But $500 or so for each iPad... a traditional mixer would be vastly cheaper.
And iPads still don't multitask... You use one for the mixer, you can't use it for your lyric displays, or the Garage Band loop playback, or the MP3 player, or the synth app, etc..
I still don't have one of these. I think they need to get quite a bit more powerful before I do. That's a lot of dough to tie up in something that can't do two things at a time!
Plus, the DLM's only have TWO inputs. That's perhaps OK if you are a solo act with the barest minimum of needs. Saying they have a 'digital mixer' built in seems a bit of a stretch. A 2 channel digital mixer, maybe. But who has ever bought a TWO channel mixer?! Anyone joins you onstage, you are screwed!
A good idea, poorly executed, IMO.
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An arranger is just a tool. What matters is what you build with it..!