Korg M-500SP Mods1 - cykong.com

IEC Mains Inlet Connector

The M-500SP comes with a flying lead. There is not enough space to install an IEC Mains Socket.
So basically I cut the wire and put an IEC connector there....

Basic CV/Gate

I got the Analogue Solutions Socket Kit, which provides 3 sockets - CV/Gate/VCF.
Later I found that i shouldn't have got the kit because I do have enough info on adding external CV/Gate to the M-500/SP.

This is just BASIC CV/GATE in. There's an advanced CV/GATE mod which i plan to do later - it will provide CV Tuning and the Ext Gate will go thru the REPEAT circuit.

BASIC EXTERNAL CV IN

This is quite easy. On the Keyboard PCB, there's a 3 pin connector with ORANGE/BLACK/BROWN wires.

This is where the Keyboard CV goes to the main PCB. The ORANGE wire is the KCV.

So basically disconnect the ORANGE, connect it to a switch (see image on the right), and you have basic External CV IN!

BASIC EXTERNAL GATE IN

There are 2 ways of doing this. Either tap the Ext GATE to the leg of R65 OR to where R41/C63 joins.

Locate the Portamento Pot on the main PCB, you'll see R65 nearby.
Cut the bent leg of R65, scrap off some protective paint, and solder 2 wires there to a switch - see image above.
And you have basic External Gate In!

External AUX CV to VCF (Traveler)

Well...

Supposedly this should work.

Just wire the Ext Aux CV thru a 10R Resistor and tap it to PIN2 of the Traveler Slider.

I found this slightly sluggish, and it is not too smooth and the width of the VCF is not very full (also it will depend on the traveler slider position).

So what i did was, i added a switch, to switch between the 10R and NO 10R - ie direct tap to PIN2.

External AUDIO IN (Pre-Traveler)

I actually found somewhere that you can patch an External Audio signal into the M-500/SP - so you can have it going thru the Traveler VCF.

Basically the External Audio In is tapped to the Synthe2 output, so it then goes thru the VCF section. (Will only work if Synthe2 Button is selected).

I didn't note down what i did at the time, but when i'm doing the advance CV/Gate, I'll take some image and take down notes of what i have done.

Audio In socket is mounted on the side. I added a pot to control the input volume.

MIDI

At the time of modding the M-500/SP (back in Sept/Oct 2003), I was only just starting to modify synths.

Not having too much knowledge and research on Midi-CV, I installed a Synhouse Midi Jack II to the M-500/SP.

Basically, it's just tapped to the Ext CV/Gate sockets.

ISSUES

Disadvantages of the Synhouse Midi Jack II:

Does NOT support Pitchbend nor any other midi cc's.

No PORTAMENTO

You can tune the width of the CV range, but you can't really tune the CV...so on the M-500/SP, you need to transpose.....

Range is very limited - if i run the M-500/SP thru the CV/Gate sockets and use a Kenton Pro-Solo to drive it, the range is much wider...

So I am planning to replace the MidiJack II with another Midi-to-CV. But problem is i've already drilled holes for the MidiJack II mounting and config.... damn....

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Korg Micro Preset M-500/SP MODS 1
\| IEC Mains \| Basic CV/Gate \| CV to VCF Traveler\| Ext Audio In \| MIDI \|

Korg Micro Preset M-500/SP MODS 1