A good client of mine bought a couple of Mikrophonie kits as he wanted me to not only build them but also replace the 3.5mm mic input socket with a 1/4 inch jack AND replace the 3.5mm output socket with a banana socket!
I thought I'd post up how I did it in case anyone else wants to do the same. Caveat: do so at your own risk!
- a hacksaw (and a hand file, probably)
- some drill bits (to open out the two holes in the front panel)
- 1N418 diode (or similar)
- 1 x banana socket
- 1 x 1/4 inch jack (switch type)
- a bit of small-guage multi-core wire
- a Mikrophonie!
- soldering iron, wire cutters, solder etc.
Got all that? OK, here we go!
If you're at the not-yet-built-the-Mikrophone, it's probably best to do this modification at that stage. If it's already built you'd be strongly advised to desolder the piezo as it will make the dirty work much easier. You'll also notice I've not soldered the 3.5mm sockets. Again, it will make things easier if you haven't but not impossible and you won't need to desolder them. You'll see why in a minute!
As you can see, there's a little problem: the bottom of the PCB is in the way. Never mind, we're going to just saw it off! Yes, you heard right!
Hold the PCB in a small vice and carefully hacksaw the bottom bit of the PCB off at the red dotted line. It doesn't have to be totally accurate as we will probably need to file it down later anyway. Just don't get too close to the resistor above the line - we need that intact!
The other dirty job we need to do is make the MIC IN and OUT holes larger to accommodate the 1/4 inch jack and the banana socket. Go steady and, especially the MIC IN hole, use gradually larger drill bits until you get to the required size. I always drill to just under the required diameter and finish off the hole with a hand reamer as it's the best way to get a properly round hole with a good finish. If you're doing this don't forget to do the last few MM from the opposite side (with the hand reamer) or you'll have a slightly tapered hole. Probably doesn't matter in this context but it's good to do things right!
So when you're done you'll end up with something like this! You can throw the small bit of PCB away, we won't be needing that any more!
Mount the banana socket and the 1/4 jack and tighten up. Next mount the PCB back onto the front panel (using the pot as before). At this stage it may not fit as there is barely enough room between the bottom cut edge of the PCB and the 1/4 jack body. If it doesn't fit, file the cut edge until it does. Be careful not to go too far with the file as you may damage the resistor and/or the resistor pads. We need those intact!
First let's do a little bit of preparation. In order to get the module working again we are going to have to recreate the connections that we just hacksawed off! These are the places we'll be soldering wires to so it will help if you just blob a little extra on these point before we start wiring it up.
While you're at it you may as well tin the connections on the 1/4 inch jack.
OK, first job is the trickiest bit. You might have noticed that along with the holes for the 3.5mm sockets we also lost a diode. We need to reinstate that as it's required for the switch on the MIC IN socket.
Take about 2.5 inches of wire, strip about 1/4 inch off the end and twist the strands. Then holding the wire as close to the cathode indicator (the black line), wrap the twisted wire around the leg of the diode.
Push the twisted wire in close to the diode body and then solder in place.
Now we need to solder one side of the diode (cathode) to the resistor pad on the right (looking at the back of the PCB) and the other side to the left hand resistor pad (which is in fact GND).
Lay the diode-wire assemble onto the PCB so that the diode legs are touching the solder on the resistor pads. Solder one side to hold it in place then do the other side. Once you're happy, snip the legs of the diode off at the soldered pads.
Next take another piece of wire, about 3.5 inches (you can trim them down later), strip and tin one end and solder to the solder pad in the middle of the 'h' of the word 'Thing'
Cut two more piece of wire, one red about 5.5 inches and the other black, about 5.5 inches. Strip and tin one end of each and solder to the MIC - (black) and MIC + (red) pads.
Twist those two last MIC wires together and solder here (black and red respectively). You may want/need to trim the wires a bit if they're too long.
Solder the other end of the first wire (the one attached to the 'h' of 'Thing') to the banana jack. Take the wire that is soldered to the diode and solder the other end to the leg of the 1/4 inch jack as shown. You might need/want to trim the wires before soldering.
Done! Obviously replacing the 3.5mm output socket with a banana jack means you lose the ground connection so you'll have to compensate for that.
Hope that's been useful!
Music Thing Modular mikrophonie mod SDIY banana