Intro: How I Rack-mounted My Line 6 Pod Guitar Effects Processor
I bought one of the original Line 6 POD units when they first came out back in 1998. It sounded phenomenal back then and still sounds great today - the only problem was its shape - To put it plainly, it looks silly. More important, unless you've got ample desk space or use it alot on the road, there's no convenient place (at least in my cramped home studio area) to put it and keep it there. I like the convenience of rack-mounted units, but to get a new Pod XT Pro, it'd have to fork out about $700.00 - like many other people on this site - I decided to bust out the soldering iron and rackmount it myself.
Step 1: Let's See What's Inside...
Before doing anything harsh, I wanted to see what I was dealing with, so, time to open it up... once I stripped it down to the bare PCB and took a quick measurement, I was happy to see that the raw unit would indeed fit inside a 1U slot (i.e. under 1.75 inches) - with the largest component being the big capacitor.
Looking more at what needs to be done a bunch of components would have to be desoldered and wired up to the board to allow these to be accessible from the rack frame - these pieces being the four audio jacks (input, headphone output, and left / right outputs), the 2 rotary encoders (for amp model and effect selection), the 8 potentiometers (for various input), the power supply input, and the 2 MIDI jacks.
Since this will be inside the rack, I'd have to also create a break-out circuit for the display LEDs and for the buttons / switches... on to planning.
Step 2: Planning It All Out...
AutoCAD rules. By taking the dimensions of the Pod's PCB, the dimensions of the rack case I wanted to use (1U x 8" deep rackmount enclosure, Mouser part #546-RMCV19018BK1) and the rough dimensions of the various switches, knobs, buttons and jacks, I booted up AutoCAD and planned things out to see where things would best fit...
The resulting images are attached... they might be hard to see because of the detail of the lines and the small image sizes here, but trust me, the time and effort spent on this stage was well worth it. The final rack-mounted unit's dimensions and component placement went as planned.
Step 3: Time to Get De-soldering...
Before desoldering anything, I wanted to make sure I knew what went where... so I took a snapshot of the front and back of the loaded PCB and marked it up in Photoshop with all the appropriate connection points what what went where - unfortunately, I can't find these images to upload - but if you do decide to hack your own rack-mounted Pod - remember to do this! It'd be kind of silly to remove all the components only to realize that you don't know which was the positive and negative ends of the LEDs...
Anyhow - so, I busted out the old trusty Weller soldering iron, desoldering bulb, wick and suction-thingie and went to town... I removed all the jacks, potentiometers (which were all a pain in the butt), the rotary encoders (which were an even bigger pain in the butt to get out without breaking the leads), the 7-segment display, the LEDs, and the power jack. I didn't want to bother with the RJ-45 plug that they have to connect to a foot pedal, mainly because I knew I'd be controlling my unit via MIDI and my Behringer FCB-1010 footboard anyhow... why bother...
The image attached shows the desoldered board (three of the potentiometer wires have been attached too - I didn't stop to take any pictures while de-soldering, unfortunately)
Step 4: Creating a MIDI-thru
One of the things I never liked about the Pod was the fact that although it has a MIDI-IN and MIDI-OUT, there is no hardwired MIDI-thru port... I decided to fix this... On the existing PCB, the MIDI-IN port goes into a GN138 opto-isolator - what more perfect place to patch a MIDI-thru port onto then the output of the opto-isolator! One thing though is that to properly implement a MIDI-thru there should be a very light buffer delay - rather than using a dedicated buffer IC, I decided to get a cheap inverter (the 74HC14 - technically a Hex Schmitt-Trigger Inverter - like 22 cents each) and send the signal through two of the inverters (essentially negating the inversion) which causes a slight delay / buffer effect... then using a 220 ohm resistor to ensure to slightly limit the current on going out the line. By the way, you should be able to re-use this circuit on almost anything that you want to add a MIDI-thru port to - as long as you have a +5V connection, proper ground, and can get at a good, isolated signal from the MIDI-IN.
(BTW - this circuit works perfectly! I've not have any sync errors or speed delays patching through this MIDI-thru)
Step 5: Wiring Up the Jacks, Pots and Encoders...
