The Line 6 DT50 212 Guitar Combo Amp is an awesome piece of gear: it has "an amplification system that is able to configure and adapt its analog components and digital modeling in real time. This means that when you select a model, the DT50 Amp instantly reconfigures the tube power section to provide the optimal tone. The digital section monitors the tube power section and can adjust the DSP in real-time." However, controlling it is a beast... before Master Layout Designer François Desnoyer created this powerful MIDI Designer layout. It's been completely refactored for MDP2 to have only two pages and 72 controls, but don't underestimate this one: it packs a wallop. The version before MDP2 required 6 pages and 227 controls!
Thanks to PICKER and Bank/Prog Change controls, I drastically reduced number of pages and controls: NEW layout requires only 2 pages and a total of 72 controls (including "Forms"!!!!). Pre-MDP2 layout requires 6 pages and a total of 227 controls (no Form!!!)
With PICKER Control, I don't have to worry about space required on a page to fit all my selections. Now I can define all AMPS, CABS, Reverb, MIC and options presets in tiny PICKER Controls.
Need to say more 
?
Make sure to use MIDI channel 1 as DT50 will only listen to this MIDI channel.
Voicing controls on both AMP channels share the same MIDI CC (122). Channel "A" uses values 0 to 3 while Channel "B" uses values 4 to 7. Modifying Channel "A" or Channel "B" Voicing control will automatically change AMP channel from "A" to "B" (and vice-versa). This is not a bug in layout.
AMP/CAB MODE
- Mode 1 : Amps & Cabs
- Selecting AMPS AND CABS models automatically sets amp\cab tandem, Voicing, Negative Feedback loop, 12AX7 boost, Amp Class, Tube configuration, Feedback Capacitor and Phase Inversion B+ Voltage to default values sets by LINE6.
- Mode 2 : Amps Only.
- User selects amplifier model and then selects Cab, Voicing, Negative Feedback loop, Lamp boost level, Amp Class, Tube configuration, Feedback Capacitor and Phase Inversion B+ Voltage.
- For example, I like LINE 6 HIGHWAY 100 (modelized amp based on HIWATT 100), which is normally matched with 4X12 HIGHWAY cab by default, but I prefer sound of the same amp when matched with 4X12 XXL V-30 cab.
Use MASTER volume at least at 75% in NORMAL mode . Control channel overall volume with Channel Volume instead of MASTER. This way, you will hear the valve sound instead of modelling: this makes a HUGE difference.
But be careful: this amplifier is LOUD!!!!!!!!! 
From LINE6 Support Q&A
Q: How does the modeling of the DT50/DT25 contribute to the overall tone?
A: In the DT50/DT25's "normal mode", the modeling performs the function of the preamp: mating the digital preamp with the analog power amp so the whole system creates the sound of the amp modeled. This is different than our previous Spider Valve amps, where we modelled the entire amp model (pre-amp and power amp) and then fed that signal through the output tube power section.
In "low power mode" (pulling the master volume switch out on the DT50 or on the DT25 flipping the switch on the back panel), the digital modeling section will assume duties for the power amp section and the Master Volume has been scaled so that you can have the sound of a driven power amp at lower monitoring volume levels. If you turn the master volume knob all the way up in this mode, you will have Spider Valve-like tones behavior (where the pre and power amp software modeling signal is pushing the EL34 or EL84 tubes).
In both Normal and Low Power modes, cabinet modeling is applied to the output signal fed to the power tubes. When using a POD HD device connected via L6 Link, you must use the default cabinet model that is recalled on the POD HD 'pre' amp model when using the L6 Link connection with the DT amp to get the same type of sound as using the DT amplifier by itself with the same amp model.
Lastly, when using Low Volume Mode on the DT amp with a POD HD connected via L6 Link, the sound of a 'Pre' amp model selected on the POD preset will sound slightly different if an identical amp model is selected on the DT amplifier (on Channel B ). This is because when using the Low Volume Mode on the DT amp with L6 Link, Channel A on the DT amp with the POD modeling is still using the just the PRE amp model with the scaled Master Volume knob, whereas Channel B on the DT amp uses the preamp AND power amp modeling with the scaled Master Volume. The inclusion of the power modeling is what makes it sound differently.
DT50 HIDDEN CONTROLS.
Those are not the same as "hidden controls in MIDI Designer" but instead DT50 amplifier parameters tied to VOICING models.
- Some DT50 "hidden controls" can only be changed via MIDI as they are not visible on HD500 "on board" configuration window, HD500 Edit or DT50 amplifier itself.
- Hidden controls are tied to Voicing configuration and they can alter, in a some ways voicing models. More perceptible at higher volume (Reinhold Bogner amp designer is really a MASTER!)
- Note that any changes made on those "hidden controls" are saved in DT50 memory.
- If your DT50 does not respond as it should or if you want to go back to initial amplifier setup for “hidden controls”, just reset your amplifier (yes: there is a computer in this amp ...) by powering up the amp while holding down "Voicing Button" and holding up "Pentode/Triode Button". Process takes about 15 seconds to terminate.
I'm using "Glow" display as it is easier to view on stage 
