External Power for Series Bass (Wireless Freedom)

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Next step (before you glue the tins together) is to create a flat surface for the 1/4 output jack.  You probably could use a narrow jack and actually put it on one side of the interior lip or the other, but I wanted mine centered for aesthetic reasons, which required cutting the lip away on the top.
 
This is a bit tricky as you want to cut close to the edge without cutting into the exposed outer surfaces.  
 

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Checking to make sure I had enough flat surface to work with . . .  
 

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Checking to make sure I didn't cut too far into the outside walls . . . not perfect, but any gaps should be covered by the jack and washer.
 

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Checking the alignment of the two cut-outs for the jack.  Make sure you file down and clean up the edges.
 

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Even with the filing, grinding and sanding, I was concerned about sharp edges and cutting myself or shorting the winding, so I put rubber edging around the interior lip.  I'm sure there are commercial products out there, but I bought quarter-inch vacuum hose from the local auto parts store, slit it lengthwise, cut it to length and used super glue to tack it in place.  Sturdy and much safer . . .  
 

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Sorry, skipped a step.  Before I glued the rubber tubing in place, I glued the two tins together using super glue.  Don't use too much, as you clamping two rigid, flat surfaces together.  I used the plain old thin super glue, not the thicker gel that's available now.
 
Once that's dried, you're ready to drill for the connections, starting with the 1/4 jack.

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Here's the result of drilling the hole for the 1/4 connector.  Okay, since most of it is covered up with the washer, but probably the most difficult part of the project because you are drilling in the center of two thin metal surfaces that aren't attached (remember you cut away the flange inside).
 
I used the rotary tool to start the hole, and a drill press to finish it, but it was still marginal in my opinion.  In retrospect, you could actually offset the hole, even if it were close to the center, and probably get better results.
 

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Here's the jack installed . . .
 

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And what it looks like from the outside.  Cleaned up pretty well.  I added an extra washer on the inside to provide a broader, flat, sturdy surface to tighten the jack into.
 

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The next step was installing the 5 conductor cable.  I used Canare mic cable, L-4E5C, which is the thin version of their star-quad cable - 4 conductors and excellent shielding.  I used a rubber grommet to hold it in place and protect it from the metal edges.
 

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I used a small bread board to put the circuit together and provide a connection point for the power and signal cabling.  Treble and bass signals go through a resistor combining network to produce a mono signal.  Batteries are wired in series and tapped in the center to produce + 18v and - 18v to ground.
 
I split the 5 conductor cable shielding 4 ways, discarded 2 of them, tied one to the power ground and the other to the ground/shield of the 1/4 connector.  Since the box is metal, I figure this effectively grounds/shields the whole device.  
 

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Here's the bottom of the breadboard.  Power on the right side, signal on the left side.  (Please, no commentary on my soldering skills - I don't do much anymore   )

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Here's the wiring completed and installed in the box.  I cut another breadboard about the same size as the first one and used a hot glue gun to glue it to the bottom of the circuit board.  Hot glue because you can disassemble it if needed, and it provides some stability and insulation between contacts.
 
I then hot glued that assembly to the shelf we created when we bent the cut out into place.  I put it beneath the 5 pin cable for spacing.  I also cut and laid out the breadboard so it would fit neatly on the shelf.
 
 

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Here's everything with the batteries installed.  I used narrow weather-stripping foam at the base of the box to keep the batteries snug against the shelf.  I also put two strips on the inside of each lid to hold them snug when the box is closed up.
 
 
 
 

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Here's the finished box, all closed up.  I used a Neutrik NC5FRX-B 5 pin right angle XLR connector.  I tried to find the connectors that Alembic uses with the flat backs just for consistency, but couldn't and found at least one indication that they're no longer available.  
 
The one I used is fine (it has a round back), but let me share one caution:  it comes disassembled, with parts of the shell and the pin insert, which clicks into place with a retaining spring when you insert it into the shell.  Do all of your soldering on the pin insert BEFORE you click it into place in the shell . . . because it ain't coming out once you do  
 
Don't ask me how I know this . . .