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M31_DIYM_iPdDck25_prtrt1

While I’m best known for chance-based “circuit bending,” I’ve been composing and playing deterministic music for much longer, and I’m always interested in experimental music technology. My hacked iPad 2, broken out into a Music Desk crammed with extreme audio apps, is my favorite new instrument.

On its own, the iPad sounds fine and its large touchscreen is a fantastic musician’s interface. But for studio use, the iPad is too lightweight; it needs added stability, better ergonomics, and a more professional wiring interface. That’s what this hack is all about.

Here’s how you can make a dockable Music Desk for your iPad by adding 1/4″ line inputs and outputs (Apple has the inputs reserved, but you’ll be ready if Apple opens them), video output, guitar/microphone input with level control, headphone output with level control, a power indicator LED, and a USB jack that will allow both stereo line input and MIDI I/O, via a MIDI-USB adapter.

Materials

  • ViewStand aluminum viewing stand for iPad — from Macally (macally.com), item #VIEWSTAND
  • PodBreakout Mini or PodBreakout Nano Style 1 — from Kineteka (kineteka.com), items #POD-DOCK-MINI or # POD-B-N-S1
  • Potentiometers, audio taper, panel mount: 50kΩ (1) and 1kΩ stereo (1)
  • RCA video jack, panel mount
  • Audio jacks, 1/4″, panel mount: mono (4 unswitched and 1 switched) and stereo (1)
  • USB jack, Mini-B type, panel mount I used Bulgin #PX0446.
  • LED, blue, 5mm
  • LED housing I used a vintage lens from my collection, but you can also use a ping pong ball (see Step 2).
  • Knobs, to fit 1/4″ shaft (2)
  • Cable clips for 5mm cable, adhesive (4)
  • Hookup wire, stranded, insulated copper, 22 gauge or so
  • Centronics parallel printer cable — These cheap, outmoded cables pile up at second-hand shops.
  • A/V cable, 1″ (3.5mm), 4-pole — These have 4 rings on the plug.
  • Heat-shrink tubing, 1/8″ diameter

Tools

  • Ruler
  • Pencil
  • Center punch and small hammer or mallet
  • Drill press (preferred) or hand drill
  • Drill bits: 1/8″, step bit
  • Hole saw, 3/4″ or a reamer to enlarge a smaller hole to 3/4″
  • Adjustable wrenches or nut drivers, small
  • Soldering pencil with chisel tip, 1mm–2mm
  • Solder
  • X-Acto knife
  • Wire strippers and cutters
  • Multimeter
  • Lighter or heat gun for the heat-shrink tubing
Related

Steps

Step #1: Cut the case.

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  • Following the cutting templates, measure and mark the hole positions on the Macally ViewStand. Use a center punch to indent all the marks, and then pilot-drill them with a 1/8" bit.
  • Next, use a step bit (or regular twist bits of the correct sizes), to carefully redrill all holes up to the correct diameter. For the 3/4" hole to fit the panel-mount USB jack, you can use a hole saw with a metal-cutting blade or use a reamer to expand the largest hole you can drill.

Step #2: Mount the components.

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iPad Music Desk
  • Place all the jacks and pots in their proper holes and hand-tighten their mounting hardware. The stereo pot is for the headphones. Using nut drivers or small adjustable wrenches, tighten all the hex nuts.
  • The ViewStand has a large hole in the middle for a plastic stabilizer that prevents it from tipping forward. This is where you install the LED. I enclosed mine in a vintage Cold War lamp housing that I adapted, but you could also drill a ping-pong ball, wire the LED inside the ball, and glue it behind the opening. Be creative and make the dock your own!
  • Want to save battery power? Add a switch for the LED, or find something else to do with that big round hole. A vintage analog mini VU meter would be cool. So would a nixie tube or magic eye radio tube winking with the music. With the right amp and limiters, both options are possible.

Step #3: Wire the components.

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  • Follow the schematic diagram to wire the components, soldering the connections with hookup wire. Start with all the grounding wires; I used green for these. Then solder the potentiometers (yellow wires): one wire between the guitar pot and “hot” side of the guitar jack; 2 wires between the “hot” sides of the line output jacks (note R/L) and the headphone pot; and 2 more from this pot into the stereo headphone jack (cable clips shown are added later).
  • Remember that LEDs are polarized. The cathode (the shorter leg, on the side with the flat face) should connect to ground.

Step #4: Make the docking cable.

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iPad Music Desk
  • It’s time to create the 30-pin docking patch cable. Referring to the photo, cut a 22" section from your printer cable. Strip 1" of insulation from one end and 8" from the other (lightly score the outer plastic with a sharp knife and then pull it apart). Leave the inner foil shield intact.
  • Trim the foil shielding away from the 1" wires. From the other end, where the outer insulation stops, pull the bare ground wire and 4 other wires through the foil. Pull another 7 wires through the foil 3" further down the cable. Loop the remaining foiled wires and reserve them for later expansions.
  • At the 1" end, noting color codes, cut away all the wires that you did not pull through the foil at the other end (those reserved and still wrapped in foil). This will leave 12 wires at the 1" end including the bare ground wire.
  • NOTE: Be careful when sorting colors; lookalike colors will have a white stripe, or something else to differentiate them, though the difference is sometimes easy to overlook.

