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

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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bernhard42
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Post by bernhard42 »

Hi Jimi,

thanks!

I checked the boards from deadendfx.com, thanks for the hint. I guess the thing with the highpass buffer is too far from the original design, so i'll build mine from scratch on vero, i guess. And then the output buffer... i can't imagine myself successfully fumbling another opamp chip on a ready pcb...

Maybe you wanna wait for mine to work (or not ;)) before you start building yours - it's only simulation so far :D
Or do you build the deadendfx project as is?

I saw your video on the pedal.. really looking forward to having my own Mr. Multi!

Cheers

Bernhard
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PMowdes
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Post by PMowdes »

bernhard42 wrote:Hi Jimi,

thanks!

I checked the boards from deadendfx.com, thanks for the hint. I guess the thing with the highpass buffer is too far from the original design, so i'll build mine from scratch on vero, i guess. And then the output buffer... i can't imagine myself successfully fumbling another opamp chip on a ready pcb...

Maybe you wanna wait for mine to work (or not ;)) before you start building yours - it's only simulation so far :D
Or do you build the deadendfx project as is?

I saw your video on the pedal.. really looking forward to having my own Mr. Multi!

Cheers

Bernhard
I'm really interested to see how this compares to our version. The phaser and wah aren't great on their own, but in combo it really is a fun pedal. Let Dino or I know how it turns out and perhaps we can generate a pcb design if you are interested.

Phil
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bernhard42
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Post by bernhard42 »

Hey Phil,

thanks for your feedback!
I've started populating the board - still waiting for some parts though.
I'll keep you updated! When the pedal works I'll record something, and then we can see if it's worth its own PCB.

Cheers,

Bernhard
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pinkjimiphoton
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Post by pinkjimiphoton »

makin popcorn lol :popcorn:

i have a working original if any thing needs verification or anything. :horsey:

i have two versions of phil and dino's board, i look forward to getting it built soon. slow. i take forever.

but very curious to see how it works out!! :thumbsup
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digi2t
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Post by digi2t »

Phaser quality really depends on jfet selection. The tighter you can group the jfet's, the better the phaser will sound.

My first time around, I just threw a set of random jfet's in there, and it sounded like oatmeal.
No matter how many times I cut it, it`s STILL too short!

https://www.deadendfx.com/
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bernhard42
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Post by bernhard42 »

digi2t wrote:Phaser quality really depends on jfet selection.
Definitely. I'm trying homemade photocouplers with a suitable LFO this time though, as my parts bucket is full of LDRs from my last Non-RoHS-Parts-Go-Extinct-Panic-Shopping.

Matching applies in the same way, though i guess the parameter variations of LDRs are not as extreme as with JFETs. And the matching of LEDs can be done quite easily by running them in series - all with the exact same current.

Let's see how it works out... Still waiting for the mailman to bring the 4558...

Have you tried that phaser with some reverb back then, to get that true Hall & Oats sound? ;)

Cheers

Bernhard
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pinkjimiphoton
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Post by pinkjimiphoton »

reverb is a must always bernie ;)

sounds killer with reverb, you'll know ya got it when in double mode it starts going yoy yoy. its the formanty aspect that made me dig this circuit so much.

i gotta rully wow jfet matcher for doing this project, and a sack of 150 jfets to hopefully find a decent set.

still lurking, still makin popcorn :popcorn:
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Post by bernhard42 »

Hi altogether,

I could make some progress...

The filter works great - the combined wah-phaser mode is definitely the best!

Still working on the pedal characteritics with a whole forest of series and parallel resistors to the (orginal dunlop 100k) pot. Did i say i want to lighten the jungle a bit? ;)

And the lfo together with the photocouplers is still a bit too "univibe-choppy" for my taste.. maybe i've got to replace the capacitor buffer with some diode-feedback logarithmic kind of stuff. The control voltage span where the "whop" happens i realy narrow... at least the pedal is kinda useful already.

Ok then... Let's not talk about my attempts to fix in an envelope follower at this time ;) doesn't work at all yet.

I'm quite happy though with the non-feedback phaser sound. I tried to add feedback, but without feedback it sounds smoother. Just to my taste.

The wah is by far no as cutting as an inductor wah, but prnounced enough for my taste. I can't quite tell if there's a remarkable difference to the wah-sound of the original. I'll try to record something the coming days.

Still some way to go...

Cheers

Bernhard
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Post by bernhard42 »

Hi folks,

here's a quick update. I'm rethinking the LFO issue... Listen to my first simple tests with an Arduino Nano and PWM controlled photocouplers. No PWM modulation tone - I'm quite happy about that. The whole LED/LDR curve matching by software makes it easier for me as well.

In the file you hear some chords through the phaser, then the wah, then the wah-phaser. I fond I still have quite a bit of crackling in the wah modes... Hope I find a cure for it. Got one or two ideas...

Cheers

Bernhard
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