KORG - FK-2 Mr. Multi Phase - Wah - Double Wah  [schematic]

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KORG - FK-2 Mr. Multi Phase - Wah - Double Wah

Postby modman » 24 Oct 2008, 10:38

Image

hadn't seen a auto/manual switcheable wah before, but hey...

From a current Ebay auction

4 bids in first 15 hours, 9 days to go... my estimate is at least 150EUR -- but perhaps there already is a schematic? No gutshots in that auction though...

mm
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby DiscoFreq » 24 Oct 2008, 13:31

Sssshhhhht, I'm the highest bidder :p
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby borislavgajic » 24 Oct 2008, 13:45

I had one in my hands.........years ago.......phaser is 4 stage FET phaser around quad op amp...I don't recall wah part........probably inductor(or mini trafo)......and sound was week( it was broken)....but intresting pedal :wink:

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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby analogguru » 24 Oct 2008, 15:37

There was a hand-drawn schematic and a pcb layout floating around for it in April 2007 (I think on the other forum).

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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby modman » 24 Oct 2008, 20:14

on diystomps I found;

Eb7+9 -- Re: Bi-Filter w/Hammer mods: Relatively subtle effect?
« Reply #1 on: 24-01-2006, 11:44:33 » wrote:
Quote from: bellyflop on 24-01-2006, 05:03:03 wrote:... definately not an in-your-face effect.


... the reason why is because there's only one stage of phase-shift - ok, there's two stages but they're running in parallel, so you still get 90deg shift max at any frequency ... you'll get more phase-filter depth if you wire the BiFilter stages in series with identical caps instead of in parallel with hi/low filter caps as Craig had in his original design (your choice on the cap values) ... if you want an in-your-face Phase-Filter effect you'll have to go with a four-stager like Korg's "Mr. Multi" ... I posted an un-official schem for it ...

~jc


On his website I only found a very nice demo of the pedal:

http://www.lynx.bc.ca/~jc/MrMultiDemo.mp3
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby Bernardduur » 30 Dec 2008, 14:39

I have one in now; will make some better pics + schematic

Can't find an inductor yet
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby Bernardduur » 30 Dec 2008, 19:05

Image
Image
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby Torchy » 30 Dec 2008, 21:48

The hard work we already did.
Individual images for diy pcb trace, layout, and schematics are here

The zip file contains all the above and an mp3 demo of the clone we built.

Mr Multi.zip

The mp3 file on its own is here MrMultidemo.mp3


Beware, this is not a "build-it-by-numbers" project. Results are superb though :mrgreen:
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby Bernardduur » 30 Dec 2008, 21:49

Thanks man!
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby Torchy » 30 Dec 2008, 21:52

No problem, hope it helps 8)
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby pinkjimiphoton » 12 Sep 2010, 20:11

hi folks, i'm a newbie here, and but an egg where building my own effects is concerned...

any chance some kind soul could re-up the schem for this old gem please?
i have one, would like to restore it to it's full glory, maybe add true bypassing...

thanks so much!!!

blessings

jimi
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah  [schematic]

Postby Hotrats » 13 Sep 2010, 13:37

needs some double checking around the switches ...
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby Hotrats » 13 Sep 2010, 14:01

.
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby Hotrats » 13 Sep 2010, 14:08

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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby pinkjimiphoton » 13 Sep 2010, 15:07

thanks so much!!!!!!!!!!
looking forward to getting into it more, seeing if i can restore it.
ya'll are "da bomb"...thanks again!!!!
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby theehman » 13 Sep 2010, 15:27

pinkjimiphoton wrote:thanks so much!!!!!!!!!!
looking forward to getting into it more, seeing if i can restore it.
ya'll are "da bomb"...thanks again!!!!


