[korg]
[ms]

User tips and techniques  ^

Here is the catch from a trawl I did of the Analogue Heaven archives for insider info and owner's tips on the MS Range.


André Majorel said this about controlling the pitch of the MS-20 with an external device, in this case an SQ-10 analogue sequencer:

"You have discovered one of the reasons why Hz/V voltage control sucks! With 1V/oct voltage control, to transpose a pitch CV, you can simply add another pitch CV. With Hz/V VC, you need to *multiply* your pitch CV by a factor. That requires a VCA.

Interval 1V/oct Hz/V
     
-1 octave - 1.0000 V ÷ 2.000
-2 semitones - 0.1667 V ÷ 1.122
-1 semitone - 0.0833 V ÷ 1.059
0 semitone + 0.0000 V x 1.000
+1 semitone + 0.0833 V x 1.059
+2 semitones + 0.1667 V x 1.122
+1 octave + 1.0000 V x 2.000

- You need a linear VCA
- Output of sequencer into input of VCA
- Output of VCA into VCO 1+2; CV IN of MS-20; KBD CV OUT of MS-20 into the CV input of the VCA.

I *think* that will work. :-)

n.b. the auxilliary VCA of the MS-20 is not the best tool for the job because its gain for a given CV varies with time (it's a
vactrol.)

André followed up these comments with this revised opinion, which may also be helpful:

- Output of SQ-10 into FREQ jack of the MS-20. Adjust the VCO EG1/EXT pot so that the SQ-10 pots cover the desired note range. If the SQ-10 has linear pots (i.e. the CV at the output varies linearly with the angle), this method is in fact preferable to driving VCO 1+2 CV IN : because the FREQ input is exponential (adjustable V/oct), dialing in the low notes will be easier.

- Instead of the FREQ input, you could use the TOTAL input and use all three MG/T.EXT pots. You will lose one modulation source on the filters but gain something that is otherwise unvailable on the MS-20 : keyboard tracking.


Jan-Hinnerk Helms sent this in via Analogue Heaven. More sounds on the MS Sounds page.

"As David Hillel Wilson pointed out [see below *], the MS-20's S&H works more like a Track & Hold, which allows for some nice things. Sorry if these have been mentioned before, but these were one of my favorite patches when I was a kid and deeply in love with my MS-20.

1) Poor man's Analogue Shift Register

KB CV OUT ---> S&H IN
KB TRIG OUT ---> S&H CLOCK IN
S&H OUT ---> VCO2 ONLY EXT CV IN

Tune both VCO to unison, make sure both are turned up in the mixer, set EG2 Release to 0, avoid excessive Pitch modulation to better hear the effect. Playing some notes gives this result:

- On each staccato keystroke, VCO2 will give the pitch of VCO1 from the previous keystroke. So you have to hit a key twice in order to make both VCOs the same pitch. Nice for canon-like melodies.
- If you play legato, only VCO1 will follow the notes you play, VCO2 will continue to play the pitch of the first note of your legato playing.
- As soon as you release a key, VCO2 will "catch up" to the current pitch of VCO1. To hide this, EG2's Release Time was set to 0.

"Poor man's Analogue Shift Register" >

2) Poor man's Duophony

Same setup as above, but now play legato, which will give this result:

- Only VCO1 will follow the notes you play, VCO2 will continue to play the pitch of the first note of your legato playing.

"Poor man's Duophony" 1 >

If you don't want to play legato, modify the patch like this:

MOMENTARY SWITCH TRIG OUT ---> S&H CLOCK IN

Now if you don't press the switch, everything works as normal. But for as long as you press it, you'll get this:

- The currently played note will be frozen for VCO2, your playing will only affect VCO1.

"Poor man's Duophony" 2 >

3) Autoglide

OK, this has nothing to do with the Track & Hold. Never mind, it's also fun.

