Mojo Hand Iron Bell

[Liustucru]

Hello,
I've found a video of the new Mojo Hand FX fuzz pedal and I have to admit that I was very impressed by the sound and versatility of this fuzz.

Here's the video:

I have questions for Muff experts:
What kind of Muff the Iron Bell is ?
Is the colour control knob identical to mid knob on the mudbunny board ?

I didn't find any schematics.
What I like about this pedal is it can be either warm or crispy and it sounds very good at low gain settings where most muff variants are muddy and undefined.

I'm interested in any additional information you could find.
Maybe it will be another column to add to Juansolo's Muffs.xls database and mudbunny project doc.

[jubal81]

Older thread, but I have the same curiosity.

[midwayfair]

CultureJam posted a schematic and board somewhere, probably BYOC.

[jubal81]

Thanks for the heads up. Found the Spasm Chasm thread at BYOC.

[croquet hoop]

I have been searching for info on this pedal as well, and in addition to the aforementioned Spasm Chasm project by culturejam there is also a vero layout available at tagboardeffects. Unfortunately no schematic is provided, so I traced back the vero layout and reported the values on a Mudbunny schematic for the sake of clarity:



Adjustements were minimal since everything corresponds to the schematic, safe for a few things:

– the power section of the Mudbunny is more elaborate, so I kept it as-is (C14 is 100u, C15 is 100n)
– C4 and R8 were switched on the vero layout (lug 2 of sus pot -> R8 -> C4 -> base of Q2); I left them as on the Mudbunny schematic, I have no idea if this is an error or a design choice. You might want to experiment.
– the Iron Bell has a fourth pot labelled "Colour" ("Contour" in culturejam's schematic; the name is different, the implementation is identical); it is not the same as the usual "mid" pot (which comes after R18, whereas the Colour mod is in parallel to C10).
– according to culturejam, there are also treble bleed caps on the sus and vol pots, but I don't know their values.

That's it for the schematic. So you can build the IB on a Mudbunny board if you wire the extra pot off board, or you can use one of CultureJam's, which has the extra knob wired right. And board mounted pots too!

As for the values, I compared them to the ones found in Juansolo's spreadsheet, and it appears that the IB is strikingly close to the P19:



(Spasm Chasm values re-labeled to fit the Mudbunny template; values absent to either build but common to every Mudbunny variant added, namely R1, R24, C15 and D5; CMod is C16 in the schematic).

The main differences are the choice of transistors (as usual, socket and experiment) and the 330n cap, which is absent from the Spasm Chasm while at least one can be seen on the IBell pcb (along with maybe a 220n):



(picture taken from tgp)

Once again you might want to socket C12 (330n in the P19) and C13 (330n in the vero IB) and experiment.

That's about it for this pedal. I don't have everything I need at the moment but I'll surely try to build one. If anyone does, make sure to report on the forum!

Just two last things:

– I am not sure whether this kind of message (basically explainig how to reproduce a recently introduced boutique pedal, be it based on a 40 year-old schematic and using almost the same values from another boutique pedal...) is in step with the rules/ethics of the forum. If it is not, feel free to delete it.

– if it is, since we're past the "request" stage, maybe we can move it to the "member's projects" section?

[juansolo]

Missed this... Will add to the spreadsheet shortly

[croquet hoop]

The Tagboard version and CultureJam's Spasm Chasm have slightly different values, which one are you going to add? 

I got a few boards from him and just populated one with the values he provided (so it's not exactly an Iron Bell clone), I'll probably make the other one as well to compare (but apart from C13, I don't think the differences are significant, so maybe just socketing this cap will do).

Edit : I just reviewed the schematics, and the differences are (Spasm Chasm value first, then Iron Bell):
- R1: 33k instead of 30k
- R3: 100R instead of 120R
- R6: 1k instead of 820R
- C3: 68n instead of 56n
- C13: 100n instead of 330n

Also, the BOM he provides indicates 470p for C2, C5 and C8, but the schematic in the same doc shows 560p caps.

[juansolo]

Easy enough to post both there. The Ultrastoner is only a couple of changes and a mid pot from a Skreddy ?Lady and that's on there

[juansolo]

K, they're added. I've had a bit of a re-shuffle (to put related things near each other) and added some other rows (pots weren't on there, they are now). I've also had a go at making it a little easier to read... Hopefully that works out.