This was fun - tedious, but straight-forward. For ever lead that was soldered onto the PCB, run a wire from that connection point to the lead on the component... I got in the habit of using black, red and green wires for my connections - the black going to the ground, the green being the center/hot, and red being the +5 line (when appropriate)...
To play it safe too, I flatted out the smaller capacitors on the board - and if you think that's a lot of wires now... wait a couple of steps...
Step 6: Preparing the Rack Case
Before things got too hectic, I decided to start working on the actual rack case. Since the case was made of decent aluminum, it was time to break out the Dremel and various drill bits and manual files...
The text for the labels was just printed out from a regular inkjet printer onto regular paper - I then smeared some clear-drying superglue across them to get them to stick to the painted metal. Not the most clean way (or professional way) of doing it, but it works, and none of the labels have come off to date.
The covering over where the LEDs and the 7-segment display is came from some old thin, black wire-mesh I had lying around.
For all the cuts / dimensions / spacing / etc. - this is really where the AutoCAD drawings came in handy -
Step 7: The LEDs and 7-Segment Display
The original Pod had used red LEDs and a red 7 segment display - for a bit of my own flavor, I used all green instead...
From the AutoCAD drawings, I had cut out a piece of breadboard to mount all the components on and the first thing I did was to solder the wires onto the new indicators. Each of these wires would eventually be soldered onto the appropriate place on the original PCB where I removed the original component...
When the back-side of the indicator breadboard was complete, I soldered on (directly to the PCB) wires for the push-button switch connections - after soldering each connection, I tacked down the wire with some hot glue to make sure it didn't shift.... (one note though - in the end, my connections for the push-buttons failed somewhere, so none of the push-buttons work - which is OK, because I control everything via MIDI anyhow... but if you want your buttons to work, use caution here!)
And then finally - the connections from the indicator breadboard was soldered onto the PCB... now that's starting to look like a mess of wires... At this point, I mounted the PCB in the rack frame to make it easier to work on...
Step 8: Mounting It All in the Rack Unit
Using a piece of 3/4" x 3/4" (1/16" thick) L-shaped aluminum, I fashioned a bracket for the rotary encoders and potentiometers to mount on. This in turn was secured to the frame. I also fashioned a small bracket to hold the indicator breadboard as well.
I then put the front faceplate on and attached the switches - and the the back with the jacks attached.
Then I compressed all the wires and put the top on...
Step 9: All Done! Fire It Up and Test It!
Finally - the moment of truth. I plugged in the power, flipped the switch, and lo and behold. It came to life.
After some tests with a guitar plugged in, I deemed it worthy enough to put into the rack. All knobs and MIDI functions work great - and with new audio jacks on it, the sound is quite clear. As I mentioned before, it's disappointing that the push buttons don't work, but that's OK because the MIDI functionality works 100% fine.
Step 10: Finale and Parts List
Just some final shots of the unit in the rack - much better!
Here's a list of parts used to get this done (purchased from both Mouser and Jameco)
103-1211-EV - Pushbutton Switch (x8)
540-SRB22A2FBBNN - Rocker Switch
589-7100-410 - ProtoBoard (10x4")
696-SSA-LXB10GW - 10 segment LED bargraph (green)
696-SSL-LX2573GD - 5mm x 2mm LED (green - x20)
604-SC56-21GWA - 7 segment LED (green x2)
565-7160 - 1/4" stereo jack (3 cond. x 5)
161-0005 - 5 pin DIN MIDI Jack (female x 3)
546-RMCV19018BK1 - Rackmount Enclosure - 1U x 8" deep
Toggle Switch (AIR): 75969CB
22 AWG Hookup Wire: (100', black): 36792 and/or (100' red): 36856 - solid
1/4 watt 220 ohm resistors (min. 100)- 690700
1x 74HC14 (hex inverter): 45364
Random hardware I had around...
PCB Standoffs (4x for PCB)
3/4" x 3/4" (1/16" thick) aluminum L bracket
Screws/Nuts for DIN Jacks (6x)
Screws/Nuts for Alum. LBracket/Plates