KB CV OUT ---> MVCA IN
MVCA IN ---> VCO2 ONLY EXT CV IN

Tune both VCO to unison, make sure both are turned up in the mixer, set EG1 (Delay 0, Attack 2, Release 2), set EG2 to organ-like envelope with a bit of release to better hear the effect. Playing some notes gives this result:

- The frequency of VCO2 raises from 0 to the played note's pitch in EG1's Attack time, and falls back to 0 with the Release time. Especially nice if you set VCO2's waveform to RING. Ahh, memories…

Autoglide example 1 >


Autoglide example 2 >

Enjoy and best regards,
Jan-Hinnerk"

* "For the record, the Sample and Hold in the Korg MS-20 is not a sample and hold at all, but a related device called a "track and hold". As long as the clock input is high, the output will follow the input, allowing (for example) the white noise to run the VCO. When the clock goes low, it holds the value like a sample and hold. Thus you need a clock source that spends most of its time in one state, rather than a square wave as with a normal S&H. Fortunately, as Brandon points out, the MS-20's modulation generator can do this; You simply need to patch the square/pulse of the mod generator into the S&H clock and then turn the "Wave Form" control all the way in one direction [clockwise for the classic S&H effect.]

David Hillel Wilson
Curator,
New England Synthesizer Museum"


Here are some MS-20 patching tips, kindly donated by Gregg at Hermetech Records (www.hermetech.net/)

1) For steady drones you can patch Kbd Trig Out or ESP Trig Out to Initial Gain (but watch out for oscillator drift, about minus 1 semitone after 20 minutes, i learnt the hard way after recording 7 25 minute drones, and then very unsucessfully trying to put them together in AudioMulch!!!) If you dont want any pitch drift, then use the old sellotape/pen knife on a key trick!

2) Try patching SignalOut or Phones to Total/Frq/Ext Signal In/HPF Cutoff/LPF Cutoff/Initial Gain for crazy feedback paths.

3) You can also do very crazy feedback/oscillator stuff with the ESP, for example, patch ESP Signal In to Amp Out, then patch BPF Out to whatver you like, adjust pitch with the Signal In Level knob, and play with the BPF knobs for timbral control. For more of a square wave sound then patch ESP Signal In to BPF Out, and patch Amp Out to whatever you like, this time Signal In Level knob and the BPF knobs all effect pitch.

4) Patch EG 1 Out to EG 1 Trig In, and then patch EG 1 Rev Out to any input. Adjust EG 1 controls as desired for another variable waveshape and speed Oscillator or LFO. To take this further you could also patch Rev Out to Kbd Trig In, which also involves EG 2 in the equation, and patch EG 2 Rev Out to anything you like! Great for chaos patches!

Gregg's Patches:

Theremin


VCO's:
All off, no FM

Mixer:
All off

HPF:
Freq 0, Peak 0, no FM

LPF:
Freq 3-9 (controls pitch), Peak 7.5, MG/T.EXT 0.9 (controls vibrato amount), EG2/Ext 7

ModGen:
Waveform 5, Freq 4-5

EG1:
Not used

EG2:
Hold 0, Attack 3, Decay 0, Sustain 10, Release 3.

Patching:
Patch Phones to LPF Cutoff Freq. The waveform produced sounds (and looks) quite different to the normal self oscillating filter sine wave, and sounds closer to a real Theremin to my ears.

Notes:
For more craziness crank up the HPF Peak and twiddle the HPF Cutoff!


Chaos S&H (Subotnick-esque)


VCO1:
Tri, PW 7, Scale 4'

VCO2:
Ring, Pitch 0, Scale 2'

Mixer:
VCO1 10, VCO2 5

FM:
MG/T.EXT 0, EG1/EXT 10

HPF:
Freq 5, Peak 7, MG/T.EXT 0, EG2/EXT 0

LPF:
Freq 8, Peak 7, MG/T.EXT 0, EG2/EXT 0

Mod Gen:
Waveform 10, Freq 10

EG1:
Not used

EG2;
Sustain 10, all others 0

Patching:
Phones to S/H In, ModGen Pulse out to S/H Trig, S/H Out to Freq

Chaos S&H example 1 >


Chaos S&H example 2 >


Strings


VCO1:
Saw, PW 0, Scale 4'

