Using mixer as 4 way preamp

The Ultradrive has crossover and EQ functionality but it's not really designed to be tweaked with all the time it's more designed to be setup and left alone, you can change things fairly easily via the remote PC application but it's clunky to put it mildly.

That soundcraft mixer has some EQ on each channel but the controls don't cut sound completely at it's fully counter clockwise position they just boost or cut 15dB. 

So you could route the DJ mixer through the DCX to separate the signal into 4 bands with the crossover functions, then bring that through 4 separate inputs of the Soundcraft mixer but each input will already be bandwidth limited,  so for example the mid and high EQ and the sub channel won't have any effect, the low and high EQ won't do anything on the mid channel, etc,  so the only thing you can really do it raise or lower the level of each band and cut it completely if you want, or add an effect. And yeah the output of the mixer would then be a mono mix of everything that would need to be split via another crossover, so it's convoluted and still not very effective.

Another way to use the gear would be to go from the DJ mixer to the Soundcraft first with just the stereo signal, you can add EFX when you like and play with the EQ some, then it goes to the DCX where the signal is split up and sent to the respective amplifiers for each speaker section. You don't have the same level of control but it's a relatively straight forward rig to wire up. 

Neither one of these scenarios produces exactly the same results as a reggae preamp but it is what it is. Do you have the Soundcraft mixer already? Modern DJ mixers have more of the functionality you are looking for with built-in effects and full cut EQs.

and the musical phase is in a total mess... even big noise introduced in all music chain.

i reply to this because ive seen one famous sound doing like this, and its the most espensive crap ive ever seen.

please make it simpler, and thinking that a reggae preamp is a real save of money for playing how u want...and maybe you can put the summed exit in a proper dsp and drive yuor system properly