# Bellum Fuzz MKI parts values



## manfesto (Jan 19, 2021)

Was looking at the documentation on the FuzzDog RawFuzz V1 and see that they have two BoMs



			http://pedalparts.co.uk/docs/RawFuzz-V1.pdf
		


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The original DBA circuit apparently uses 2N5089s (probably pre-sorted for low gain?), 430K biasing resistors, and 680nF caps in every stage, which apparently very rarely works the first time.

FuzzDog's "stable" circuit uses 2N5088s, 820K biasing resistors, and 220nF caps in every stage.

@PedalPCB's Bellum on seems to be 2N5089s, 430K biasing resistors, and 100nF caps in every stage.

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I know PedalPCB likes to say they "don't make the weather, just report on it", so I guess I'm wondering

A) who has the original trace correct? FuzzDog with the 680nF caps, or PedalPCB with the 100nF caps?

B) would it be smart to build the Bellum MKI with FuzzDog's "stable" BoM? Or is this circuit not actually as touchy as they're making it out to be? (yes yes I know the right answer is "just socket everything and try" but still)


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## Betty Wont (Jan 19, 2021)

I don't know what is right, but I have my experiences. I have built both fuzzdog versions (on their boards) and the "stable" version works fine every time. I could not get a viable fuzz sound out of the 2n5089 version with unsorted gains. Either too gated to pass signal or squeals on wheels.


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## manfesto (Jan 19, 2021)

Torgoslayer said:


> I don't know what is right, but I have my experiences. I have built both fuzzdog versions (on their boards) and the "stable" version works fine every time. I could not get a viable fuzz sound out of the 2n5089 version with unsorted gains. Either too gated to pass signal or squeals on wheels.


Did you try building with 680n caps? If so, was it indeed too crazy?


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## Betty Wont (Jan 20, 2021)

manfesto said:


> Did you try building with 680n caps? If so, was it indeed too crazy?


Yes, with 680n caps and the 430k bias resistors it was uncontrollable noise. I haven't tried 5089 & 100n caps.


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## Robert (Jan 20, 2021)

The preview image was outdated, the PCB has been revised since then.  (I've also just updated the preview to avoid confusion)

This circuit is a complete mess.....

2N5089, 430K, and 100nF is what was used in an original.     The circuit will almost certainly _not_ work with these values.    I say "an original" because there are apparently multiple versions going around with different values.    The PCB is marked for 680nF coupling caps, but 100nF capacitors were installed...

Normally yes, I go with the original circuit, flawed or not.    But in _this_ case you will not get the results you expect by following the original circuit, I could not in good faith leave the circuit broken just because "thats what was in the original"...

The PCB was redesigned to use 820K bias resistors with 680nF coupling caps.     You can feel free to experiment with any variation, but I suspect you won't be happy with 430K bias resistors.  All I got was a gated nasty mess.


I would _really_ like to get my hands on an original so I can measure the specs of the transistors, but the V1 is a bit hard to find.


If you happen to see a V1 for sale, or know someone who has one and might let us borrow it that would be great.


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## Mir9 (Jan 20, 2021)

I've also been waiting to get this one working. This is the only one I've seen traced on a forum years ago.  It has the 430k (yellow-orange-yellow) resistors and 100nfs though I've also heard of some having 680nf.




Besides the first half, where the fuzz is happening, the rest is confusing too.  There's the 680pf in the tone section where the silkscreen asks for a 4n7. Last minute change at the factory?  Then there's the missing 27k which would make the germanium clipping diodes useless.

I have a friend who told me he opened up a real one long ago that had a 4n7 tone, and no clipping  diodes on the last stage. No pics though.  Another guy on a forum was selling clones of one he claims to have traced  and told me his had a different value in that position, but never answered back with what.

I built a clone of  the DBA Soundwave Breakdown. The fuzz section is like the Fuzz War's but with  910k resistors. It's a very heavy sustain fuzz and not overly gated.  The different tone and bias controls get you more versatile sounds.
Others that use those reverse gain stages but with 910k instead of 430k are:   Interstellar Overdrive, Harmonic Transformer, and the Supersonic Fuzz Gun (though I had problems with that one gating too much)


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## manfesto (Jan 20, 2021)

Mir9 said:


> Then there's the missing 27k which would make the germanium clipping diodes useless.


I remember the original preview image for the Bellum Fuzz said "27K N/A" in that spot, and the new one says "*27K*" with similar markings for one of the diode pairs, I guess to say you can omit them depending on which of the (apparently NUMEROUS) versions of the Fuzz War V1 you want to build?

Also, looks like ceramic caps?


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## McClinticSphere (Jan 26, 2021)

In an attempt to understand the variables for this circuit a tiny bit better, I measured h_FE of 35 each of NOS (Motorola) 2N5088 and (GE) 2N5089 at 2.5 mA with a DCA55. The 2N5088s range from 538 to 639. The 2N5089s range from 510 to 839. The sample size isn't really big enough to establish meaningful statistics but mean of 2N5088 is 592, stdev 33, and 2N5089 mean is 667, stdev 85. So 7 randomly selected 2N5088s have a much bigger chance of representing the lower side of h_FE than 7 random 2N5089s.

I at least managed to get 7 of each with similar "low" gain values so will see what happens on a breadboard with the different resistor/cap combos.


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## manfesto (Jan 26, 2021)

McClinticSphere said:


> In an attempt to understand the variables for this circuit a tiny bit better, I measured h_FE of 35 each of NOS (Motorola) 2N5088 and (GE) 2N5089 at 2.5 mA with a DCA55. The 2N5088s range from 538 to 639. The 2N5089s range from 510 to 839. The sample size isn't really big enough to establish meaningful statistics but mean of 2N5088 is 592, stdev 33, and 2N5089 mean is 667, stdev 85. So 7 randomly selected 2N5088s have a much bigger chance of representing the lower side of h_FE than 7 random 2N5089s.
> 
> I at least managed to get 7 of each with similar "low" gain values so will see what happens on a breadboard with the different resistor/cap combos.