VCO2:
Saw, Pitch (synced - as close as possible), Scale 8', 4' or 2' (Cello, Viola, Violin)

Mixer:
VCO1 10, VCO2 10

FM:
MG/T.EXT 0, EG1/EXT 1.2

HPF:
Freq 7, Peak 2, FM None

LPF:
Freq 8, Peak 4, FM None

ModGen:
Waveform 5, Freq 4

EG1:
Delay 1, Attack 3, Release 2.5

EG2:
Hold 0, Attack 1, Decay 1, Sustain 6.5, Release 3

Patching:
ModGen Tri Out to VCA In, VCA Out to Freq In

Strings example >



Earlier tips:

The Hz./V MS-20 is compatible with V/Oct. synths after all! -

"I can hardly believe no one knows about this already. It is possible to control an MS-20 from a V/Octave keyboard or MIDI/CV converter without a special interface. If you don't believe it, try it . .

When I first got my MS-20, I noticed that the filters don't track the keyboard at all. I plugged the keyboard cv to the filter cv in, but then the filter tracked the keyboard slowly in the lower octave, then went screeching off in search of tweeters to kill! I soon realised that the filter was tracking exponentially. I looked at the schematics and sure enough, both the VCO's and the VCF's have exponential converters on the modulation inputs. (You can tell this is the case, because the synth also goes radically out of tune when you plug the kbd cv to the TOTAL input, and wind up the MG / T.EXT knob in the FM section.)So, if you stick a V/OCT input into the modulation inputs and adjust the MG level for correct scaling, it all works and the filters track too.

Here's how you do it:

1. Plug the performance wheel into the keyboard cv input (middle, right) to disconnect the keyboard.
2. Plug the V/OCT cv from your MIDI/cv converter or another synth into the Total jack (top left).
3. Plug the s-trig. from your MIDI/cv or synth into the MS-20 trigger input.
4. Play a note on your MIDI keyboard or the controlling synth, and adjust the MS-20 performance wheel until you get a sensible pitch.
5. Adjust the VCO mod. levels until playing an octave on your MIDI (or other synth) keyboard gives an octave out of the MS-20. Then adjust the MS-20 performance wheel to coarse tune the MS20 and use the tuning pot to fine tune it.
6. The filter mod level pots adjust filter tracking in the same way.

You lose use of the performance wheel on the MS-20, but that's not a big problem if your MIDI/cv converter or your other synth has pitch bend. You will need a v-to-s trigger converter (i.e. the MS-02 Interface) to control the MS-20 from synths without s-trig. outputs, but they're simple to make (two resistors and an NPN transistor, plenty of circuits posted elsewhere).

I don't have the MS-20 in front of me, so apologies if the names of pots and jacks are not exact. Believe me, it does work!"

(from Steve Ridley)

Somebody else added:

"Beware of one thing... the VCF's are twice as sensitive as VCO's so that you must bring the VCF's mod pots to about 5 where as you would have the VCO's mod pot to 10.
I think this can confuse some people the first time they fool around... Actually, if one wants good VCF tracking one has to be careful in trimming..."


Dynamic ring modulation on the MS-20: yes, it can be done! -

>One of the things that still annoys me about the MS-20 is that all modulation of VCO frequency affects both
>oscillators equally. It would have been so easy for Korg to have two sockets for VCO modulation (like they did
>for EG trigger and VCO cv) instead of one. Without an extra socket, you can't control VCO detuning with an EG or
>the MG, you can't use the ring modulation for those spacey noises, you can't bend one VCO against the other etc.

"For your information, that feature comes standard on the unit!

Try patching the mod/pitch bend wheel to the VCO-2 cv IN. It is just under the Power switch/volume knob. Try that, hit that seemingly useless wheel and viola! - instant ring mod. gratification.

Also try patching any of the direct envelope outputs into the VCO-2 cv input; excellent for pitch envelope ring modulation. Note: there are two separate CV control inputs, one for VCO-2 cv 'as mentioned' and the other to control both VCO's 1 and 2."


