Skip to Content

in​This​Project ( )

Korg MS-20 Serial Numbers and Characteristics

Posted under Early Korg Serials at . Last updated 2024-06-06 18:15.
Tags:Korg, MS-20, reference, history

Conventional wisdom has it that there were distinct versions of the MS-20 over time, the original having a pair of KORG35 chips on the KLM-127 board, but no supporting screw into the heatsink from the VCA panel [1]; the screw was apparently added after some time, and then for no very clear reason about a year later the filter was changed, with a daughterboard (KLM-307) being wired in in place of the KORG35s, using LM13600s. [α] While online comments sometimes say it’s not so simple, this often seems to be interpreted like there were specific points of change from early no-screw KORG35, to screw KORG35, to late-model LM13600. If so, it should be possible to use serial numbers to construct a timeline for the changes?

Examples Found

s/n [2] screw filter circuit voltage [3] description/source [4]
140014yes?220
140090yes?100
140097yes?100
140108no?1002023-07 eBay Japan. Duplicate sales — see Korg Duplicate Sales, MS-20 140108
140163no?1002022-05 eBay UK
140218no?100Also (a2) appeared here (same original source).
140255yes?100
140277yes?100
140353yes?100
140360yes?100
140363yes?100
140367yes?100
140400yes?1002023-12 eBay Japan
140419yesKORG35?A beautiful MK-1 original MS-20
140426noKORG35240 (mod)2021-08 eBay Australia; seller writes It is an early model featuring the OG Korg 35 filter.”
140438yesKORG35??The seller wrote: The Mk1 [ . . . ] i have owned both and did the test. What test? No other evidence, but chances are it is a K35.
140451noKORG35?100the MS title for a1 calls this a Mini but it’s not; reappeared (a2) with Early filter type, 2022-02 eBay Japan
140466no?100
140514no?117
140591yes?100?2022-08 eBay UK; reappeared (a2) 2023-04 reverb.com
140611no?100
140624yes?115 (mod)converted from 220/240
140645noKORG35240?2022-03 eBay UK; Vintage Korg MS20 mk1 with the sought after Korg 35 filter chips. 240v UK version; the pictures shown don’t actually show the voltage clearly — this may be a mod since it has the Keio Giken plate
140650yes??
140665yes?240Reappeared (a2) here shortly after, same pics.
140893yesKORG35?240 (mod?)2021-02 eBay UK
140895noKORG35230 (mod)originally 100V; early MK 1 model with the original and very sought after Korg 35 filter
140934noKORG35100Early MS-20 with the greyer faceplate and desirable Korg 35 filter type
141002no?100
141014no?100
141056yes?220?
141066no100also appeared earlier (a1) with fewer pictures
141104no?1002022-02 eBay Japan
141118noKORG35100Mark 1 / Korg 35 chip
141151no?117
141163no?100
141177no?100?s/n not visible
141213yes?100
141219yes?100previously 2021-04 eBay Japan
141256yesKORG352022-01 eBay Japan; Early filter type + picture
141272yes?117the s/n is not wholly legible, missing the third digit, but it could only be a 1
141317yes?220
141431no?1002023-12 eBay Japan
141445yes?1002022-12 eBay Japan
141447yes?100 (mod?)
141509yes?100
141532yes?100
141562yes??s/n not in pics
141567ano?100Two MS-20s with the same number — see Twynthesisers.
141567byes?100
141575no?100?
141576no?100Apparently also appeared earlier (a1) with the same ergonomic improvement, though at the time of writing in that post the serial number is not shown, though one of the pictures has a numberplate — but it’s of a Roland Juno 106S. (This may be a db glitch at Matrixsynth, as the picture also appears here.) Reappeared (a3) 2022-08 eBay USA (with s/n).
141595yes?1002020-12 eBay Japan
141605yes?100
141720noKORG35220at reverb.com mkI Korg 35 filter; modded
141747noKORG351002022-10 eBay Japan; Early Filter Type
141783no?1002023-12 eBay Japan
141800no?100
141822yes?100
141832no?100?
141846noKORG35117? (mod)original 35 filter version; seems to be modded from 100V
141954no?100?
141968no?1002021-04 eBay Japan
142002no?100
142018no?100
142029noKORG35240 (mod)2022-06 eBay UK; mk1 edition original Korg MS20 monosynth featuring the type 35 filter
142037no?100
142053no?1002021-04 eBay Japan
142064noKORG35117old filter; reappeared (a2) 2022-04 eBay USA
142090yes?240
142104no?117
142113no?117
142143no?240missing parts inc. ESP?
142145no??s/n given in text
142146noKORG35240KORG35 filter version
142273no?117fake wood
142283yes?2202020-12 eBay Germany
142292no?100
142319no?100?
142377no?100
142520noKORG35240 (mod)Type 35 Filter
142525yes?117
142542yes?117full set of images on flickr
142557no??s/n not legible
142560yes?117
