Just found this...
"
To be specific, there exists a "Mix" parameter for each B3 amplifier sim that should be set based on your connected equipment, usage intent, and ultimately, the tone that is desired. The "Mix" in this case is the level of the preamp simulation vs. the cabinet-effected simulation. The lukewarm default for all amp sims on the B3 is always an ineffective 50%. Yes, you will hear something using that value, but it most likely is not exactly what you want to hear.
To keep things simple for now, I will only focus on this "Mix" parameter for the amp sims and not any other patch-level (i.e. TOTAL menu) or device-level (i.e. GLOBAL menu) parameters.
For my "power amp and real bass cabinets" situation (see my previous posts) I have found the best results are achieved using 100% of the preamp sim and 0% of the cabinet sim. This equates to a "Mix" parameter value of 0 and NOT the default value of 50. IMHO this difference has a very measurable impact on the resulting tone and is worthy of your attention and experimentation.
In situations where you are feeding a mixer, recorder or projecting through a full-range monitor speaker (QSC K, Mackie SRM, etc.) I have found the best results are achieved using 0% of the preamp sim and 100% of the cabinet sim. This equates to a "Mix" parameter value of 100 and NOT the default value of 50. Try it for yourself and it is likely the B3 will then become your new best friend.
"
Interesting. Only thing not covered is whether the MIX function applies to all outputs or either DI / Amp outputs..
Further reading would indicate that Cab Sim is applied to both, or not. Seems odd to me that you cant send a Cab Sim to DI and no Cab Sim to your amp...
I'm fairly sure Line6 have always had this option. DI has the cab sim applied, but the standard output doesn't..