Sonic LAB: Korg MS20 Kit - Built and Modified

Full-size flatpack synth replica   04-Apr-14

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18:2 mins    

Last year the world went mad for the Korg MS20 Mini - a small scale reproduction of the classic analog monosynth, which by all accounts sells like hot cakes. Then at NAMM Korg introduced a full size, limited edition build it yourself MS20 Kit.

First major difference is that it's a much higher build quality, with everything bolted to to the front panel by 95 bolts (I should know, I tightened them all myself) it's a much sturdier machine. It's got the same electronics as the MS20 mini - including the USB/Midi interface, but with the addition of a selectable filter. The original MS20 had a rev 1 (Korg 35 chip) and rev 2 (LM13600) filter - the first was an angrier less refined design, the newer was smoother when fully resonant. These are selected by a three-pin jumper on the circuit board. Our first task was to attach  a switch to make it selectable externally. But first we had to build it...


Opening up the box it becomes clear pretty quickly that this is more of a self assemble project than a full DIY affair. We're talking screws, attaching some circuit board connectors and a LOT of nuts.

As you take out the tightly packed case parts and fully assembled circuit boards, it's does seem like a heck of a lot of stuff and at first appears a bit daunting. Though be comforted in the knowledge that while electronics boffins may be disappointed at the simplicity of the build, the novice should be able to take it on without distress.

Will It Bend?

The answer appears to be wholeheartedly yes, though please don't rely purely on my non-existent grasp of electronics. We modified the filter selection to be externally selectable with three wires and a switch, there are also many points labelled on the board for PWM, Osc Sync, individual filter and OSC outputs and more. Though I suspect you may have to start cutting holes in the case to access all of this stuff, it's most welcome (PWM especially).

The Build

I'm no stranger to flat pack, and this was no different, the instructions while occasionally puzzling, get you there with the application of some common sense. You would have to try fairly hard to break anything, with most operations simply a matter of lining up and screwing something in. The only tool provided is the spanner for the nuts, the rest can be done with a Philips (crosshead) screwdriver - absolutely no soldering needed.

Did It Work?

Well yes, even I managed it, we timed it at around 1hr 45 mins (not including a tea break). I took a couple of wrong turns - put the keyboard in the wrong way round and had trouble locating the foil end pieces. But at the moment of truth - when I plugged the external power supply in (the other deviation from the original) it powered up!

One other thing, the power will auto shut off if left on for a while - this I believe is a new EU eco power saving directive for all new electronic gear - but it worried me for a moment.


It does sound damn close to my MS20 original - given that its electronics are 30+ years old. I think I also now know I have the late style filter in mine, it seemed the closest - though the resonance kicks in earlier on my old girl. I was pleased to hear that there is a noticeable difference between the late and early filters when switching between them - the later one is smoother and less extreme, especially at high resonance settings on both LP and HP filters.

Paint Job

I noticed in the comments for the full timelapse video we posted, that there were questions about the paint work - some people have reported flaking of the white paint. I can unfortunately confirm that our MS20 kit also suffered from the patchbay area losing some of the white printed paint. This is a damn shame, and something that really should not happen. I would suggest a coat of some tough matt varnish or similar (you would need to research that). It would of course delay the final build - but believe me, you do not want to unscrew all those nuts.

Would You?

I guess, given that there are a number of options at this sort of price (£1000 UK, $1399 US) you have to ask yourself if you would - the more cynical might say "I have to build it myself and pay a premium?". Well yes, this is true, but it's a damn near perfect facsimile of an original MS20, for which one would expect to somewhere around twice the price.

Added to that it's a limited edition instrument and so does have a certain exclusivity.

I do wonder why Korg didn't include the filter selection switch as an option, perhaps a grommet on the panel to bolt it in if desired.

NOTE: it is possible to switch filters by a combination of notes (F#3, G#3 and A#3  for older, and F#3, G#3 and B3 for later filter) on power-up. It reverts to the hardware switch with no powerup modification.