Combining control or audio signals -

"Every time I encounter situation with the MS-20 where I wish I could do two things with one input, I usually solve the problem by simply using a two to one 1/4 inch adapter (I use the same adapter to split outputs as well). So in the case under discussion I'd say try COMBINING the wheel and keyboard cv's- it should track but I'm not sure if it will track accurately (there's no knob for the VCO-2 input and if it's not set up for the HZ/octave of the keyboard we're in trouble).

Meanwhile, back to the subject of mods.... an earlier poster wondered about VCO outputs, I'd love to know about this myself. Also has anyone thought about replacing/upgrading the incredibly noisy VCA?"

. . and you can use the junctions (a.k.a. multiples) on the MS-50 and MS-02 to 'split' a signal into 2 or more outputs, conversely.


More on control voltage scaling on the MS-10 & MS-20 -

"The 'total' and 'freq' input jacks on the MS-20 and MS-10 which control the oscillators' frequencies are scaled in V/OCT.

The only problem using these jacks with a V/OCT MIDI/cv converter is that the EG1/EXT. frequency modulation knob is not stable enough to allow the tuning to be set and have it remain stable. The synth runs from 1 V/OCT when the knob is about three quarters turned.

However, the knob is stable when cranked up full, but this results in the synth expecting an input of 0.8 V/OCT or so."

Another MS-20 fan added:

>Do you not also lose modulation possibilities? For example, if you use the 'Total'
>jack, don't you lose the ability to use the Modulation Generator for VCO FM,

Yes. But you could still route this to the VCOs using patch cords.

>and wouldn't the signal from the MIDI to cv convertor be routed to the VCF's
>also instead of the MG?

>Using the 'Freq' jack wouldn't you lose the use of EG-1 as a modulator?

Yes. But you could still route this to the VCO's using patch cords.

I see what you're getting at (that the V/OCT cv takes up a VCO control input, whereas the Hz/V cv does not), and I admit that the machine is really intended to be run by a Hz/V converter. I wanted to clarify that running it via a V/OCT converter is possible."

Korg themselves would of course recommend the MS-02 Interface for this purpose.


Controlling VCF Fc with external cv's -

"Anyway, one simple 'mod' that requires no work: insert a cable only halfway into the cv-in for LPF or HPF. This way the EG won't be disconnected when using external cv control! So an external cv signal controls the filters just like tweaking the 'cutoff frequency' knob. This'll often sound better than when the EG is disconnected."


Modding the MS-20 for PWM (Pulse Width Modulation) -

>I really missed PWM on my MS-20, but lazy as I am I bought an MS-10 to get it. There would probably be a market
>for someone doing these mods to the MS-20. It's definitely possible.

Ok, I have done that some time ago on mine. I didn't want to drill extra holes, so I decided to replace manual PW by PWM (ccw: fixed width, cw maximum LFO PWM). Its just two resistors, a wire and the cutting of a pcb connection. Everyone who has service docs could easily figure it out.

Anyway, I wouldnt do it again (though it works like intended). I miss *manual* PW a lot now (it is fun to modulate it real-time by hand), and with PWM I have to decide for one, hard-wired, PW starting point. (I always hated this approach on Roland synths: either PWM *or* manual PW. The main reason that Jupiter strings cannot reach Oberheim and Prophet strings, IMO)

I will recondition it to the original state some time. If only these PCBs weren't fixed with thousands of pots ... modding Korg MS synths is a pain!


What's that momentary switch for again? -

>I'm messin' with my MS-20 and decided to bite the bullet and try and figure out what the hell the button on the left hand side does (the little black one next to the mod wheel).
>I know it's assignable and I know it puts out something in the range of +3 or so, and it's probably a trigger of some sort but I have no idea what *use* this is.

