AionFX Viridian (BJFE Little Green Wonder)

MichaelW

Well-known member
Build Rating
5.00 star(s)
And the beat goes on.....latest in my Bjorn Juhl deep dive.

This is Bjorn's take on a Tube Screamer. I was really curious what he would do to this circuit.
Well, let me start by saying.......it's still a YATS..... :ROFLMAO:. I'm not sure if the Mad Professor version (Green Wonder) made it less "YATSY"
but there's no doubt this version has the familiar mid range hump and "closed-ness" of a TS808.

Having said that, there's also some hallmark BJFE elements, first of all, as an opamp drive, his choice of an LF353 makes a pretty big difference in how the gain structure sounds. There's the unmistakable "chewy" aggressive "angular" gain. (As opposed to smooth and symmetrical) Also the tone control is called "Body" and it's pretty wierd how it works. It's like from CCW to noon it acts like a Timmy-Zen bass control then from Noon to CW it acts more like a treble control.

It's made even wierder because I did not have an A100k dual gang and substituted a C100k Dual. But it works fine, all the tones are in there albeit the taper is a bit off. Actually, I rather like the C100k here as opposed to the A100k. (The original pedal uses a B20k Dual Gang but these are hard to source so Aion made provisions to use the easier to source 100k dual pots).

My initial impressions when I plugged it in was a little bit of a let down. Not sure what I was expecting, but the more I play with it, the more I'm starting to dig it.
It does all the usual TS stuff, like rolling off the gain and rolling up the volume it can push an amp or other gain pedal well.
But turn up the gain and it "sounds" like you're kicking in some clippers but there's no toggle. Just a pair of green leds in the circuit. It can get pretty aggressively gainy all on its own.

I'd love to see @Robert do a project on the Mad Prof version of the Green Wonder.

So a couple of misadventures in this build, I didn't have a green enclosure so I used a bare enclosure and painted it with my duck boat camo green paint.
It came out perfect and felt dry. By the time I had finished assembling, I realized the paint was still soft and I had scuffed it up....sigh.....I'm down to two more bare enclosures then I'm swearing off home paint jobs. I just don't have the patience to let them dry overnight like I should.

Second misadventure, I put it all together, tested voltages at my bench, all looked good, so I buttoned it up and put the screws in.
I went an plugged it into my chain, bypass sound works great woohoo, first hurdle. I turned it on.....no sound. I was like wtf?
I can understand borking a complicated modulation pedal but borking a YATS? How the F could I mess up something so simple?
Anyway, back to bench, screws taken out. I could hear @Chuck D. Bones voice....."Have you done a thorough inspection?" heh.
Well first thing I checked was to make sure the opamp was oriented correctly. When I looked at it........it was an LF351, not an LF353.
Somehow my baggies of 351's and 353's got mixed up. I had some of each in both bags. I can't remember when I bought these but obviously I was spacing out when I was putting them away.

So easy fix, popped in a 353 and all is well. According to Aion, some of the later run of these used TLC272's. Apparently Juhl wasn't happy with how the 353 sounded on battery as the voltage dropped below 8v. The TLC272 sounds more consistent across the life of the battery, however, he likes the 353 sound better, so if you're never going to use a battery (like me) then the 353 is the opamp he would choose. Early editions of this pedal came with both opamps for users to swap as they needed.

Next couple of BJFe projects I have queued up is the "Simble" (PPCB Symbolic Drive), which is Bjorn's take on the Zen drive. It seems to me that the Zen is all about the smoothness and almost diametrically opposed philosophically from his own designs. I'm super curious how that's going to sound. I'm missing the opamps for that (TLC272 ironically:) and my Mouser order was uncharacteristically slow in getting fulfilled. But it should be here next week sometime.
And also the Graphite Drive (Mad Prof Stone Grey Distortion).

I also sent my demo video of the BJuhls pedals to my buddy who immediately responded "I would like one each of the last two on the left please..." heh.
So I'm building him a Mojito Deluxe and an ADHD Ge.

After that, I'm planning to build some of the Juhl's fuzzes, the Apple Fritter and Fuschia, and I think there's one more BearfootFX distortion that's in the PPCB catalog.

IMG_4226.JPG


***Note I took the gut shot with the wrong opamp in it......

IMG_4225.JPG
 
Next couple of BJFe projects I have queued up is the "Simble" (PPCB Symbolic Drive), which is Bjorn's take on the Zen drive.