The only real fly in the ointment for me is the issue with the paint, aside from that the build quality is solid (I should know, I built it...)

Limited edition - only 1000 available. £1079/ $1399

Available from local Korg dealers.


FYI Filter Mod Info

Its pretty simple, you just need a single pole, double throw switch, three wires and a Phobya 3 pin connector:
We used an old CPU fan power cable which had three wires and a connector. Then just wired up the centre pin to centre, each side to the outer pins of the switch -



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21 Comments... Comments are closed while we transition to Disqus

Goku    Said...

How do the keys feel?

04-Apr-14 12:12 PM

JB    Said...

Thanks for this Nick, top notch as per usual!

04-Apr-14 01:13 PM

Lu    Said...

Yeah it's supposed to be an improved keyboard on the original and the mini

04-Apr-14 01:14 PM

HT    Said...

Decals rubbing off so soon! Tut-tut

04-Apr-14 04:22 PM

LagrangeAudio    Said...

Lovely review Nick, nice work!! How did you do the slow camera tracking during the time lapse segments? That looked really good.

05-Apr-14 12:48 AM

rezleza    Said...

Great review! Thanks Nick! I just love the MS20 sound!

05-Apr-14 11:48 AM

Ms20 admire    Said...

Ok the famous technical question. What are the diferences between the Original, the Mini and the Kit in terms of behaviour sound, funcionality and the expandable options?

05-Apr-14 06:04 PM

Woo    Said...

Great overview. A shame though you dildn't do a quick compare to the sound from MS-20 Mini.

Ultimately I feel that this was Korg making a stunt-product for fetishists. What was needed was not a switchable filter (which only yields subtle differences) but better MIDI and PWM input (and maybe a Microbrute-like sequencer).

For the price of nearly three ms-20 minis (in the US, sale price) you get one reanimated old-style ms-20 that you have to put together. Not too impressed.

05-Apr-14 07:55 PM

E03    Said...

I have an original later model MS20 (bought back in '91) & i must say i still love it to bits. The modern equivalent's filter sounds very nary & cool, and the modding possibilities (osc sync & pwm!!)/filter switching are awesome options but i don't think i'll be selling my old girl for the new one soon. Saying that if i didn't already own one then i'd be very keen on this, albeit the build quality maybe a little suspect compared to orig. Nice review Nick - hope your hands have recovered after the assemble/disassemble process:)

05-Apr-14 08:32 PM

brianfromusa    Said...

So why do people like the early filter so much? The later one sounds a lot better to me. Now if only you could get that on the mini, eh?

06-Apr-14 09:59 AM

Woo    Said...

"why do people like the early filter so much?"

I don't think they really do. Besides, as we can all see from Nick's excellent video, the differences are quite subtle and in a mix they'd be pretty indistinguishable.

That said, it's the filter Korg used in the Monotron and they probably decided that to be most slavishly retro they ought to populate the mini version with the slightly dirtier filter (which they already had a ton of).

06-Apr-14 02:17 PM

Ben    Said...

Thanks for the review. Hmmm very annoying about the paint job and clunking oscillators. Hardly makes it a premium product. Mine came on Saturday, I wonder now if I should return it?

07-Apr-14 04:25 AM

brianfromusa    Said...

"Woo Said...

"why do people like the early filter so much?"

I don't think they really do."

You must not spend much time on teh interwebz. I've read plenty of postings from folks about how the Korg 35 filter is preferable, and most reviews of the mini call including the 35 "a good choice". I think what happened over time is modern MS20 fans actually like all the sounds that result from the many design flaws/quirks.

I'm pretty sure I could tell in a mix when the resonance is cranked, the earlier filter is very unruly, the later may not be "creamy" but it's an awful lot smoother.

07-Apr-14 01:57 PM

brianfromusa    Said...

"Ms20 admire Said...

