Korg Monotron

[petemoore]

http://www.ehow.com/list_7421127_korg-triton-specifications.html
 
  Interesting jobby, analog synthesizer.
  questions:
  Would this be useful for guitar [see below for *mod info].
  Is it a toy ? Is it too noisy to run a keyboard through or would I need a stereo bypass to use/bypass it ? [stereo output..
  Remarks: requires batteries unless PS is cobbled.
  *Has well marked PCB, so getting to the 'pads of interest' for ext. control and alternate functions, CV input etc. are all right there [albeit a very small unit w/very little room for 'extra anythings', one youtuber kindly showed how a 4 pin jack was managed into the case.
  Requires stereo support [don't know how much this matters, or whether the stereo 'L is different than R' each with different content.
  Don't plug mono sleeve into heaphone jack.
  I'm into techno for a short while of knob dialing [if I'm the knob dialer, and it's only once in a while...just for kicks mainly...I admit it can be mesmerising], whether the cool analog MS-10 filters would find favor [in terms of something I'd use] in the chain or simply find it's way into a box [with other box-on-shelf gadgets].
  Almost got one, tried it out with the teeny speaker and ribbon thingy, it didn't inspire much beyond 'fancy wierd toy', I'm sure it'd be more interesting with bigger speaker and input jack sourcing something with more pitch control.
  The youtube mods/applications certainly looked like fun.
  Seems like it could do really deep wahs/filter jobs with some control accesory-mods.
   

[Mark Hammer]

The Monotron contains the filter circuit of the original MS20: the world's most "dangerous" filter.  There is a line in jack for feeding an external signal to that filter.  However, for guitar-processing purposes, the user would need to:
a) supply a trigger and/or gate pulse to indicate when the signal begins and ends, if you're intent on having it sweep once in consistent fashion for each note,
b) supply an envelope follower or generator of some type to sweep the filter.

That being said, you can replace the onboard filter cutoff pot with a jack leading to an external expression pedal that can sweep the filter.

This thing has wads of fans world-wide and more modders than you can shake a stick at.

[Earthscum]

Came across this (not surprisingly, on Tim Stinchcombe's site, as I usually end up when it comes to synth stuff)...

http://www.timstinchcombe.co.uk/synth/korg.html

Just felt that link wanted a home in this thread. 

[Mark Hammer]

Thanks.  Interesting read.

[petemoore]

  Very good stuff.
  One thing that tipped the scales was my opinoin of how cool is it to mark the 'pads of interest' on the PCB: Too Cool.
  I haven't yet disassembled it [got is Yesterday], but I did look at some other disassemble-mod pics.
  Thanks for the tips/links and info ! I believe I'll do external control mod/chassis stacking or something before worrying about pluggin the guitar into it. Yupp...no-hands needed for controller is the way to go here.
  I plugged it in a stereo, and could get a few pretty cool usable 'things' from it, using the internal Osci, after a few twists [I plan to read the instructions etc. now..
  Then the Triton got plugged into it. Not too bad when the 1/8'' jack seems strong enough to make the lightweight unit...do aerial acrobatics.
  This weak point [one of the Idunno's I had about buyin' it, having had bad Exp.s with 1/8'' jacks in plastic like this, seems physically capabable of defeating the ''mass adversary'' [what teeny jacks face when installed in heavier units, they just can't lift 'em]. 
  Very profound effectages, I'm certainly greatly preferring this to building something like it [IIUC the MS-20 has Korg-oprietary chip in it [not otherwise available].
  Anyway, various types of profound efxage and musical notage' because the keyboard and ribbon can gang-control the synth.
  Basically the more sub-stantial/wide response type speakers open the effect up.
  It is merely a not very loud, non-extension kinda wierd toy otherwise, this.
  The small speaker served the music store and myself for the 'test that it works real quick'.
  Ribbon controller is ok as far as I know, looks/feels/acts like it could be the same ribbon in the Triton, neat-o for GoodVibrations [prefer longer ribbon I think] and cameo ribbon parts [perhaps even as part of rythm sections], the alternatives widen greatly when using the aux input and a more 'super-controller' controller such as a keyboard.
  There seem to be at least 20 ways to make it do soemthing else, filter-bender heaven.

[Mark Hammer]

Treat yourself to a youtube search on the Monotron.  There are some very impressive demonstrations of the power of this little party favour (small enough to come as a Crackerjack box prize!).

[lwatford]

It's worth it to use as a filter. I've bussed drums out to it and it works great. It's not that noisy, and there are all sorts of mods for it. Lots of fun in a little box. I don't know how close it is to a real MS20 filter (might be closer to an MS10 from what I've read), but it's great as is.

[Rodgre]

I love the filter in this thing. While it might be a little hissy when you run it into something like a mixer, amplifier or interface, it's worth it. Nothing sounds quite like the filter. I can't say that it is exactly as cool as the MS-10/20 filter, but I know that it doesn't sound like my Moog or Electrix filters. It tends to distort in a really great way. I use it occasionally in the studio to process other sounds. I also actually like it as a ribbon-controlled synth. Makes me not regret never finishing my old Paia Gnome quite as much.

Roger

[petemoore]

  There's a 'record output' mod, it takes the signal from before the headphone amp.
  The filters are very good as I understand and am beginning to appreciate.
  It makes a very good 'filters for dummies' learning tool [w/ MS-already].
  I'll have mull some more before getting out the paper and drawing it into a block/schem deal.
  Voltage control...I suppose there's various ways to do it, I'll probably start with a bit less than max input voltage and...see what that controls.
  Ribbon option alternatives [I have a lot of ideas here, starts with a wire, probably a connector, I'll have to measure the ribbon R and see what would fit...er...the ribbon is a variable resistor BTW ? [or is this what is called voltage control element ?...I'm lagging behind on my studies as you can tell.
  Just a little monster with various legs on it...not sure how they all need to be 'trimmed' or shocked.
  I haven't quite got ''Faith Healer" with it yet, the 'orb blip-drone' or the gnarl-wah lead parts, it feels close and like it wants to do that though...
  Any alternative to 'pot' of course qualifies as 'option'.

[Mark Hammer]

I love the filter in this thing. While it might be a little hissy when you run it into something like a mixer, amplifier or interface, it's worth it. Nothing sounds quite like the filter. I can't say that it is exactly as cool as the MS-10/20 filter, but I know that it doesn't sound like my Moog or Electrix filters. It tends to distort in a really great way. I use it occasionally in the studio to process other sounds. I also actually like it as a ribbon-controlled synth. Makes me not regret never finishing my old Paia Gnome quite as much.

Roger

There are apparently 2 MS-20 filters.  Tim Stinchcombe notes in a 2006 paper of his:
"The filters have a reputation for having lots of 'character', and if we attempt
to attribute this to some facet of the filters' topology, we immediately run into much
confusion: filters in the MS10 and early MS20s were built around a Korg-proprietary,
resin-sealed device, the 'Korg35'; in later MS20s, the filter was re-designed around
the LM13600 operational transconductance amplifier (OTA). Korg finally divulged the
circuitry inside the Korg35 in 2000, confirming that the filters' topology was indeed
one of the standard Sallen-Key types, as had been suspected for some time; the later
OTA-based filter however is basically two cascaded, buffered first-order sections, which
whilst still being a second-order filter, does not share the same Sallen-Key topology of
the original."

The 2nd OTA-based one uses a back-to-back diode pair - Tube Screamer style - in the feedback/resonance loop.  Small wonder people love how it sounds when you crank the resonance.