Korg Mr. Multi clone build.

[digi2t]

Hi all,

Well, I've been plugging away at a Mr. Multi (FK-2) vero clone. Here's some shots, so far;







and into a Crybaby shell...







I'm waiting on the footswitch right now, and I don't have the right zener, but it wahs, phases, and wah/phases nice. The drawing I found states that it should bias at 3.5 volts, but I only had 4.7v zeners on hand. It seems to work fine, but I've ordered some 3.6 and 3.9 volt zeners, to try and get closer to the spec. I'll find out what if any difference they'll make at the same time. I was REALLY lucky that I found a solder side picture, since both drawings that I found had the same errors insofar as the series diodes connections were concerned. I fixed this on the schematic, and vero, but I'll have to update the vero BOM in the gallery once I nail down the right zener. One thing though, I'm getting some really neat yoyoyo's  out of it though  . Once I get the switch, zener, and LED done, I'll post a video. All in all, pretty neat wah. Glad I built it.

I had also done a vero of the Keio Synth Traveller, which would have been next on the table, but I found some great stuff on the Korg FK-1 Synth the other day. It has the "Traveller" function, plus some others, as well. I'm thinking about doing a vero of the FK-1 instead now. If I can manage to stuff everything into a Crybaby, then I'm ditching the Keio for the FK-1.

[John Lyons]

Lookin' good! Cool build as far as the sound clips I've heard.

[Ronan]

That's really neat Dino! The switch wiring would have taken some time to work out, easy to make mistakes there. That multi-colored wire would help a lot!

[digi2t]

That's really neat Dino! The switch wiring would have taken some time to work out, easy to make mistakes there. That multi-colored wire would help a lot!

You're absolutely right Ian. I couldn't imagine doing this one with one color   . Even with the multi-color, I was having trouble getting the sweep right, and after walking away from it for a while, I came back to discover that I had the pot connections (including the taper resistor!) wrong. I'll have to make a note for anyone that's going to use a Crybaby as a home, to which side of the pot to place the resistor, and how to wire the pot to the switch. Where I went wrong was that I looked at a gutshot of the Korg, and place the resistor as per the photo, and schematic. The problem is that the Crybaby rack is located on the opposite side of the pinion gear, hence the pot rotation is opposite, low to high.

Through trial and error, I also figured out how to set the trimmer. It sets the low end of the Q, suiting the frequency to the sweep of the pot. That way you don't have to fiddle with the pot position too much. A multi-turn trimmer is ideal here. In auto mode you can really hear the sweep. I can't wait for my scope to arrive, so I can hook it up, and really tune it. I'll post a video tomorrow.

[digi2t]

Here's the video. I don't have the bypass switch yet. Details, details.... 

It's actually kind of cool when you max the LFO in Auto mode. Sounds like it's drowning  .

Enjoy.

[Mark Hammer]

Very nice build.  Those purple cable ties are dead sexy!  Nice demo video too; more explanation than wanking, which is a refreshing change from some things I've seen in past.

[digi2t]

Very nice build.  Those purple cable ties are dead sexy!  Nice demo video too; more explanation than wanking, which is a refreshing change from some things I've seen in past.

Thanks Mark. The cable ties came from ABRA in Montreal. 1000 ties, in 10 different colors, for 10$.

As for the wanking, I try to keep it to a minimum for these videos. After all, it's the effect's sound we're interested in, not my lack luster guitar playing  . Although, it's a shame that all my main gear is still packed away, and that I don't have a camera with better sound capability. Otherwise I could produce much better videos, with better sound depth. Oh well...

[Greenmachine]

Ha, I shop at ABRA too.  Stay away from the pots, but you're probably well aware of that. 

[Mark Hammer]

it's a shame that all my main gear is still packed away, and that I don't have a camera with better sound capability. Otherwise I could produce much better videos, with better sound depth. Oh well...

Not to worry.  When the things one listens for are aspects like the "fizziness" of an overdrive, or headroom of a gain stage, certainly better sound permits more valid evaluation.  When it comes to modulation effects, though, lesser quality sound does nothing to diminish what a person can learn about the LFO sweep, or the various features and options.

[digi2t]

The only pots I get from ABRA are the PEC pots, when space and application warrants their use. Actually, the pot in this project is a PEC 1 Meg linear, long shaft. I trimmed the shaft to size, and it fits and works perfectly in this application. I've used the PEC pots in 1 or 2 other projects, but usually their cost, and size (they're really big... and expensive) work against them. Really nice for a wah project though.

[Greenmachine]

The only pots I get from ABRA are the PEC pots, when space and application warrants their use. Actually, the pot in this project is a PEC 1 Meg linear, long shaft. I trimmed the shaft to size, and it fits and works perfectly in this application. I've used the PEC pots in 1 or 2 other projects, but usually their cost, and size (they're really big... and expensive) work against them. Really nice for a wah project though.