Step #5:

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iPad Music Desk
  • The next step is to solder the 12 wires to the Kineteka PodBreakout Mini, a finely crafted experimenter’s board with soldering holes connected to a 30-pin docking plug. You’ll connect all but 3 of these wires to soldering holes, which makes this an easy job, so long as you trim the wires to the approximate lengths needed. The remaining 3 wires connect to pins on the PCB, which is also easy with a fine-point soldering pencil if you twist and tin the wires prior to soldering. (If you're using the new PodBreakout Nano Style 1, follow the schematic but solder the 3 “pin” wires into their respective pads.)
  • Follow the diagram to assign wires to functions and contacts on the PodBreakout. The color-coding scheme is up to you, but be sure to chart it as you go along. For example: Pin 3, Right Out = red wire; Pin 4, Left Out = orange wire with white stripe; etc.

Step #6:

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  • Holding the 1" end of the cable against the PodBreakout with the insulation inside the collar, snip, strip, and tin the 12 wires to approximate length according to destination. Give each one an extra 1/8" for soldering. Leave 3 of the insulated wires a little longer; one must reach to the backside and 2 will run to pins a little past the soldering holes on the front.
  • Starting at one end, connect the 9 shorter wires to their holes by soldering their tips sticking out the backside of the board. The bare ground wire goes to hole 1, and the 4 other wires that you first tugged through the foil at the other end of the cable are for the Line In/Out jacks and go to holes 3, 4, 5, and 6.
  • Solder the 3 longer wires to pins 11 and 15 on the front, and pin 18 on the back, running the wire through empty hole 21. To solder to the pins, hold the tinned end of your wire along and on top of the pin. Lightly place the soldering tip on top, and remove it as soon as you see the solder of both wire and pin flow together. Hold the wire until the solder hardens.
  • Double-check the wiring. Be sure you’ve charted all color-to-plug connections. Align the plug hardware and snap its case together.
  • NOTE: Tinning is an ultra-thin application of solder, simple but very important. Get the target hot, and then apply a tiny bit of solder until it coats the metal or is absorbed into a stranded wire.

Step #7: Make the 1/8 inch patch cable.

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  • We now breeze on to hacking the 4-pole A/V cable. Cut the phono plugs off about 14" from the 1/8" jack and strip the ends.
  • Checking continuity with a multimeter, ascertain which rings of the plug terminate in which wires (ring 3, counting from the tip, is ground and will connect to the shields of all 3 cables).
  • Peel the cable back to 9" and cut to that length the wire that connects to ring 4 of the jack, the guitar input.

Step #8: Connect the cables.

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  • Attach the adhesive cable guides as shown in the first photo, and run the breakout cable through them. Solder the color-coded wires to their destinations, referring to the second and third photos. Trim, strip, and tin as you go, and insulate the USB connections with heat-shrink tubing.
  • Also run and connect the 1/8" A/V cable. Use a X-Acto knife to trim the plug down if it hits the edge of the desk; mine did.
  • Check your wiring and install the 2 knobs on the pots. Set your iPad in place, plug the PodBreakout into the docking port and the A/V plug into the headphone jack. Your iPad Music Desk is complete!

Step #9: Studio Ready

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iPad Music Desk
  • Using the iPad Music Desk is a pleasure, since it now not only sounds good, it also feels like a serious, professional piece of gear.
  • Line outputs allow patching signals to amps, mixers, and so on.
  • The USB port allows connection to USB-compliant I/O devices (line input, MIDI, preamps, etc.), however, Apple recommends that you only attach cameras to the iPad via USB. It’s up to you to determine whether your USB device will work. As with any hack, you’re on your own, Mr. Tesla.
  • The Guitar/Mic input provides only adjustable attenuation, so as not to add unexpected components to the signal path. This lets the iPad Music Desk work with devices like the AmpliTube iRig, for example, which plugs into an iPhone or iPad’s headphone jack to turn it into a broadly configurable guitar effects pedal. (If you use one, turn your Desk volume all the way up so that iRig “sees” the expected signal path.)
  • Finally, the composite video jack provides Apple Slideshow output.
  • I really dig running experimental apps like Droneo, Curtis, or Reactable into a big sound system, with fingertips on the graphics of the iPad’s responsive screen, the whole thing broken out of iPad frailty and now feeling Moog-solid. It makes me think back to the Moog’s cool ribbon controller, and the Martenot’s weird finger-ring playing system. Wow, music controllers have come a long, long way!

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