World's first Kawai K3 Hardwareprogrammer

Video:

Technical

i always dreamed of a hardwareprogrammer for my beloved kawai k3m. i love its sound but the programming is enoying. By chance , i stumbled over this old phatboy for about 40 eur. After looking at the parameter it sends (quite useless fixed dataslider/midicontrollervalues) and it's inner life (high quality hardware) i wanted to reconfigure this obsolete gearpiece into something unique and useful.

It saves a LOT of time and effort to already have a project-similar case, pots and pcb than to start from scratch.

Inside

The inside was encouraging: it showed a 6n136 optocoupler going into a µcontroller, some latches, a counter for the multiplexer, the eprom with the software for the controller and 2x4051 multiplexer. Also a nice 4 bit encoder to set the midichannel directly, wow.

I cut some wires on the pcb to put latch, eprom, controller and counter into eternal sleep. I don't need them anymore. I dont know the onboard controller and i dont want to reprogram it or reburn the eprom. I dont even know how to do that.

New brain

So i added a little piggyback with a atmega8. Also added a bicolor-LED instead of the default red one. The new led can shine in green, in red and (if both are on) even ORANGE :P  ... we need the 3 colors later for displaying the 'synthoperator' in which mode we are.

I then connected the atmega to the switches, both 4051-multiplexer and the midi-in and out. Had to put a 10k-pullup on RX to get the 6N136 to work on the mega8, stangely the former controller worked without.

Later i also added another pot for volume. Quite important on the k3 because when pushing up resonance the level gets quite weak and must be cranked up to keep average loudness. The second 4051 still has 2 open wires where 2 additional pots could be connected. But the case is already full. And i dont like to put pots on the cases side or back.

Colorcoded parameters

After a couple of hours for thorough frontpaneldesign and some µC-programming the Hardwarecontroller was ready. The panel is a simple color laserprint, glued on the case and sprayed clearcoat.

As you see, the parameters are colorcoded, most pots have more than one duty. To the upperright is a tripleswitch to select one of 3 modes: orange, green and red. When set to Orange, the LED shines orange and the orange parameters on the frontsheet are sent to the k3, mainly Envelope parameters.

When set to green (middle position), the led shines ...eh... green, yes. And the green parameters are sent out like waveforms, chorus, keytracking aso. Red Mode is for LFO and some leftover parameters.

The only 2 Parameters i didnt get under the matrix were 'Pressure to VCA and 'Pressure to VCF' ... no more pots left over. If i will ever need these 2, i will have to use the standard K3m frontpanel, well, that will do.

There are 4 white parameters which are ALWAYS sent, no matter which colormode: Volume, Cutoff, Reso and VCF-Envelope Amount. I find this quite useful and obvious.

Finished

So thats it. World's first Kawai K3 Hardwareprogrammer.

All incoming data (Notes Velocity, Modulation, Pressure) is of course sent through untouched and merged with the sysexdata of the pots. That means, the controller will be switches between midisender and the k3 and the k3 can be played just normal way - plus the pot-interface.

On extensive tweaking WHILE receiving notes, there are some note hangings now and then (approximately every 200th note or so). I guess this might be prevented but it would cost some additional hours of programming ... i am lazy and i dont mind about that... for the hanging notes i reconfigured the leftover 'snapshot'-switch to send 'all notes off' to the kawai.