142567no?1002021-06 eBay USA
142661yes?100?s/n not legible in pics
142659yes?100
142715no?117
142726no?117
142796yes?2402021-08 eBay UK
142810yes?240one replacement key; reappeared (a2) 2020 eBay UK; reappeared (a3) 2023-07 eBay UK
142811yes?240
142823yes??2021-02 eBay UK
142835yes??
142863yes?100
142874yes???s/n not in pic
142888yes?117
142899noKORG35220Première version avec filtres Korg 35; 2022-02 eBay France
142912yes?2402023-05 eBay UK
142939yes?2402023-01 eBay UK
142989yes?100
143005no?1002022-12 eBay Japan
143015yesLM13600230 mod2021-02 eBay UK. MK2 Seller claims to have changed the voltage tap, so has probably seen the KLM-307 board.
143063yes?220
143175yes?220
143281yes?100?s/n given in text
143312noKORG35100Early filter type; 2022-01 eBay Japan
143314no?1002021-01 eBay Japan
143347yes?100Reappeared (a2) here.
143356??100
143371yes?100
143376no?100
143418no?100
143473noKORG351002023-11 eBay Japan; MK1 Early Filter Type
143475noKORG35(mod from 100?)the earlier, grittier Korg-35 filter
143490no?1002021-01 eBay Japan
143502noKORG35120 modseems to be modded from 100V; This is the original vintage version, meaning it comes equipped with the legendary original Korg 35 filter. (Notice it doesnt have a screw in the center above the VCA graphic.) This indicates that it has the original filter which produces a much more aggressive tone than later models.” (This is marginally suspect and does not indicate that the seller has actually looked.)
143510no?100
143539???text-only reference
143555no?117
143566?noKORG35(117?)s/n might be 143565. Seller says (or quotes) that it has the KORG35 filter on the LPF . . . which implies that they haven’t looked, as it’s none or both, unless possibly modded. See also 144807 and 147963.
143657yes?100(a1) 2023-03 eBay Japan
143657yes?100(a2) listed shortly afterwards with new photos on reverb.com
143694yes?1002022-09 eBay Japan
143741yes?100
143763no?100
143820noKORG35220information from Michal Matlak
143980yes?100
144008yes?100
144075yes?1002023-09 eBay Japan
144132no?240
144219yes??s/n not shown in pics
144243noKORG35240Mk1
144340yes?240?
144419no?117
144461117
144468yes?220
144507noKORG35?220Mark I
144571no?220This appeared here with SQ-10 152096; they also appear in this post focusing on the SQ-10. The original seller claimed This MS20 is from the very first batch . . . ” but this is quite wrong.
144668yes?100
144677yes?100
144758yes?100?s/n not legible; reappeared (a2) here, still not legible (same pics).
144764no?117
144796yes?1002021-05 eBay Japan
144807yesKORG35117This seller is probably the same as that of 143566 and 147963, and uses some of the same text regarding the filter.
144809no?117
144812no?117
144890noKORG352402023-01 eBay UK; seller included pic of the KORG35 chips; may have had voltage modded?
144946no??s/n not in pics
145003no?100
145015noKORG351002024-05 eBay UK; seller photographed the interior
145022yes?240
145045yesKORG35?2402021-01 eBay UK. Mk1
145056yes?2402023-10 eBay UK
145063yes?2402022-09 eBay UK
145103yes?240
145125noKORG35?117Notice there is no screw on the VCA section panel.. this is an original 35 filter version.. known to be much more aggressive in tone and much rarer than the latter filters : ) The first assumption here is likely, but remains to be demonstrated, and we seem to be finding that the LM13600 is rarer.
145147noKORG35117This MS-20 includes the earlier Korg35 filter
145162yes?100
145169?noKORG35(117?)This MS-20 includes the earlier Korg35 filter
145174no??s/n not in pics
145213no?240
145268noKORG35240?2024-04 eBay UK
145326yes?1002021-03 eBay Japan
145359no?1002021-01 eBay Japan
145372yes?100Reappeared (a2) here.
145374yes?1002022-03 eBay UK; was 100V at this point but about to be modded for destination voltage
145452no?100Reappeared (a2) here a few months later.
145497yes?117
146529no?1002023-06 eBay UK
145565yes?240
145616noKORG35100a beautiful MKI MS-20 with the original Korg 35 filter design
145639yes?1002022-04 eBay Japan
145663???s/n not in pic
145695no?220
145773yesLM13600100Filter section does not use KORG35 chip. It has a filter daughter board.”
145914noKORG35100Mk 1
145930no?100
145968no?100?s/n not legible
145976noKORG35100Appears (a2) at the main link here with an SQ-10 (no serial number shown); they had previously appeared (a1) with no serial numbers at all here; the MS-20 appeared later (a3) here, with a photograph showing the interior. (No daughterboard.)