Yep.  PEC pots are certainly a quality component.

[digi2t]

OK y'all, the updated vero, and schematic, are in the gallery. Please note the wiring detail concerning the treadle pot wiring in the schematic.

Enjoy this really cool build.

Cheers,
Dino

[Govmnt_Lacky]

I'm really diggin' this project. Sounds amazing 

Is there a PCB layout for this? (YES... I know a vero can be converted to PCB... asking before doing  )

I notice that you say you are using a 1M linear pot. You also appear to have a resistor (330K?) in series with the pot. Was this for tone shaping OR was it essential for the overall pedal to function?

Great demo vid as well 

[digi2t]

Check in the gallery, I also have the PCB there as well. I don't have the capacity to do PCB's, but I've been adding them to the albums, if I come across them. Just be warned, I can't garantee that they are correct. I do use them to verifiy the circuit though, so technically, it should be fine. I used the Vocalizer PCB as well to verify that circuit, and it worked out fine.

As far as I can tell, the 330K resistor is a tapering resistor. It, and the B1M is true to the original. I guess it's something that you can play with to taste. Maybe replace it with a 500K multi-turn trimmer, and try fine tuning it. According to JC's schematic, you can also doodle with the phaser caps, but I find it sounds just fine the way it is. Actually, I found a great fuzz setting on my Geiger Counter yesterday, and ran it through the phase/wah setting. It just blew my mind man, it sounded just like my Uglyface, but now I could control the sweep.

Look in the gallery, under "Dino's Stuff", "Veros". My projects are in albums there.

[Govmnt_Lacky]

Thanks for the help Dino.

Unfortunately, I cant get to the gallery while on my work 'puter 

I will have to check it out later today. 

Now, I need to find a gently-used wah chasis and put this in my build cue!

[digi2t]

No prob Lacky. If you need them, I also have some gutshots, and pics of the board solder side. You can also check with my bro, pinkjimiphoton, he's got an original, if you need other info.

[digi2t]

OK, I fiddled with the 330K resistor on the treadle pot today, and guess what... it's gone. It is effectively a tapering resistor, but only when you're in PEDAL mode. From what I can see, the pot reverts back to linear to control the LFO speed, via the 2.2uF tantalum cap. I replaced it with a 500K trimmer, initially set at 330K, as such;



I then recorded the resistance across the two pot poles, in the toe down I had 255K, and in the toe up 122K. As I raised the resistance (in wah mode), I found the taper curve getting squished more to the toe down position. So, I started backing off instead. It allowed me to more or less line up the center of the sweep, with the center of the pedal travel. I've got a really nice hump now. My readings across the two pot poles are now; 40K toe down, and 71K toe up. From my rough calculations, I'm emulating a (approx.) 68K resistor here.

In any case, I highly recommend a trimmer, pot, whatever, here for the diy'er. It really allows one to refine the sweep of this pedal to ones taste. I'm glad i did it. I believe I'll just leave the trimmer here. I really like the sweep now, but I may just tweak it a bit more in the future when I incorporate it into my rig.

[pinkjimiphoton]

hey bro, sounds like your build you have the double wah and phaser reversed. you'll get a better wah if ya play with the pot and stuff...the wah on mine is pretty killer.

mine, the double wah nails a couple formants, the phaser sounds a bit different.

great build tho, well done!

will try and "up" a video so you can compare to the original if i can this afternoon.

it's REALLY REALLY close to the original tho!!

try it with the fuzz before it...seems to me to like it better that way.

[digi2t]

Formants... huh.

I checked all the wiring, and seems correct, except for the fact that I had to switch around the pot wires due to the pinion rack being on the opposite side. Like the original, the first position is phaser, then wah, and the third position is double wah (phase/wah).

Maybe yours has different caps? On the four "+" sides of the phaser opamps, the drawing I have has all 0.1uF caps. Can you check yours? Maybe it's got different value caps in there.

[Ronan]

+1 on the fuzz pedal first Dino. I find these phase filters vs band pass filters and resultant cool tones, wahs, formant vowel/dipthong sounds etc very interesting. I heard some formant type sounds coming from frequency central's Gemini Dual Core Phaser (on this forum), when he sets each phase core to the same LFO but one has an inverted LFO signal, and he offsets the range of one of the cores. All these circuits you guys are playing with add information and sounds to my pea brain, and something will evolve from it eventually (for my own sound search), the phase shift filters are drawing my attention and I ordered some LM13700 last night for some breadboard experiments. Your builds look very tidy Dino, nice to see. Thanks to Jimi for your input too.