I just found out from @harmaes in a thread he found on FSB that the Simble (Mad Prof Symbolic Drive) is actually not a Bjorn Juhl design. He had nothing to do with it. It was designed by Finnish circuit designer Lassi Ukkonen. There appears to have been some trademark issues with "Mad Professor" marketing this pedal and I'm assuming this is why it was discontinued. (Because Bjorn Juhl is known as the "Mad Professor")

Ah well, now I'm not so sure what to do with this board. I really don't need another Zen derivative. Might try building it with an LF353 just for something different.
 
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I like this systematic approach — build all the Juhl pedals.

I, too, liked the two pedals at the far left in the vid just a hair more than the other pedals in the vid that I also liked.
What was not to like? Juhl love everything, build them all!




You're on a roll! Awesome build!
He's never been off a roll since he started building!
 
I was just about to post about the Simble not being a BJF design but you already got there! The Simble is very much a Zendrive, only with a few added parts which I think detract from the sound rather than add anything.

A few years ago I modded a LGW by separating the bass and treble aspects of the tone control and then changing a few other bits (as you do) and ended up with a quite different but very cool pedal I called the Gringo.
 
I was just about to post about the Simble not being a BJF design but you already got there! The Simble is very much a Zendrive, only with a few added parts which I think detract from the sound rather than add anything.

A few years ago I modded a LGW by separating the bass and treble aspects of the tone control and then changing a few other bits (as you do) and ended up with a quite different but very cool pedal I called the Gringo.
Yah I noticed he reversed the way the clippers work? Kinda wierd. And dropped the Ge diodes. Oh well, I already have the board, I may try some mods with it and see what I end up with. My favorite Zen drive isn't a Zen:) but rather the PPCB Tater Tot (Barber Burn Unit Small Fry) and of course the Grover.
 
And the beat goes on.....latest in my Bjorn Juhl deep dive.

This is Bjorn's take on a Tube Screamer. I was really curious what he would do to this circuit.
Well, let me start by saying.......it's still a YATS..... :ROFLMAO:. I'm not sure if the Mad Professor version (Green Wonder) made it less "YATSY"
but there's no doubt this version has the familiar mid range hump and "closed-ness" of a TS808.

Having said that, there's also some hallmark BJFE elements, first of all, as an opamp drive, his choice of an LF353 makes a pretty big difference in how the gain structure sounds. There's the unmistakable "chewy" aggressive "angular" gain. (As opposed to smooth and symmetrical) Also the tone control is called "Body" and it's pretty wierd how it works. It's like from CCW to noon it acts like a Timmy-Zen bass control then from Noon to CW it acts more like a treble control.

It's made even wierder because I did not have an A100k dual gang and substituted a C100k Dual. But it works fine, all the tones are in there albeit the taper is a bit off. Actually, I rather like the C100k here as opposed to the A100k. (The original pedal uses a B20k Dual Gang but these are hard to source so Aion made provisions to use the easier to source 100k dual pots).

My initial impressions when I plugged it in was a little bit of a let down. Not sure what I was expecting, but the more I play with it, the more I'm starting to dig it.
It does all the usual TS stuff, like rolling off the gain and rolling up the volume it can push an amp or other gain pedal well.
But turn up the gain and it "sounds" like you're kicking in some clippers but there's no toggle. Just a pair of green leds in the circuit. It can get pretty aggressively gainy all on its own.

I'd love to see @Robert do a project on the Mad Prof version of the Green Wonder.

So a couple of misadventures in this build, I didn't have a green enclosure so I used a bare enclosure and painted it with my duck boat camo green paint.
It came out perfect and felt dry. By the time I had finished assembling, I realized the paint was still soft and I had scuffed it up....sigh.....I'm down to two more bare enclosures then I'm swearing off home paint jobs. I just don't have the patience to let them dry overnight like I should.

Second misadventure, I put it all together, tested voltages at my bench, all looked good, so I buttoned it up and put the screws in.
I went an plugged it into my chain, bypass sound works great woohoo, first hurdle. I turned it on.....no sound. I was like wtf?
I can understand borking a complicated modulation pedal but borking a YATS? How the F could I mess up something so simple?
Anyway, back to bench, screws taken out. I could hear @Chuck D. Bones voice....."Have you done a thorough inspection?" heh.
Well first thing I checked was to make sure the opamp was oriented correctly. When I looked at it........it was an LF351, not an LF353.
Somehow my baggies of 351's and 353's got mixed up. I had some of each in both bags. I can't remember when I bought these but obviously I was spacing out when I was putting them away.

