I finished my D.I. Box, its based on the MXR M80 without the distortion and noise gate sections. I won't link the schematic but you can find it on line (google is your friend). It has EQ and Colour, which is a pseudo cabinet simulator. The Colour section only works if the EQ is engaged. With the EQ disengaged its a straight buffered unbalanced output and active XLR balanced output. The main reason I built this its because it can work with phantom power. With the EQ engaged you have a lot of flexible options with boost and cut for Volume, Bass, Mid and Treble.
This is my first designed PCB layout and althought it works pretty well I made some obvius errors, the most noticeable one is that the pots works backguard, so I made it look like a design decision in my decal design. Other important error in the layout its that I didn't check the footprint of some components, mainly the bipolar electrolytics. I also forgot to add VCC pads for the leds so I had to piggy back the connections in some pads on the solder side of the board, I can't take them from the DC jack because they should work with phantom power too.
I'm not really happy with the colour section, it sounds too muddy. As you can see in the next plot it is heavy scooped and a lot of treble attenuation, I'm not sure if schematic its correct in this section, I don't think the original unit works like this.
Tweaking the EQ knobs its possible to get a more useful frequency response. The next plot show the response with bass at min and mid and treble at max:
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