146025no?(220)This is a Swedish import (Matrixsynth says German, but no) by Hagström. Like other Hagström imports it has their own number plate, though in this case it seems that the original number was used, only prefixed with 53. The voltage will be 220 but is not actually stated.
146299noKORG35220information from Michal Matlak
146311no?220
146323no?100
146421no?117
146502yes?100
146504no?100
146513no?100
146530no?100
146537yes???s/n not in pic
146656yes?1002021-10 eBay Japan
146657yes?100
146739no?117
146774yes?1002022-07 eBay Japan. Duplicate sales — see Korg Duplicate Sales, MS-20 146774
146799yesLM13600100MKII Filter
146890yesLM136001002022-11 eBay UK; this is the MK2 original; replacement wood ends
146898yes?1002023-09 eBay Japan
146815yes?100s/n not in pics
146845yes?100
146861yesLM13600?1002021-01 eBay Japan. late model
146898yes??2023-02 eBay Japan. Duplicate sales — see Korg Duplicate Sales, MS-20 146898.
146971yes?1002021-01 eBay Japan
146984yes??100
146992no?2402021-01 eBay UK
146995yes?1002022-03 eBay Japan. Duplicate sales — see Korg Duplicate Sales, MS-20 146995.
147040no?100
147054no?100
147082yes?100?s/n not visible in pics
147114no?117
147120no??
147141no?117?
147239yes??100
147262no?220
147301yes?100
147324no?100modded
147325yes?240 (mod)2022-04 eBay UK
147345yes?100
147539yes??probably eBay UK 2020; vanished before I went back to check
147562no?117
147577no?117
147624?noKORG35117?Difficult to read s/n. Reappeared (a2) here with text. (This MS-20 has the original and legendary Korg-35 filter as opposed to the LM13600)
147677no?117
147735no?1002023-12 eBay Japan
147761yes?2402024-05 eBay UK
147765yes?2402022-08 eBay UK
147777yes?240
147855no?220
147882no?117
147888no?117
147891noKORG35?These pictures show a KORG35-version board without a daughterboard; pic 4 incidentally shows the serial number.
147918no?100
147945no?117Reappeared (a2) repaired here.
147963noKORG35117This seller is probably the same as that of 143566 and 144807, and uses some of the same text regarding the filter.
147965no?117full set of images on flickr
147966yes?100
147969no?117full set of images on flickr
147985no?117wood!
148015yes?100
148025yes?1002023-11 eBay UK
148029yes?100
148100yes??2024-03 eBay UK
148101yes??2022-12 eBay UK; the voltage seems to have been misstamped but is probably 240; being sold alongside SQ-10 152984
148126noKORG352202021-05 eBay UK; Here a rare Korg MS-20 MK1 release that mount the first filter release (KORG 35); full set of images on flickr
148204noKORG35220information from Michal Matlak
148358yes?100
148364yes?1002022-06 eBay Japan
148421yes?100
148457yes?100
148514noKORG35117original MK1 version with the 35 filter Reappeared (a2) shortly afterwards here.
148721yesLM136002202022-01 eBay Belgium. Modded with added amplifier & speakers. Cannibalised, missing several keys, pots, most knobs. (personally examined)
148727yes?100
148753yes?2202021-06 eBay UK; reappeared (a2) 2021-12 eBay UK
14EX8204n/a?240MS-20b (see Other Models below)
14EX8210n/a?117
148855yes?117?
148878no?2402020-11 eBay UK
148890yes?2402023-04 eBay UK
149126yes?2402021-05 eBay UK
149199yesKORG35?probably eBay UK 2020; vanished before I went back to check
149201yes?100
149206yes?1002021-03 eBay Japan
149245yes?1002022-01 eBay Japan
149286yes?240 (mod)2022-03 eBay UK
149352yes?220
149363yes?220
149394yesLM13600240Rev 2; 2021-05 eBay UK
149400yes?220
149411yesLM136002402023-06 eBay UK; reappeared (a2) with new pics from same seller 2023-08 eBay UK, and I believe this has the Mk2 Filter which does not hiss like the Mk1.
149500yesKORG35220(personally examined)
149534no?100?s/n not legible
149542yes?100knobs replaced
149560yes?100
149563yes?240 (mod)2023-07 eBay UK
149615yes??
149668no?2202022-04 eBay Germany
149744yes?2402022-08 eBay Australia
149762yes?220
149850yes?220
149914yesKORG352202023-01 eBay Italy; large VCO & VCF knobs replaced; filter information from Patrik Källback
149947yes?1002021-03 eBay Japan
149968yes?100Seller wrote Has the more sought after "screw"filter version.” It’s not clear what this means.
149984yesKORG35?220?MARK 1 VERSION. WITH THE (IN)FAMOUS IC35 SCREAMING UNIQUE AND TERRIFYING FILTER.”
Synthesisers have had some sort of cultural impact over the last sixty years, would you say?
439010yes?100
439021yes?1002023-12 eBay Australia
439039yes?100
439057yesLM13600100info. from Vincent Presley; this number later appeared here with wood ends and with MS-10 130492. (MS has the MS-10 s/n in the title which however refers to the MS-20.)
439078yes?1002022-12 eBay Japan
439093yes?100

