Korg Mr. Multi clone build.

[pinkjimiphoton]

i will take a peak bro a little later when i got some caffiene in my blood.

eyes are REALLY wonky these days...so i'll try and see what the caps say.

but it's weird, your phaser setting sounds more like my double wah a little...maybe there's a mistake in the schem, or they're different revisions.

mine was maide by keio, if that matters..

gimme a little bit!

don't get me wrong, it sounds great!!

[digi2t]

Might just be hard to make out the difference in the video, due to my wonderfully crappy camera sound. This thing is just slightly above 2 tin cans and a string.

Seriously though, I'm pretty sure the wiring is right. In double mode, you can hear the two mingling together, whereas in the other modes the effects are apart. I saw the shot on Facebook of your board, and your's uses the chicklets, where I used ceramics in mine. Since the ceramics sounded so nice in my Vocalizer, I decided to go with them again in this puppy.

Do you think you could dust off your magnifing glass and give me the numbers off your chicklets? If there are any.

[pinkjimiphoton]

absolutely!!!

gimme a little while to wake up and suck down this vat of coffee, and i'll put on two pairs of glasses and find my magnifying glass.

you may be right, it could be just the video...

or it could be how the pot and rack is adjusted. at a gig last saturday, the dang pot fell out of the mounting....when i put it back, i didn't really spend a lot of time playing with the adjustment, but i've messed with it some in the past, and it seems to really rely on that adjustment. in the stock korg, there's  a stop for the pot tab to fit in which makes it a little easier as the pot only goes in one way, if that makes any sense.

gimme a little bit...i'm on it!

on mine, dual is kinda like a cross between the vocalizer and a wah, if that makes any sense...definitely can hear a couple formants happening, ahhhoooh to oooooheeeee.

[pinkjimiphoton]

circuit board  oriented with trimpot at upper right...

lower left chicklet h103k

4 on right h223k

coming off  the footswitch are some resistors, input y b o
out o o r

these connect to the fx select switch

there's a 2.2u @16v tant on the auto/pedal switch, too

hope this helps bro

[pinkjimiphoton]

video of mine uploading to youtube now.

here's two crummy gutshots...damn phone...

[pinkjimiphoton]

[digi2t]

Excellent bro, thanks.

I think you've got 0.022uF's (223) over the jfets, and 0.01uF's (103) across the opamps. My schem says 0.002 (202) and 0.1 (104), which I guess must be wrong, or just different versions to suit different IC's?

I did notice an error on the input cap, I put down 0.1, when it should be a 0.01. I have to fix that.

Could you do me a huge favor (again!), just do an inventory of the chicklets, and the ceramics. I mean, just get the numbers off them, and how many of each. As for where they're located, put the trimmer at the top, and go down each side, top to bottom. I'll be able to figure it out. I just need to compare between my two sources, and figure out what's what. It's a complex sucker  .

That is a mouthy sucker. Way mouthier than mine. I really need to get to bottom of this cap thing. I think it's really stealing the thunder from my version.

Thanks a bunch bro.

[John Lyons]

Dammit guys! Now I need to build this.
Great work Dino/Jimi!
This clip pushed me over the edge...need!

[digi2t]

Dammit guys! Now I need to build this.
Great work Dino/Jimi!
This clip pushed me over the edge...need!

I just updated my last post John. I just need to finalize the cap dilemma! Too many sources of information. 

[Ronan]

Dammit guys! Now I need to build this.
Great work Dino/Jimi!
This clip pushed me over the edge...need!

Yeah, same here. Really nice wah, and the double wah sure has some vowels coming forth, reminds me a bit of Peter Frampton with his voice box. Synthy too. Very, very nice. 5:30 and 12:44 on that clip are my favorite. Where do you guys find these pedals? I'm finding it interesting that formants can be created from bandpass filters or all-pass (phase) filters. I find I'm preferring the all-pass filters since they are not so "in-my-face" and have that phasey/synthy cool sound. Also I like the subtleness where some of the sound is left up to one's imagination, compared to say an eh talking pedal which certainly does the vowels, but could one use it all night at a gig? I don't know the answer to that, last time I played in a band was a year ago, my 50th, and the next band members 50th is a year away. Anyway, the Mr Multi is a real nice piece of kit, thanks for sharing and doing the clip Jimi, and the hard yards Dino.

[pinkjimiphoton]

thanks guys...i got it as payment for fixing a friend's amp. i had no idea what it was, i just wanted it, so he gave it to me...said he never used it, it was JUST a wah.,,,lol.

dino, i'll check ALL the caps for ya...it's easy enough to do. just gimme a bit, had a show last nite then had to drive another hour and a half in the wrong direction to bring grandpa steve home...got to bed around 5 am, just got up (1 pm here now)...so i gotta unload the car, and deal with a bunch of poo like this damned nor'easter that just has started, but will try and get at it today.

stay tuned my brother!! i think i can even read the codes off the trannies if need be; the two pair of reading glasses  and a magnifying glass actually works!! 

[the3secondrule]

sold. I have to build one of these. i've got a crybaby shell on the way, and was looking for something a little more out there than the standard wah.

thinking a bazzfuss built in could be  a good option, for some pre or post-wah dirt.

J

[the3secondrule]

Also, Dino - any chance of getting an export of the vero layout without components - ie just the jumpers / track cuts?

Cheers,

J

[digi2t]

Also, Dino - any chance of getting an export of the vero layout without components - ie just the jumpers / track cuts?

Cheers,

J

I'll do that for you tomorrow or Monday. I'm working 12 hour shifts this weekend, so time is tight. Can do though.