So easy fix, popped in a 353 and all is well. According to Aion, some of the later run of these used TLC272's. Apparently Juhl wasn't happy with how the 353 sounded on battery as the voltage dropped below 8v. The TLC272 sounds more consistent across the life of the battery, however, he likes the 353 sound better, so if you're never going to use a battery (like me) then the 353 is the opamp he would choose. Early editions of this pedal came with both opamps for users to swap as they needed.

Next couple of BJFe projects I have queued up is the "Simble" (PPCB Symbolic Drive), which is Bjorn's take on the Zen drive. It seems to me that the Zen is all about the smoothness and almost diametrically opposed philosophically from his own designs. I'm super curious how that's going to sound. I'm missing the opamps for that (TLC272 ironically:) and my Mouser order was uncharacteristically slow in getting fulfilled. But it should be here next week sometime.
And also the Graphite Drive (Mad Prof Stone Grey Distortion).

I also sent my demo video of the BJuhls pedals to my buddy who immediately responded "I would like one each of the last two on the left please..." heh.
So I'm building him a Mojito Deluxe and an ADHD Ge.

After that, I'm planning to build some of the Juhl's fuzzes, the Apple Fritter and Fuschia, and I think there's one more BearfootFX distortion that's in the PPCB catalog.

View attachment 41233


***Note I took the gut shot with the wrong opamp in it......

View attachment 41234
I can't understand how Aion thinks this is acceptable practice to design boards with half the Leg pads missing.
Don't get me started on the Footswitch PCB!
 
Yah, I tend to avoid Aion boards anymore. The only project there that really interests me at the moment is the BlueShift but not sure I want to tackle such a beast of a build in snippets between work meetings heh.
 
i was just reading through an aion document, and then i saw something that reminded me of your comment

View attachment 45887

what you reckon? is this BS or legit?

Well!, Everybody else must be doing it WRONG coz he is the only one doing it!!!
I trust Kevin's design abilities implicitly. His projects are well-laid out and feature plenty of firsthand research + mod tips.

Looking at @MichaelW 's gut shot photo, he's right. Dual gang pots are taller as a function of their design, so if the pot were to be under the board (or if the pads a little further down for a fully circular solder pad) the PCB would have to be elevated somewhat to create clearance between the dual gang and the bottom of the PCB. This is because the casing is flush with the bottom of the pins, and there are exposed parts beneath that cannot sit on the PCB directly- in the same way a standard pot cannot without one of those cover-things. If you were to push the pins into the PCB all the way, the pot would be angled upward out of necessity.

Is it a big deal? Obviously not. There are many PedalPCB designs with dual gangs that sit fully under the PCB- you just have to float the pots. (eg., On the Low Tide I just finished, many of the standard pots are floating out of necessity because of the dual gang's height.)
 
you just have to float the pots.

I generally don't do it myself, but we really should be floating pots anyway... More distance between the PCB and pots means less chance of noise, parasitic oscillation, etc ... (and no need for an insulator!)

I've rarely seen dust caps, pot condoms, or any form of insulator in a mass-produced pedal. Toggle switches also set the PCB height slightly higher than a standard 16mm pot unless you remove the inner nut.

Leveling the PCB is a minor one time inconvenience.... a wonky control layout is forever. :ROFLMAO:

As far as the castellated dual-gang pot pads are concerned, they're cool and everything, but it forces you to put all of your dual gang pots along the edge of the PCB (unless you do something crazy like a big cutout in the middle of the board). That sort of constraint doesn't always lend itself to the most logical control layout.

This also forces you to route the traces from the individual gangs on top of each other. Probably not an issue 99% of the time, especially considering how a dual potentiometer is constructed, but sometimes the more optimal path of exit is upwards away from the upper gang, not down between the lugs of the lower gang.

1681237454716.png

Like any layout technique, it's a good trick to have in your arsenal, but not something I would personally use regularly.

*This is, of course, entirely my opinion and should be taken with a grain of salt... I apparently like to unnecessarily route caps to ground as well.
 
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