(Total: 289. Last updated 2024-05-04.)

Interim Conclusions

Well, that’s a no. There seem to be some anomalies here, if we believe the story that the heatsink screw was added and then the filter was changed, simple as that.

Heatsink Screw

Clearly, the screw may be present at any point in the sequence. (Current totals: 152 with screws, 131 without.) Why this would vary as much as it does is unclear. Something to do with the weight of the heatsink? And that would perhaps be determined by the heat dissipation requirements of the voltage regulators . . . ? Strength of the boards used at different stages? Or perhaps it’s to do with the mechanical strength of the main attachment of the board to the panel, which is mostly via the potentiometers’ soldered legs; if the pot type differed over time, perhaps some legs might have been thought weaker. But on the basis of pictures I’ve seen (see Board Versions, below) of non-screwed KLM-127 boards’ component sides, there doesn’t seem like that much difference.

Filter Type

The 43s are strange representatives of the block, all found so far being over 439000, and all 100V; perhaps it started at 439001. Which would make sense since the lower 43s are occupied by the EPS-1. Presumably Korg planned to retire the MS-20 before the thousand was up. With those exceptions none of the numbers found are outside the 140001–149999 range, so production probably stopped at around 10,000 (plus perhaps only a hundred 43s, and perhaps minus an unknown number of 14- tuners?[5]). So there’s nowhere else for a significant group of MkIIs to be hiding. As some of the last of the 14- block are certainly KORG35, it seems that only some of the later MS-20s had LM13600 filters? And the earliest LM13600s started in the 3000s? Perhaps it was simply an availability issue rather than a design preference. [6]

There may be a reporting bias in these results — as the KORG35 filter has acquired a superior reputation, perhaps people are inclined to say that they have it for sale when they think they do, but people who don’t are inclined not to mention it. Probably several of the unknowns are in fact LM13600 but it’s impossible to say which. Even so, it seems that the LM13600 filter may be substantially the rarer of the two. Currently 9:48, but take that with a large pinch of something. And it should be noted that only a very few of these results are clearly demonstrated; some of them may simply be writers’ opinions, based on conventional wisdom about the relationship of screws and filters. [7]

I think it is possible to say that the KORG35 filter is not old or MkI in production terms, though it is the early design; but while it is a later design, the LM13600 board was only used intermittently. And it seems several KORG35s come later in the sequence than the last LM13600. (Update, 2023-04-07: We now have a confirmed LM13600 in the 439- block.) (However, in recent years Korg themselves have taken to referring to the Rev.1 and Rev.2 filters. Not, as far as I can tell, the whole synth, just the filters.)