"Well, what I've done with it was that I had some drum sounds coming through the ESP, but the trigger threshold level was kinda iffy. It'd trigger one of the envelopes, but barely. It'd play along just kinda peeping around for a while, then I'd have the (momentary switch) trigger out patched into the second envelope, to fully trigger it (usually at a certain point in the song). That's what I did with (the switch) anyway."

An interesting use for it I've found, is to trigger EG-1 to control VCA-2, and dynamically introduce pitch and/or filter modulation, governed by a noise source. Good for those underwater or space sequences in your next Discovery Channel/Apollo 8 documentary soundtrack. Here's the patching:

VCO 1 & 2: off (zero on the mixer)
VCO Frequency Modulation: both zero
VCHPF Cutoff Frequency: 0
VCHPF Peak: 0
VCHPF Cutoff Frequency Modulation: both zero
VCLPF Cutoff Frequency: 4
VCLPF Peak: 9
VCHPF Cutoff Frequency Modulation - MG/T.EXT: 8

EG-1 Delay Time: 2
EG-1 Attack Time: 7
EG-1 Release Time: 5

EG-2 Decay Time: 3
EG-2 Sustain Level: 5+
EG-2 Release Time: 4+

(Other controls are irrelevant.)

Patch Panel:

Momentary Switch to EG-1 Trig In
EG-1 Out to VCA-2 Control Input
Pink Noise to VCA-2 In
VCA-2 Out to Total In

Play a note, then push on the button. The filter modulation will fade in, and then fade out when you let go of the button (adapt this to modulate the VCO(s) in the same way.) Add SpaceVerb (tm), and Bob's your funny Uncle.

There's a million other uses for that little switch, this being two of them -

". . switching the lights in your room on and off, and of course launching a nuclear missile. This would however convert your Korg MS-20 into a piece of military equipment, so watch out how you handle it."


MS-20 power supply warning! -

"Being a cute little cheap synth, the Korg was bought by a lot of poor musicians. It's getting real popular again. It ain't built like no Moog. I suggest to all Korg MS owners that they pop theirs open and look at the power supply. There are two voltage regulators which supply 15v and -15v to the board. These regulators are held to a heat sink.....WITH NYLON BOLTS. Mine had sheared due to harsh impacts suffered in the past decade and also probably due to hundreds of hours of uptime heating up and corrupting the plastic bolts. When mine died, what had happened was that the bolt on the -15 unit had sheared and there was like a hundredth of an inch twixt the regulator and the heatsink. Regulator heated-heated-heated, and finally just started letting voltage thru the system. First thing to go was the gate controller on my Kenton; second thing to go was the opamp governing trigger behaviour on the HADSR and keyboard. Unit went to the shop where everything looked fine... We left the box on for a couple hours to burn in and "...hmm smells like burning chips..." by the time we tracked down the regulator problem it had fried about 6 or 8 components board side.

Nuff said? If you aren't skilled enough to do this yourself go to the shop. There's probably other things that were made to die inside this valuable little beastie. I've had my upgraded and replaced the 1/4" jacks with Switchcraft ones . ."


Using the ESP as a trigger processor -

"I also found a little cheat to make the MS-20 gate triggerable. Feed your gate into the External Signal Processor and voila... trigger out to trigger in and you're good to go!" (note: the gate must go down after each note or else the Processor won't trigger.)


Din sync mod on the SQ-10 sequencer -

There is no Din sync on the SQ-10, but it's a simple matter (for someone with a soldering iron) to build a converter output of 1 opamp (a 741, say) to convert Din sync output to trigger the clock of the SQ-10. (This is how I used to sync mine to Din sync, and hence, to MIDI through my Din-to-Midi sync converter).


Another view on the MS-20 in OCT/V mode -

As some of you may already know, the MS-20 can work in OCT/V mode. Use the VCO input instead of CV in. Adjust the potentiometer (VCO section, EG1/EXT) to around 8.5 - 9.2.


Anecdotally-

"I suppose I told the story already about the friend who sold 3x MS-20 synths, 3x SQ-10 sequencers, and the MS-02 converter in a swap for one (Korg) M1. Ooops."


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