"I was thinking of doing a similar thing with just 2 preamps and a poweramp - how would one runa line to the desk from this setup though? It would have to be sent after the switch, but before the poweramp - A DI box stuck in there maybe??"
The system with the AKAI MB76 and other active MIDI programmable matrix line mixers might be (for one bass and two preamps) :
bass into line mixer Input channel 1, splits into various outputs to various preamps, say output 1 & 2 into preamp inputs
2 mono outputs from preamps, into line mixer input channel 2 & 3,
feeding output channel 3, which goes into your power amp
output channel 4 could be your line output to house PA, via a Di or line level
And if you want to you can patch effects in the chain either in series (for compression or distortion) or parallel ( for chorusing, reverbs and delays).
You could patch efx before the preamp or after as per your choice. And you could programme it so that your compression can kick in for parts of a tune, say when you slap...
Basically it is a programmable mixer/patch bay but the matrix configuration means that any output channel could be programmed to receive any configuration of input channels; and conversely any input channel can be patched to any configuration of output channels; albeit all with mix levels programmed as well.
What you do with this ability to patch/mix is up to your needs and imagination, and the matrix connections and MIDI switching make it more than a mixer.
for some reason I can't upload attachments, so I have tagged the pdf manual to a defunct standards band website I played in (band is no more but web ownership is still with me). Download the MB76 manual and see what you make of it. They turn up on ebay from time to time and are usually sub USD$100... I buy them when I see them and have a few.....The only downside is that the memory is not upgradeable and you have 'only' 32 programmes as opposed to standard 128 as is typical of later digital gear... but I'd say if you need more that 32 programmes from this unit you are not thinking enough about your music.....
download the manual at: www.thehepcats.com