Cheap Replacement XPS Power Supply (A/B Box) for the Original Variax Guitars

The prices of Line 6 XPS boxes are crazy, if you can find one, and running a Variax on batteries is a pain so I decided to make a replacement XPS box. It will only work with the original Variax guitars - 300, 500, 600 and 700. It doesn't have the A/B DI capability of the original Line 6 box, it's just a "phantom" power supply.

It was designed to be cheap and simple. The XL4016E1 power board only costs £6-£8 and it filters out noise so you can use pretty much any cheap DC power supply ; 9-35v 1500mA (1000 mA might work, I haven't tested one). No need to buy an expensive guitar foot pedal supply. Any sturdy box of the right size will do. I've included a link to my 3D print design.

Supplies

Tools - wire snips, soldering iron, multi-meter. slot screwdriver. Drill and bits if not using printed box.

Parts -

3D printed box, project enclosure box or similar.

XL4016E1 DC 4-40V to DC 1.25-36V 8A Buck Converter board

1/4" mono jack socket, 1/4" stereo jack socket (or two stereo)

Any cheap DC power supply 9-35V. 9-15V 1500mA is preferred.

DC power supply socket to match power supply.

assorted coloured wire

Stereo (TRS) 1/4" instrument lead/cord/cable.

Optional - 4 pickguard screws for the 3D printed box

Step 1: The Box

3D print the box (https://www.tinkercad.com/things/5zqgYFxLBRM-variax-xps-box). 100% fill and enable supports. These are only needed for the DC input socket which is an 11mm barrel type. Change the design if you are using some other type of socket.

Alternatively, drill out a box (internal dimensions of at least 95mm W x 65mm D x 40mm H) for the two 1/4" sockets and your DC power supply socket. Drill a hole or two low down on the side nearest to where the power board heatsinks will be and one or two above them for ventilation. This is probably only needed for heat dissipation with a DC supply over 12 volts but it's a good idea to drill them anyway. A cool power supply lasts longer.

Step 2: Wire Power Board and Sockets

Wire up the sockets as per diagram. Screw the relevant wires into the terminals. Attach the supplied feet/standoffs to the power board. Don't fit the pot knob. Before glueing, plug in your DC power supply and adjust the potentiometer until you get 7.2V DC across the 1/4" socket side output screw terminals.

Step 3: Installation

Just apply glue to the power board feet and stick down, then screw the 1/4" sockets in place. Plug in the power supply and check again that the output is 7.2 volts. That's it. The Variax plugs into the stereo socket with a stereo lead and the mono socket goes to your amp/fx.

If you want to double check it is wired correctly plug in both leads and test the jack plugs with your meter. There should only be a voltage between the ring (+7.2v) of the the stereo jack and the earth/sleeve of either of the two jacks.

Step 4: Usage

It's advisable to make the guitar and amp connections before plugging in the power supply but I have forgotten to do this a couple of times and nothing bad happened. Like the official Line 6 XPS, definitely DO NOT use this when the guitar has a VDI digital interface cable plugged in.

[The design of the 3D printed box was changed slightly from the one pictured. Just a couple of refinements].