Ok the famous technical question. What are the diferences between the Original, the Mini and the Kit in terms of behaviour sound, funcionality and the expandable options? "

Sound: no difference other than the differences betwen the filters. Mini is the 35 filter, original could be either and ONLY the kit has both.

Functionality: kit and mini add very basic MIDI

Expandable: original has different circuit boards and no marking, you're 100% on your own; kit has markings on the boards but you still must figure out the extra circuitry needed to implement any mods; until someone opens up a mini and looks at the board it's not clear if it has markings like the kit.

07-Apr-14 02:25 PM

Ms20 admire    Said...

So in terms of behaviour is almost the same, but the original are a bit instable. In terms of funcionality everyone are the same except the midi/usb signal. And finaly in terms of expandable options the kit have more options to expand. Isn't right?

08-Apr-14 01:14 PM

GTRman    Said...

Another piece of garbage from Korg. Who would want to assemble this? Even the screening is already coming off. Korg, stop putting out junk, we are not that stupid.

08-Apr-14 02:48 PM

abc    Said...

I have a production (or maybe just a wish)...

Korg will product an MS20 MKII or SE version. This will have the extra, currently un-used circuitry available on the front panel. Probably change an extra $1k

Who knows, you may be able to buy replacement panels when the white flakes off. Marketing 101 ;)

08-Apr-14 05:48 PM

The Guvnor    Said...

Excellent vid as usual.

What would be awesome is if Korg released the MS20 with an expander box to access all the additional functionality Nick was pointing out on the PCB. This could be plugged into the back of the unit so as not to mess with the design of the original.

09-Apr-14 09:11 AM

EMwhite    Said...

Hey Nick. Now you can get a job at the Moog Factory in Asheville, NC, USA. I've seen more than a few 'assembly' videos and you look to have it down.

Q: about quality of materials, do the plastics feel as 'good' as the original. Is the front panel metal or plastic for that mater (I've never met a vintage MS-20 in person).

As for all of the labeled points on the back; many of them look like test points (and labeled "TP") which are used post build to test and/or calibrate where appropriate. Not sure if there are a small handful or dozens of trip pots as you have not shown the topside of the board but if so, it is likely that factory workers calibrate certain aspects of the synth before boxing up. Having said this, I'm sure the tolerance of components is 1% or better (resistors) so maybe less tuning required.

As for the LM13600, it's an OTA, sort of a dual high-quality op-amp used loads in todays analog electronics, rather, the LM13700 is. Surely if Korg used it, it has been around a while.

Have a read here if interested:

Strange that Korg would have 'filled' the divots in some of the potentially usable mod points. Typically these are open holes. Biggest concern is the panel txt. Shame.

12-Apr-14 06:59 PM

Sander J Alkemade    Said...

great review.

But why is this thing twice as expensive as the mini ?

And is it worth the price ?

14-Apr-14 05:00 PM

Soundsafoolmusic    Said...

Why so expensive? 1) its not expensive at all. In real terms its cheaper than when the original came out. 2) A full size keyboard is always better than a mini (the keyboard feel on this is great). 3) The full size knobs are great/solid and allow me to twiddle without catching other knobs. The bigger knobs and the way it is built means there is no give in knobs and it will last a lot longer than the mini. 3) the full size 1/4 inch patchbay is magnificent. The larger sockets will be fair more robust than the 3.5mm sockets. Some functionality can be done by partially inserting the cables to a socket. This is so much easier to achieve in the kit than in the mini. The full size cables fit nicely with my full size korg monopoly. 4) it looks a lot less like a toy. 5) The completly different build quality than the mini means I am expecting it to be still working in another 30 years. Mini - unlikely that patchbay/knobs will still be working.. 6) With the bigger nice I could easily fit a IEC mains thingly to this and put the wall wart internal. 7) The circuit boards have marked points for PWM etc. Making it easier to mod. 8) The bigger back panel means it is easier to fit a dsub connector which I then connect to a disused altered patchbay to get access to all the mod points. 9) I put it together...

27-Jun-14 10:27 AM

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