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Axis-49 Revealed

 Ken Rushton - originally written March 2009, updated November 2010

    The Axis keyboards from C-Thru music are potentially the most keyboard innovative instrument to come out in several centuries (8 to be exact), for reasons discussed elsewhere on this site. No one else has the magical combination of velocity-sensitive, 2-dimensional array, ergonomic, isomorphic and inexpensive keys this thing has.

My gang of DIY music keeners (a.k.a. totally nuts music nerds) really wanted to see the inside of the new Axis-49. I volunteered to be the fall-guy.  So here is what I found.

1. Cute Feet.

The bottom of the unit has rubber feet that can be put in several places,
to stick out to a different degree and thus change the unit's tilt. This is a simple, robust way to adjust tilt that I wish PC keyboards had, as the hinge system many of them use is prone to collapse.

2. Clean PCB design.

The underside of the PCB is the expected simple design: no surprises here. Its basically a sensor array under the keys the detects the closing & opening of two switches under each key. The opening and closing of the switches is offset in time, and the difference in time is converted to midi velocity.


3. 2 Chips to run it all.

The whole thing is driven with only 2 chips, the USB interface is a PIC18LF2450-I/SO, and the dsp chip  is a dsPIC33FJ128 GP310-I/PT, a nice 16-bit, 40-MPS Microchip chip. Both chips are quality chips, and relatively expensive, I believe.

4. Inexpensive quality.

The buttons (technically membrane switches) are like the Yamaha DSP that I took apart a year or two ago. But these oft-maligned switches are much better, with real disks of graphite, and gold, not copper contacts. The thick membrane is probably high-quality silicone, which does not degrade with time. The throw is a decent 1 mm. not the .05 as in the Yamaha toy. I'm impressed. These should last many years and should always be accurate.

I'd have preferred a 2-3 mm throw, but 1 is acceptable.



5. Possible Key customization.


Finally, here are the key-posts. do not pull them off from the top - you may not get them fully back on the fastener, and may hurt the switch underneath. Instead disassemble the unit to get at the keys. 

Note that you should take great care in taking the top of the PCB. Turn the unit on edge, with the USB jack port on the bottom edge. Take your time.

Put the unit back together the same way, and ensure the membranes go all back exactly into place.

It should be possible to put in a light spring, felt washer or some such to quiet the keys, too.   



6. A modest Mod.

I re-arranged and partly recolored one bank of keys for playing in Wicki (folded major scale) mode. C in Green, E is dark blue. (The copper rod attached to the thumb is an experimental pitch and vibrato bending device.)

In summary, this is technically a very well built instrument.