How to tune Korg Micro Preset M500

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snod_donkey
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How to tune Korg Micro Preset M500

Post by snod_donkey » Thu Dec 15, 2011 5:37 pm

Just picked up a Micro Preset m500 but it wants a bit of a tune up

I cant find any set up info on how to set the volts per octave (if thats what it uses) or which trimmers to use.
If i set A to 440 hz and then press a note one or two octaves up or down the scale is not tracking correctly. Looked at the circuits but the quality is so bad i cant work out whats what

Any help would be great...

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gearfixer
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Re: How to tune Korg Micro Preset M500

Post by gearfixer » Fri Dec 16, 2011 10:00 pm

snod_donkey wrote:Just picked up a Micro Preset m500 but it wants a bit of a tune up

I cant find any set up info on how to set the volts per octave (if thats what it uses) or which trimmers to use.
If i set A to 440 hz and then press a note one or two octaves up or down the scale is not tracking correctly. Looked at the circuits but the quality is so bad i cant work out whats what

Any help would be great...
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gkmaia
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Re: How to tune Korg Micro Preset M500

Post by gkmaia » Tue Mar 17, 2020 7:56 am

This is quite an old post, but will see if I can revive it.

I finally finished fixing my M500 and now stumbling on how to tune it. My biggest problem is that I am out of range.


Vr1 seems to be a secondary VCO tune from keyboard
Vr2 tunes the VCO (frequency)
Vr3 tunes the trigger, but also affects frequency
Vr1,2,3 combines intends to tune octave 2"

Vr4 & 5 adjust the white & pink noise volumes

Vr7, 8, 9 & 10 tune the octaves 4,8,16,32 respectively

If I set the Pitch knob to "0" I should be able to by adjusting Vr1,2&3 get a C note on octave 2" close to tune and then use Vr7 to 10 just to fine tune the octaves.

But that is now what happens, even lowering down Vr 1 to 3 I still above a C.

I could change VCO's R27 & 28 to a lower value to force the opamp to a lower pitch but not sure if changing the circuit is the way to go.

What you guys suggest?

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