Cheers,
Dino

[Ronan]

I'm having trouble understanding how this pedal works in "double wah" mode. Can't quite figure out the feedback paths. I drew up a block diagram showing the connections when in double wah mode. If anyone can explain whats going on, I'm all ears.

Here's the block diagram.

Edit - I watched your clip again Dino, it seems to me the phase and double-wah positions are mixed up. There may be an error with the switch labeling on the schem.
If that is the case, then the simplified block diagram above would be showing phase mode as opposed to double-wah mode. Someone who is familiar with these circuits might be able to work out which mode the pedal is shown in above?

[pinkjimiphoton]

that's what i thought...i think the schematic, tho obviously close, may be a little buggy...or whoever drew it went with the values printed on the circuit board, which may or may not be right compared to the actual components listed?

tomorrow i'll get at them caps bro...

[the3secondrule]

I'll do that for you tomorrow or Monday. I'm working 12 hour shifts this weekend, so time is tight. Can do though.

Cheers,
Dino

Cool, Cheers Dino! no hurry on that man - this'll be one of my biggest vero builds so far, so i wanna make the best start i can.
Probably wont get to build this sucker for a couple weeks yet though, just planning ahead

J

[Ronan]

I will try your PCB layout Dino, ordered ua3403 and 2SK30A-GR tonight, give me a month to get the parts and build it and see what happens.
What does the 10K trimpot do Dino, set the sweep range? The schem says in regards to the 2SK30A-GR devices to "match the channel resistance for zero bias". Do you know what this means in practical terms? If its the same as matching Idss I can handle that. Maybe it means fit the devices and check for equal resistance from source to drain across each device, so use sockets on the PCB/vero, and for the same static control voltage, there should be similar resistance drain to source on each device? Anyway, will etch the PCB first and deal with the rest as it happens

[digi2t]

I will try your PCB layout Dino, ordered ua3403 and 2SK30A-GR tonight, give me a month to get the parts and build it and see what happens.
What does the 10K trimpot do Dino, set the sweep range? The schem says in regards to the 2SK30A-GR devices to "match the channel resistance for zero bias". Do you know what this means in practical terms? If its the same as matching Idss I can handle that. Maybe it means fit the devices and check for equal resistance from source to drain across each device, so use sockets on the PCB/vero, and for the same static control voltage, there should be similar resistance drain to source on each device? Anyway, will etch the PCB first and deal with the rest as it happens

@ Ian - I had another look at the PCB layout, and I noticed an error with one of the traces. I corrected it, and have uploaded it to the gallery, replacing the other one. PLEASE VERIFY IT YOURSELF AS WELL. You've been warned.

You were absolutely right, I had the Phase and Double Wah positions backwards  . Give to Caesar what rightfully belongs to Caesar, I humbly apologies to all that spotted that error.

As for the jfets, I did not bother going through the whole matching do-dad. I grabbed 5 of the cutest looking ones, and popped them in there (how I wish I could have said something like that back in college  ). R.G. does have a wonderful article on jfet matching here; http://www.geofex.com/article_folders/fetmatch/fetmatch.htm .\

Yes, the 10K sets the low end of the sweep. Too far one way, and you won't get enough low end. Too far the other, and you'll get a really hard WHUMP! before you get to the end of your heel down travel (hard knee). It's the Goldie Locks adjustment  . The way I set mine was like this; Using an audio generator, I pumped in an 800hz signal, pedal heel down. Turn the trimmer until you hear the signal get real low. It will seem as if going any further doesn't seem to make any difference. Now, start coming back slowly. As soon as you hear the signal frequency jump up suddenly, stop right there, you're home. From there, you can tweak it a bit higher if you like, but that's where I got maximum "mouthiness".

@ J - here you go (it's in the gallery as well);


@ everybody - The input cap value on the schematic, and my vero is wrong. It should be a 0.01uF, NOT a 0.1 uF. I don't know how or why that error came about, but I'm correcting, and uploading everything now. That's why mine didn't sound as mouthy as Jimi's. I swapped mine out, and it made a hell of a difference. It really opened the sucker up. New video below.

As for the other caps, I changed the filter cap from 33uF to 330uF. I re-examined the blurry pics and drawings, and came to the conclusion that just it's size difference alone would make it bigger than 33uF! The "0" is just really hard to see on the PCB layout, but it's there. There is a discrepancy between the jfet caps on Jimi's unit (original), and mine (clone). Where all my sources agree on 0.002uF's for the four stages, Jimi's seems to be using 0.022uF's. I haven't changed mine for the following reasons; Jimi's probably under 15 feet of snow right now, so I haven't had any confirmation on the numbers yet. Mine sounds A LOT better since I changed the input cap. Comparing Jimi's video to mine (now), we're not too far apart, although 0.002 and 0.022 represents a pretty big change. I get the feeling that maybe the 0.022's were adapted to suit the jfets in his pedal, whereas mine seem to work well with the 0.002's. In any case, here's a video of mine. I've changed the zener to a 1N5229, which brings my bias to 3.8v, the right input cap, 0.01uf, and a 220uf filter cap. I know the filter cap won't make a difference here, and I didn't have a 330uF anyway. Just thought I'd mention it. It's all updated in the gallery. Here's the result;

What do ya thunk guys?

[Ronan]

I think you got it pretty well nailed Dino! The only difference I can hear is the original seems to have a wider sweep range, more noticeable in auto mode, but Jimi would have a better idea on that than me. I checked the PCB, looks good to me, I know you are pretty thorough, will go ahead and don't worry no tears if it doesn't work. Since the vero is verified, I can check against that too if the PCB goes tits up. What a good find on the input cap value! I don't understand what the 0.002 JFET caps are doing, unfortunately, can't help with that one, unless I breadboard first.