Tonverk → Tonverk.

Is there a way in TotalMix to make particular source-to-output routes unavailable or locked at -∞, while leaving that source available in all the other submixes?

I know Channel Layout can hide channels from a MIDI Remote, but as far as I understand that applies to the remote globally rather than to an individual output submix. Ideally I’d want something like:

D2 submix: D2 source unavailable
S-4 submix: S-4 source unavailable
Tonverk submix: Tonverk source unavailable

D2 SEND selected
────────────────────
Syntakt      fader
D2           LOCKED / absent
Tonverk      fader
Hydra        fader
S-4          fader
...

S-4 SEND selected
────────────────────
Syntakt      fader
D2           fader
Tonverk      fader
Hydra        fader
S-4          LOCKED / absent

In other words, when I switch submixes on the X-Touch, the relevant “self-send” fader would either disappear/be skipped or simply be incapable of raising that route.

Is there a recommended way to achieve this in TotalMix/Mackie Control? Or, if hard locking individual matrix crosspoints isn’t possible, what would you recommend as the safest way of configuring this kind of hardware processing/resampling setup?

I don't want to buy the X-Touch unless I am sure it'll do what I need.  I'm trying to keep out of the computer and have a hands on way of routing.

Thanks.