Boutique Jordan Bosstone: KFA Fuzzly Bear  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
Carlos3350
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Post by Carlos3350 »

https://youtu.be/Y8pYztnTZMM

Great sound, obviously the circuit has been modded.
Image
Image
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Here's what KMA say:
"We refined the circuit to get an old school sound with a modern Twist. First of all we brought back the low end and added a bias control to explore new capabilities of the forgotten pedal. The essential SKIN/MEAT knob controls the bias of the circuit. You can dial in a sharp skinny fuzzy tone or a thick and meaty wall of furry.

Here's what I can figure out so far:
Q1 2N222 metal can
Four 1N4148 clipping diodes instead of two
One ceramic cap as in the original Bosstone
Four WIMA film caps instead of three as in the original Bosstone: bigger values for more bass, two blendable input caps ?
Five resistors as in the original Bosstone: plus one resistor for the indicator LEDs

I cannot recognize Q2, since I have only got the pictures, but not the device. It looks slightly flatter than the usual TO-92 shape. Almost like a ZETEX BS170P.

I am not sure either as to how the SKIN/MEAT works. Does this pot replace the emittor resistor of Q1 affecting the bias?
Or does the pot blend two input caps like in this example?
Image

Carlos3350
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Post by Carlos3350 »

These are not the schematics, of course! This is just an example of blendable input caps :wink:

johnk
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Post by johnk »

the PCB labels that pot as 'Sag' so i would think that it's a bias control.

Carlos3350
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Post by Carlos3350 »

i think the term "sag" might be deliberately misleading by the manufacturer. I can see two film caps, one smaller and one bigger, next to Q1. That might point in the direction of a blendable input cap.

Carlos3350
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Post by Carlos3350 »

The values of the resistors from top to bottom, at least this is what I can see:

18k (brown-gray-black-red-brown)
2k2 (red-red-black-brown-brown)
560k (green-blue-black-orange-brown)
150k (brown-green-black-orange-brown)
560k (red-red-black-brown-brown)
4k7 (yellow-purple-black-brown-brown)

I guess the two 560K, the 18k and the 150k resistors are for the Q1 gain stage, just like in the original Bosstone
Image

Since there is a 150K emittor resistor, it seems as if there is no variable bias at the emittor of Q1.

Carlos3350
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Post by Carlos3350 »

Since there is no second 18k resistor, the SAG control might be something like this:
Image

poiureza
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Post by poiureza »

I see a black X instead of the pictures

Edit : nevermind, they showed up after I posted lol

Carlos3350
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Post by Carlos3350 »

I guess the SKIN/MEAT control is a sag control, the addtional film cap is probably parallel to diodes to filter out excessive treble.
I can't account for the two additional resistor. the 2k2 could be the limiting resistor for the two status LEDs. But what about the 4k7? Probably in series with the sag control as mininum resistance at the Q2 collector?

So the Fuzzly Bear coud be very similar to this - minus the second 18k, the Q1 emittor resistor and the switch:
Image

Carlos3350
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Post by Carlos3350 »

I have reverse-engineered the KMA Fuzzly Bear:
https://1drv.ms/i/s!AqJggSO-P0dXhgj3f03N_rD6juss
It's basically a Jordan Bosstone with bigger input cap, sag control and four clipping diodes. I have marked the modifications in yellow.

Carlos3350
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Post by Carlos3350 »

Here's the schematics:
You do not have the required permissions to view the files attached to this post.

enpreuss
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Post by enpreuss »

Hey guys, Enrico from KMA Audio Machines - interesting to see our pedals getting retraced.

Carlos3350
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Post by Carlos3350 »

I never trace genuinely new designs like Slreddy's pedals. I rather buy these pedals.
But what KFA claim as "their" pedal is a modded Bosstone. Most mods have been posted here or at diystompboxes.com.

EmmG
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Post by EmmG »

Thanks for posting, I like the original and the changes look useful. To be fair, KFA's site shows it's a Bosstone with bass mods.

EmmG
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Post by EmmG »

Thanks, Carlos3350. I gave a layout a try:
Image

Audio clip:
https://soundcloud.com/user-562468024/a ... 2017-04-06

I built it before realizing the gain pot cuts all signal at minimum. If this bothers you, add a 1k resistor between Gain #1 and ground. You can fit it on the board by connecting to ground elsewhere and adding a standing resistor and another cut. You could also make the board one column bigger on the left and add a cut. I would leave the gain high and control with your guitar's volume though.

If you already have a Bosstone built, experiment with the larger caps and voltage starve. I've seen voltage starve as a popular mod on Bosstones, the Rockett WTF comes to mind.

enpreuss
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Post by enpreuss »

@Carlos3350
We never claimed, that the Fuzzly Bear is a highly new designed pedal, based on nothing. As you can see, and like EmmG already said, everything is mentioned on ou website, that the pedal is based on the Jordan Bosstone.

Even when the mods were posted here on diystompboxes.com, doesn't say we just copy and paste stuff. The fact that we say, that the Fuzzly Bear is "our" pedal is based on the fact, that we build the Fuzzly Bear. So I don't see any morally reprehensible issues here. Tell me when I am wrong, but I am convinced, that we telling no lies about our pedals to anyone.

BTW: The company is called KMA and not KFA ;).

jrfox92
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Post by jrfox92 »

enpreuss wrote: BTW: The company is called KMA and not KFA ;).
This was definitely driving me up the wall.

It's right there on the pedal, guy. :roll:

Carlos3350
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Post by Carlos3350 »

enpreuss wrote:@Carlos3350
We never claimed, that the Fuzzly Bear is a highly new designed pedal, based on nothing. As you can see, and like EmmG already said, everything is mentioned on ou website, that the pedal is based on the Jordan Bosstone.

Even when the mods were posted here on diystompboxes.com, doesn't say we just copy and paste stuff. The fact that we say, that the Fuzzly Bear is "our" pedal is based on the fact, that we build the Fuzzly Bear. So I don't see any morally reprehensible issues here. Tell me when I am wrong, but I am convinced, that we telling no lies about our pedals to anyone.

BTW: The company is called KMA and not KFA ;).
I'm sorry for misspelling your company. You're not telling lies about the pedals you clo ... err ... build.
Neither do I see any moral issues in reverse engineering just another version of the Jordan Bosstone.
Regards

bc108
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Post by bc108 »

Can I ask which is the 2nd transistor? the PNP one (to126?)

EmmG
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Post by EmmG »

Updated layout with minimum gain resistor and pics of my build:

Image
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bc108
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Post by bc108 »

Which is the result you get using 4 diodes?
More compression?

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