@GroovinDJ: I designed the VMS4 firmware and did not put compression or limiting on the audio circuitry. Typically the EQ and Master knobs will be somewhere near the middle and the faders will be about 2/3 from the top to produce the best sound quality. There will be some variation depending on how strong or weak the original audio sources are.
If you run all 3 EQs up +6dB what that means is the overall sound would get boosted by +6dB not by +18dB. So depending on the music this change may not be so visible in the VU meters. But once you start reaching the output limits you will hear distortion.
The meter readings will be as follows:
Master (not booth) if no cues are pressed
Pre-master cue if one or more cues are pressed.
So if you are using the booth output watch out with the adjustments because you may be reading master but listening to booth. The master and booth gain are identical so if you are using both, ideally you should set up the system amps so both have the same VMS4 settings.
I'm not sure where the crosstalk is coming from frankly. When I test my unit with the entire VMS4 cranked to the max and cueing a signal, I get nothing on the master. Same with Channel 2 set to zero. The only thing I can think of is if you are not using MIDILOG2 or MIDILOG3 analog inputs, set them for line level. If they are set to phono level, crosstalk noise of -90dB gets boosted by the phono pre-amp to perhaps -60dB or so which could become slightly audible through the channel.