Sure, that’s one place where dither can be needed.   

Dither is needed to avoid truncation distortion.  TotalMix will truncate outputs, There must be a dither option for when a fader is not at unity.  Is there not ?  Can’t believe that would be the case.

I agree, any digital mixer should have that built in.  I have also learned to never guess with audio, you’ll be surprised quite often.  I am getting the impression this isn’t an option for the user, does anyone know with certainty that TotalMix does dither it’s outputs to avoid truncation distortion?

Sorry, I can't answer that question. But usually you can expect from RME products, that everything is being
designed to have very good quality.

As you know the NAMM show is running in the USA right now.

It's best to wait a little longer until someone from RME comes up with an answer before jumping to conclusions.

Indeed it is. 20 years after this

https://archiv.rme-audio.de/old/english … tmhard.htm

one should expect some knowledge when Dither makes sense and when not.

There are two points: truncation at 24 bits is of zero consequence unless you discuss theoretical limts that nobody will ever experience in real-world applications. The sources and the destinations are all much worse than 24 bit resolution, and noise is and works like dither. That's why that article included a simple measurement to show what happens when you lower the signal. And the article also states that 'the other 5 bit are used for the LSB to decrease rounding errors which has an effect similar to low level dither.

Note that TotalMix is a monitoring / mixer tool. It is not intended to work within DAWs at floating point resolution.

You are 100% wrong, really. This discussion pops up everywhere one time or another. Last one I followed was very lengthy on the Nuendo forum. No nuendo does not dither also on its internal mixer.
If you still believe you are right try the following. Take a nice clean sine wave, one that easy to hear when it gets distortion. Lower the level step by step and up the monitors or headphones. If there comes a point that the sine starts sounding like a square, you are right and I will eat crow. If silence or noise wins, you will say sorry, right? Thing is I tried this, with a  sampler with 16 bit outputs and no dither, which was because I did not believe dither noise worked. But it did. Lowered the level till sounded like square, played a low level noise sample et voila sine was back. You can not repeat this yet with 24 bit converters, no matter how good. If we would ever get converters with a144db noise floor, then it would at least be a theoretical problem. Still If I remember correctly we will never get that silent because of electron noise in electronics at current levels.

The simple reason is bit tranparency at 0 dB gain. Apart from that there is no need to continue this discussion. You are not forced to use TM FX if you think it decreases sound quality. Set everything to unity and use your DAW's mixer instead.

Well, at least you created a truly unique sentence...

Zero results in several search engines, except of course for this thread. Makes you wonder.

...so I typed the exact sentence into google and was hit with a ton of relevant results.  Indeed, Makes me wonder

Dithering any outputs which has a fader other than unity is not useless.  This would avoid truncation distortion. 

This is an issue with total mix.  It isn’t if you don’t move the faders, but then why include the faders in the first place if the argument is that total mix is only for routing.  I want to be able to use total mix and it’s faders without truncation distortion.  I was surprised to find out that total mix just truncates.  That’s all.  I expected truncation distortion to be avoidable in total mix and it isnt unless you leave the faders alone. 

Not hard to understand.

so much theory in this post, totalmix is the last thing you need to worry bro in music production or even mastering

Again, disagree. It is very unsubtle and turns a sine into a square really. But only when level drops to -144db. That is the point you are missing. Except for a computer generated sine at -144db there is no audio at that level.
But . and I am still trying to help here and it would be nice if you acknowledge this, If you have an experience that dither makes the audio nicer, that is a known psychoacoustic effect. That is why the analogue button on waves plugins add noise (as is in the emulated hardware) Noise has the strange effect of adding something nice to a sound. In reality nothing is ever noise free. The whole, same, discussion on the nuendo forum, where someone claimed to hear improved audio with dithering all non 0db channels, in the end proved to be the psychoacoustic effect of the used dither/added noise. You can even use noise shaped dither at 16 bits in a 24 bit environment ass an effect, just as adding needle noise to a hip hop track.
Cheers!

At the low levels the distortion is occurring, it is very subtle.  If you choose not to care, that is your choice.  There is always the choice. Noise or distortion.  You simply choose distortion because you feel it is too subtle to be bothered with.