Filter/Screw Correlation

So far — but this is a very limited sample size — all LM13600s identified have also had the screw; which might make sense in terms of the slight extra weight of the daughterboard, but it’s only about 40g. And it’s clearly not the determining factor in screw use. However, I can’t rule out the possibility that the first KLM-307s were attached by a different means to early-revision KLM-127s which did not use the screw.

Board Versions

At least versions C, D, E, F, & G of the KLM-127 board exist. I did think there was no significant distinction between them, but now with close examination — albeit with a small sample set of 1–3 each — it seems that:

  1. versions C through F have KORG35 chips and associated components on board, but version G has connection points for the KLM-307 board instead; and
  2. versions C, D, & E have no panel screw hole, but F & G do.

Unfortunately there are only three cases where I can directly associate board types and serial numbers — 147891 is version D, and the personally examined 148721 and 149500 are G and F respectively. It is unclear whether there may have been earlier boards with panel screw holes and/or KLM-307 connections, or whether these things may have been done differently. [8] But the first known serial numbers are associated with screws, and some LM13600s were used well before the only known KLM-127D. So these relationships remain tentative.

tentative summary of KLM-127 board revision features
CDEFG
filterKORG35LM13600
screwnoyes
known s/n 147891149500148721
sources [β],[γ],[δ] [ε] [ζ] PEX [η], PEX
Korg MS-20 Nº1 KLM-127F board, components side Korg MS-20 Nº1 KLM-127F solder side
KLM-127F, comps side (with front-panel spacer post) and solder side.
Korg MS-20 Nº2 KLM-127G board, comps side Korg MS-20 Nº2 KLM-127G solder side
KLM-127G, comps side (with front-panel spacer post) and solder side (with daughterboard connections and spacers).
(Here SW1, VR10, VR25, VR29 are awaiting replacement.)

The KLM-127 diagram in the (original) service manual does not give a revision number, but it appears to be earlier than rev.F at least. [9] (I would of course expect it to be the original production version rather than anything later, but who knows?) n.b. while the KLM-307 is sometimes described as a filter board, some examination of the service manual indicates that in rev.G, the VCA circuitry is also on the KLM-307 rather than the KLM-127.

Korg MS-20 Nº2 KLM-307 board comps side MS-20 Nº2 KLM-307 board, solder side
KLM-307, comps side and solder side.

(Update: Turns out VSE is now hosting a revised version of the MS-20 service manual with clearer diagrams and additional LM13600-version schematics and drawings. It distinguishes old production and new production KLM-127s but doesn’t give revision codes.)

There were multiple versions of the KLM-128 (patchbay) board too, though I’ve only seen rev.C, and I’m not clear what the differences were. The service manual for the MS-10 shows a revision of the noise generator circuit, with the revised version being the same as the circuit shown in the MS-20 manual. There is no indication that the circuit changed in the MS-20, but it may have?

An Unlikely Explanation

One possibility that should be acknowledged, though I don’t think it likely, is that the serial numbers are not a chronological sequence, but may have been assigned either randomly or by some other algorithm from within the 14- block. That would explain the above results, but still . . . 

There are two specific points of evidence for Korg using incrementing serial numbers in this period:

  1. The service manual for the MS-10 states that a change was made in the noise circuit, so that all MS-10s from 132828 had the new type — strongly implying a chronological sequence.
  2. The numberplate on Sigma 5663 appears to have been stamped twice with 5662 and then 5663.

