I need help designing a portable powered audio mixer.

 As the title states I need some help in designing a mixer that I am going to use for home recording and on stage to EQ my drum kit.

I feel I will be able to actually build the thing and have a rough idea of a schematic but my depth of knowledge ends when it comes to powering the mixer and exactly what parts I will need in terms of resistors, pots and power supply.

The unit will act as a pre-amp, mixer and EQ.

I want a total of 12 inputs and 5 outputs. 
This breaks done as...
1 headphone out
3 Grouped outputs 
1 Main output

Each channel will have 1 bass, 1 treble, 1 volume and a selector to chose whether the signal is routed to the grouped output or the all-out output.

I could really do with some help designing this.
Thanks in advance!
el Ginjo,,


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