By Rob Hordijk, photography by Jan Punter
The joystick mod is quite simple but needs some very accurate tooling and it will definitely void your warranty. So think first before doing this mod. If you don't feel to shure about drilling big holes then better forget it, fat chance you mess up. Never blame me or anyone else, it is your own responsibility and if you mess up you have only yourself to blame. So think twice. The same goes for the soldering of thin wires.
First thing is to get a joystick module with 10kOhm linear pots, although 20kOhm pots will work as well. A small pot can be ordered from Farnell, although I used a Doepfer/Alps joystick for my NMK and for Wout his NMK. Jan Punter used the Farnell one which is smaller, perhaps it might just fit in a rack but we forgot to check. To be able to switch between knobs or joystick a button switch is needed, it has to be a double pole, single throw A|B switch, so one with six connectors, three for each pole.
A big hole has to be made for the joystick and another one for the switch. Before starting to drill the electronics board needs to be taken out. Do never, ever try drilling holes in electronic equipment if the circuit print is still in it. Imagine if a little slip of the drill happens and the drill goes right through the electronics. You wouldn't want that to happen, not? Only way to be sure that cannot happen is to take out all electronics first!
The joystick is mounted to the NM by four little screws, so these need to be drilled as well. When using a Doepfer joystick module the frontpanel of hat module can be used as a template to draw the holes at exactly the right places. The big hole is the difficult one as there are no drills to make such big holes, its about 24 mm or almost an inch. Best thing is to get a piece of _iron_ sheet of 1 mm thickness and practise first. Try making two or three holes. Then when you succeeded it might be time to drill the holes in the NMK case. Remember drilling has no Undo function. Use a oldsmith's saw or a big file to make a hole almost the right size, about 1 mm or 0.5 mm smaller. Then I used a corund cone to make the hole exactly round at the right size. With corund cones take your time and use only very little pressure, set the drilling tool to its _slowest_ speed (about 10 revolutions a second or less, this is very important, if you drilling tool does not know this speed, forget it, don't even try as a fast speed will definitely mess things up!), And if it takes fifteen minutes it just takes fifteen minutes. Just take your time and be patient. Applying pressure on a corund cone will only damage the cone and make it unfit to finish the hole, it will never make the work go faster! Let the weight of the drilling tool do the job. A bigsize felt cone with 'Paris green' polishing paste can be used to polish the hole. Or use a hardsteel polishing tool for the finishing touch. After the big hole is right mark the holes for the four screws and drill then as accurately as possible. If you don't think you can do this within a tenth of a mm accuracy, ask someone who can to do it for you. It is definitely important to get a really nice big hole and all other holes are exactly in place, it feels and looks so much better. An amateuristic looking hole might also lower the secondhand value of your NM drastically. Next the hole for the switch can be drilled with a drill of the right size.
Now put the electronics back in place. Lets assume that the joystick gets connected to knobs 1 and 2. Only the middle connection of the pot on the NM print needs to be cut, this has to be done very carefully with a small(!) and sharp(!) cutting plier. A big or blunt plier will damage the circuit board, so it is of the utmost importance to use the right tools. You really have to take much care to prevent the printed circuitboard from getting damaged!
First do knob 1. Cut the middle connection as close to the pot and as far away from the circuit board as possible. Two thin wires are soldered to both sides of the cut with a precision soldering device. Check that the soldering is clean and there is really no more connection where the cut and solderings were made. This is quite important because if there is, there would be a short circuit at the cut and if the knob is mooved fulle clockwise while th joystick pot is moved fully counterclockwise there is an electric short circuit over the power supply and the power supply gets blown up! And you wouldn't want that to happen, would you?
The wire connected to the print goes to the middle connection of one of the poles of the switch. The other wire from the pot goes to one of the outside connections of the same pole on the switch, the other outside connection on the switch goes with a thin wire to the middle connection of the X-axis pot on the joystick. The two side connections of the joystick pot are connected with thin wires to the two outside connectors of the knob 1 pot. The switch now gives a choice between knob1 or the X-axis pot. The same procedure must be done for knob 2 and the Y-axis pot.
That's basically all that's to it.
The joystick is reasonably fast. The values of the knobs get measured by the microcontroller in the NM. There is an algoritm in this measurement to prevent accidental changes of values due to eg crackling in the pots. This means that if the value changes the microcontroller does some more measurements and only if the next measurements measure the new or bigger values these new values are sent to the DSPs. So, after moving the joystick it takes a little while before the movement is heard, only a very little while, less than the latency of Cubase when I install it on my PIII 1gHz PC ;-)) But there is a bit the feel of latency on starting to move the joystick. When the joystick is in movement the NM reacts very fast, the joystick is much faster than the knobs. When moving very fast I think values are skipped but not more zippery noises than the knobs. I use a 6dB filter set to 12 Hz after the constant module that is controlled by the joystick axis. This removes all faint zippery that might be present and seems to give the cleanest control value. The smooth module is less useful, as it might zipper a bit. All in all I would say that the speed of the joystick is about 12 Hz or twelve times moving the stick from left to right in one second. One has to be a pretty hard case of ADHD to do so. :-))