And in general, some models with model-number type serial numbers seem to show (relatively) low production volumes with serial numbers concentrated at the low end of the number space, e.g. at the time of writing all BPX-3 serial numbers found are between 400001–401500 rather than randomly distributed from 400001–409999. As a back-of-a-spreadsheet calculation, the average numberspace proportion of the low-end and high-end numbers found (where >1 numbers known) for each model are at 0·044 and 0·489, which would be a −0·234 bias compared with random or other even distribution. I don’t think anything other than normal ascending incrementation is tenable for this time period.

(More recent manufacturing has been able to calculate and print quasi-random serial numbers with built-in validity-checks, but that would have been an atypical use of computing resources in 1978.)

Other Models

Several models of MS-20 have been produced, but this article is only about the originals, not the 21st Century models (MS-20ic, MS-20 Mini, MS-20 Kit, MS-20M Kit, MS-20M, MS-20 FS) or any future ones.

Korg did produce two models of large flat wall-hung MS-20s, for demonstration and teaching purposes. Model names are unclear — MS-20b, Blackboard MS-20, or Big MS-20 are used (see ref.  [θ]). Both were produced in very low volumes and I haven’t seen any serial numbers for the earlier version. The second version appears to have numbers in the normal sequence but with EX interpolated.

A Note About Colour

I have read some comments online to the effect that the case colours of MS‑20s varied over time between a blacker and a greyer colour. None of these comments cited any evidence. Photographs I’ve seen could be interpreted as showing a large amount of variation but these shots are taken in widely varying lighting conditions, with hundreds of different cameras, so it would be surprising if there were not some variation even without the possible effects of 40+ years of fading in different climates and state of cleanliness.

All I can say myself is that checking the colours of the clean undersides of all the MS- series devices I have shows that they are nearly indistinguishable from RAL 9017 in Northern daylight, but the rear/top/front panels (which could hypothetically have been affected by exposure) are a little lighter — lighter than RAL 9004, but not as light as RAL 7021 — and are perhaps a fraction bluer but that may not be apparent in warmer light. I expect the original colours were specified in the JPMA system. Instruments checked include an early-ish MS‑10 and a late MS‑20, so while I would be interested to see more evidence, a deliberate change during manufacturing seems unlikely.


Comment or Question about this page? write


Comments

Got an MS-20

by Vincent Presley on 2023-04-06 17:03

I just got an MS-20 and thought I would send you it's info since I found this article very useful.

Serial Number 439057
Has screw
100V from Japan
Confirmed it has the daughter board / LM filter by removing the side.

comment?

MS-20 149914

by Patrik Källback on 2023-06-18 21:05

New comment to Korg MS-20 serial no 149914.

Since it has a screw I assumed it had LM13600 OTA but after investigation I found out it has KORG35 filters.

(I'm a very happy guy!)

Greetings from a very summer warm Stockholm/Sweden

Cheers

Patrik

comment?

a little contribution

by Michal Matlak on 2023-08-25 18:20

Hi there,

a little contribution to your MS-20 MK1 MK2/Filter versions list.

I will have quite some more but it will take a little time to get them all together.

I am repairing synths for some years now and I documented everything.

Here are three I can confirm right away:

  • 143820 | NO SCREW | KORG35 | 220 | Owned by Werkstatt Matlak
  • 146299 | NO SCREW | KORG35 | 220 | Previously owned by Werkstatt Matlak
  • 148204 | NO SCREW | KORG35 | 220 | CONFIRMED* pictures from seller

Greetings from the Bavarian alps
Michal Matlak
www.werkstattmatlak.de

comment?


Notes

  1. Or, it depends what you mean by conventional wisdom. While compiling this page I came across this classic seller misrepresentation at Matrixsynth (my emphasis):

    Originally, the filters used Korg's proprietary KORG-35 chip. Later, the filters were redesigned to use off-the-shelf LM13600 OTAs. MS-20 fitted with LM13600 filters have a small daughter board. This one here has the later filter (the small screw above the VCA graphic on the outside it's a newer filter, if it has no screw it's a korg35. That screw is what holds the daughter board for the newer filter. )

    (source)

