STIKKA Casio SK-1
Anti Aliasing filter bypass Mod
By Synchro November 2006

If you re-distribute this mod please do so as the original ZIP archive.
Disclaimer: If you break it, it's not my fault.


Sampling theory dictates that the anti-aliasing filter sits at around half the sampling frequency. In the Casio SK-1, which samples at the pathetic rate of 9.38 Khz this means that the reconstruction filter sits at somewhere around 4 or 5Khz, making it sound quite muffled & dull, not really what we want.

This mod bypasses the "melody filter" completely resulting in a much brighter sound.
Have a listen to the MP3, you can hear the preset sounds without the filter.
Much brighter, and some lovely buzzy digital grunge thrown in for free!

You only need to solder ONE resistor to one side of the board you have 2 options:


OPTION 1 COMPONENT SIDE:

The easiest way to do the mod is from the component side, follow the instructions
on the picture "SK-1-filter-bypass.jpg". Make sure the legs of the resistor don't touch anything! You could put some electrical insulation tape around it.


OPTION 2 PCB SIDE:

If you can't get to the component side anymore because you already have bends installed that prevent you from folding the SK-1 open, you can also solder the 1K resistor to the PCB side.  
"SK-1-filter-bypass-PCB-side.jpg" shows you where to connect it.

If you can still get to R41 and cut it, that would give you the brightest sound.
If you can't get at it, just leave it. The filter will still run in parallel with the mod but most of the signal will now go through the resistor.

Enjoy your new found frequencies!

Synchro.

              _______..___________. __   __  ___  __  ___      ___
             /       ||           ||  | |  |/  / |  |/  /     /   \
            |   (----``---|  |----`|  | |  '  /  |  '  /     /  ^  \
             \   \        |  |     |  | |    <   |    <     /  /_\  \
         .----)   |       |  |     |  | |  .  \  |  .  \   /  _____  \
         |_______/        |__|     |__| |__|\__\ |__|\__\ /__/     \__\

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