I picked up one of these a couple of months ago off a forum at a good price. It's really a cool pedal!
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby pinkjimiphoton » 13 Sep 2010, 15:29

i really like it, especially the "phasing" aspect of it.
if you tweak the pot a little, it can be a very usable wah, not as nasal and puky as the crybaby i modded.
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Re: KORG - Mr. Multi FK-2 Phase - Wah - Double Wah

Postby pinkjimiphoton » 21 Oct 2011, 04:59

just revisiting this...

i never really used it much, thought of it as a treadle controlled phaser.

but the double wah effect is very much a formant filter.

so..it's like an lfo or treadle controlled

wah

phaser

and formant pedal.

i have one of these, working, so if there's anything i can do to help make this thing cloneable for anyone, let me know and i'll do my best to gather info.

peace!
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KORG - FK-2 Mr. Multi Phase - Possible mods

Postby bernhard42 » 16 Apr 2018, 09:35

Hey folks,

first of all: sorry for unearthing this years old thread! I've been looking for a way to combine wah and phaser sounds for quite a while, and i'm really happy having found the FK-2. An empty Crybaby shell is waiting to get new guts on my working desk, as soon as a new coil of tin arrives by mail. Meanwhile, I simulated a bit in QUCS...
I just want to share my humbe ideas for mods for this lovely pedal, that may (or may not) make the sound more pleasing and may lighten up that switching jungle in the FK-2 a bit, making clone builds easier.

For reference, the schematic as drawn by JC Maillet:
http://www.lynx.net/~jc/MrMulti.gif

Changes to the JC schematic:

-Omitted the 220k and 330k feedback resistors. Similar to the Phase 90 "script mod".

-Changed the first OpAmp (Mixing Amplifier) to an inverting amplifier with a gain of -1 instead of +3. This increases the clean headroom of the filter, saves the inverting JFET stage at that point, and saves some coupling capacitors - the Opamp can be biased like all other opamps, so direct coupling is possible here.
Plans are to put a JFET input stage ahead of the whole thing, to get a decent input impedance suitable for guitars. 47k input impedance seems a bit low to me and might come from Korg's keyboard background...

-Phaser mixing network (2x 47k in my case, see schematic) is always connected. Doesn't do any harm

-22k Output feedback resistor in the wah modes (the one on the 4 pole switch) can be omitted - I couldn't see its benefit in the simulation.

-Wah feedback is not taken from the output of the second phase shifter stage, but from its high pass section. To do that, the high pass is buffered before connecting to the phase shifting mixer. See schematic.
My goal here was to get some degree of peaking lowpass character - similar to what I understand is the response of an inductor wah. The FK-2 originally has a bandpass response.

For simplicity in the simulation, i've placed resistors (zigzag symbol) in the filter instead of the JFET arrangement, to see the filter response at one given center frequency. I've chosen the bias voltage rail as ground rail - once again, for a simpler simulation. Cap values are also arbitrary. Soldering will show if I was right there...

Like this, for the mode switch, a 2P3T on/on/on ("Z type) switch would be enough, instead of a 4P3T rotary switch. More DIY friendly in my opinion...

The Wah feedback resistor is 33k in the schematic, as a moderate value. At 23.5k the resonant peak of the wah will be far into distortion - so for the first opamp a bipolar type like the 4558s might be a good choice for a somewhat graceful sound...
Lower than 23.5k, the resonant peak will get smaller again, and the treble rolloff will be stronger. Lower than 10k may not make much sense... For 33k, we have about 8 dB treble attenuation, should be subtly audible.

Missing in the simulation:
-Input stage and output buffer
-Bias voltage supply
-LFO
-JFETs/Vactrols/4 armed pot turning extraterrestrian minion/...

Hope this all is understandable. Feel free to ask back.

What do you think? Suggestions?

Cheers, Bernhard
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Re: KORG - FK-2 Mr. Multi Phase - Wah - Double Wah

Postby pinkjimiphoton » 16 Apr 2018, 20:29

kewl bern!! i am just getting ready to pop one of these... gonna put it in a fk1 shell

deadendfx.com has this as a project if you need a board... this is an awesome and useful pedal. soon as i clone it my original will be up for grabs
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