    This is quite wrong, but it does seem to be a popular belief. In reality the screw is into a spacer post, the other end of which is screwed through the heatsink for the power regulators and the KLM-127 board. It may assist in supporting the slight extra weight of the daughterboard (which is affixed to the KLM-127 board with plastic spacer posts) where present, but the screw is clearly used sometimes whether or not there’s a daughterboard, for unclear reasons. Consequently the screw does not indicate LM13600s, and assertions of its presence on this basis are wholly unreliable. To check, all you have to do is unscrew the left end panel and look inside; if there’s a daughterboard connected to the back of the main (KLM-127) board under the heatsink, it’s LM13600-based; if not, KORG35:

    Korg KLM-307 board end-on  
  2. Serial numbers have links where the sources are quasi-permanent. Where there are no links the online appearances were ephemeral, but I usually have the original photographs saved. Sometimes the source gives a serial number in text but not in pictures.  
  3. I’ve been collecting voltage information where possible on the basis that it might help to establish batch relationships or national-market differences. So far this does not seem to be telling us anything for the MS-20s, but who knows?  
  4. Some sources are given as year-month, eBay, country of sale, but it should be noted that occasionally the location of sale items is not given in eBay listings, only the seller’s nominal business location. In some instances the instrument and even the actual seller were elsewhere, perhaps in a different country. As I usually only check the UK eBay it’s the default.  
  5. 14- numbers were used on some GT-6s, and on at least one (presumably more) Micro-Six. See Early Korg Serials §Model Numbers.  
  6. Tim Stinchcombe (2006) [ι] suggested that it was to do with CV bleed-through in the KORG35 chip, or the cost of matched transistors. Unless the former was intermittently fixable it seems unlikely, as there does not seem to have been a single replacement event. The latter may be true to some extent, as it would simply be a cost→availability issue, which might have varied over time.  
  7. However, these opinions contradict and may cancel out. As an example of how disconnected they get, at June 2024 someone is selling an MS-20 on eBay UK, at about twice the usual price, with the claim:Serial number is below 150k which indicates that this is the Mk1 model with the better filter.” When in reality almost all original MS-20 serial numbers are in the range 140001–149999 including most of the LM13600 filter models. The serial number is not given in this listing; perhaps the seller feels they have something to hide anyway.  
  8. It may be worth noting that the KLM-307 board uses three standoff posts rather than the usual one per corner, as if the designers were working with the constraint of the existing KLM-127 design rather than taking an opportunity to change it, although revision G does have several changes compared with C–F. If rev.G was the only board used with the KLM-307, we might expect that the redesign would have incorporated all changes on the board itself, but it seems possible that rev.G is a later redesign intended to streamline production with a prëexisting KLM-307? Use of the KLM-307 with an earlier revision KLM-127 (A or B?) might also explain why rev.D was in use so much later than the earliest LM13600s?

    (Update, 2022-04-17: Some further examination suggests that there may have been a revision of the KLM-307 board, as seen at Studio Repair, as compared to my board which is presumably the original design but has some added signal coupling capacitors which appear to have been incorporated into the revision. Perhaps even earlier MS-20s didn’t have these? However, it should be noted that both these KLM-307s are used with KLM-127Gs.)

    (Update, 2022-04-20: There’s an image at synthesizor.wordpress.com which shows a KLM-307 with the same components and screening as the SR one, which has a screened code KLM-307A.)  

  9. As far as I can see, the diagram has C6 and R126 which are absent on the rev.F board, and the board has a D40, D41, R201, R202, R203, R204, R205, R206, R207, C50, C51 and C52 not on the diagram. The rev.G board also has these changes, along with others relating to the shift to the KLM-307. Also, R123 is in a different position on the KLM-127F compared to the diagram but absent on the rev.G.  

References

  1. Nearest thing to horses’ mouths on this would be: Korg Inc., Interview with Mieda Fumio and Nishijima Hiroaki, MS-20 designers, 2013 (YouTube).  
  2. Pictures at Matrixsynth Flickr  
  3. Pictures at Matrixsynth Flickr  
  4. Pictures at Korg Kornukopia  
  5. Pictures by Synthfool  
  6. Pictures at Matrixsynth  
  7. Pictures at Studio Repair  
  8. Alex Ball, The GIANT Korg MS-20, 2023 (YouTube).  
  9. Stinchcombe, Timothy E., A Study of the Korg MS10 & MS20 Filters, 2006 (updated 2009), available at timstinchcombe.co.uk.  

Article text ©2022–2024 Electropict Creative Commons Licence.
Click images for individual licences.