Wow, those are pretty hot transistors! My 2N5088s usually clock in around 250-300 and my 2N5089s are about 450-500.


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## McClinticSphere (Jan 29, 2021)

manfesto said:


> Wow, those are pretty hot transistors! My 2N5088s usually clock in around 250-300 and my 2N5089s are about 450-500.


I was kinda worried about this after seeing values elsewhere and seeing that the I_c dependence of the h_FE is not very strong, thanks for sharing. I ordered some more of each from different sources to compare.


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## Ratimus (Feb 4, 2021)

My guess is that there were all kinds of revisions done on the fly to the original units. Multiple cascaded changes due to hFE variations (particularly since they're in backwards), remove the shunt feedback diodes or not, all kinds of crazy stuff happening. With all due respect to the designer, he's known for being a seat of the pants experimentalist, not for making stable, consistently produceable designs. My gut says the originals probably all sounded different anyway, so personally I wouldn't chase nailing the exact authentic sound since I doubt there is one. I built one on perf a while ago FWIW, I think I used like 400nF caps, 830k resistors, and one or two of the transistors sounded better if they weren't backwards (blasphemy!)


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## McClinticSphere (Feb 4, 2021)

manfesto said:


> Wow, those are pretty hot transistors! My 2N5088s usually clock in around 250-300 and my 2N5089s are about 450-500.


I bought some more and it starts to become a bit clearer why the part number is not that helpful in choosing components for this circuit. These are the ranges of h_FE for 2N5088/9s from different sources (number of components in parens).

2N5088 (35) 538 - 659
2N5088 (10) 463 - 522
2N5088 (10) 528 - 574
2N5088 (20) 276 - 302

2N5089 (35) 510 - 839
2N5089 (25) 744 - 816
2N5089 (10) 498 - 554

So a set of 7 2N5089s from the 3rd source would be lower gain than a set of 7 2N5088s from the 1st source, but it you got 2N5089s from the 2nd source they'd be tightly distributed around an hFE of 773 which is really high and useless for purpose. The 4th set of 2N5088s is way lower.

My goal isn't really to make an original one, it's more to get some feel for why the higher value caps/resistors are necessary and how any of the originals could have had 2N5089s at all. I have run out of energy for buying more transistors though now that I have a ton I don't need. Time to move to a breadboard I guess.


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## Hexjibber (Feb 10, 2021)

McClinticSphere said:


> I bought some more and it starts to become a bit clearer why the part number is not that helpful in choosing components for this circuit. These are the ranges of h_FE for 2N5088/9s from different sources (number of components in parens).
> 
> 2N5088 (35) 538 - 659
> 2N5088 (10) 463 - 522
> ...


FWIW when I did my build of the V1 Fuzz War on the PCB Guitar Mania board, I found the transistors needed to be quite closely matched and in the range of around 350-370hFE. Unmatched sets didn't sound right, and higher gain sets (500 and above) just didn't work at all. I've done two builds using those boards now. Will be interested to know if thats the case with the Bellum as my build also uses 820k bias and 680nf coupling caps.

Did a demo video too if you're interested in what mine ended up sounding like;


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## Dan0h (Feb 10, 2021)

Hexjibber said:


> FWIW when I did my build of the V1 Fuzz War on the PCB Guitar Mania board, I found the transistors needed to be quite closely matched and in the range of around 350-370hFE. Unmatched sets didn't sound right, and higher gain sets (500 and above) just didn't work at all. I've done two builds using those boards now. Will be interested to know if thats the case with the Bellum as my build also uses 820k bias and 680nf coupling caps.
> 
> Did a demo video too if you're interested in what mine ended up sounding like;


Wow. I think that sounds awesome. I hesitated ordering one of these boards because the docs were not available and the complexity issues I’ve seen. But this sounds very tasty. Nice work.


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## Mir9 (Feb 10, 2021)

Though raising those resistors values helped me, it will also be worth trying some low gain MPSA06 & MPSA05's with the original resistors values.  Several people have advised me to try them on DBA clones, like mentioned here:

(On an FSB thread concerning the Fuzz Gun, which also used 2n5089's)
"reports that the current production units now use MPSA06G ... and a bunch of people reporting that changing the transistors in their clones makes them work as it should"  https://www.freestompboxes.org/viewtopic.php?f=7&t=12689&start=120


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## Mir9 (Feb 15, 2021)

Left is the back of the same board I posted above with the 680pf tone cap and missing 27k.
It was traced on FSB. https://freestompboxes.org/viewtopic.php?f=7&t=2692&hilit=fr

   The right is one I just saw on a TGP thread with an unusual red colored enclosure. The owner didn't post any pics of the top, but I noticed some differences. The second set of diodes and the 27k positions aren't present.
It also doesn't have the extrasocket ("add cap") for the other doubled up 120n+20n tone caps. 


			https://www.thegearpage.net/board/index.php?threads/strictly-fuzz.1271107/page-2150


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## manfesto (Feb 15, 2021)

Mir9 said:


> Left is the back of the same board I posted above with the 680pf tone cap and missing 27k.
> It was traced on FSB. https://freestompboxes.org/viewtopic.php?f=7&t=2692&hilit=fr
> 
> The right is one I just saw on a TGP thread with an unusual red colored enclosure. The owner didn't post any pics of the top,
> ...


So at some point they officially redesigned the PCB to drop the 27K and diodes, and also decided to stop cleaning their boards!


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## Robusto (Feb 24, 2021)

Hexjibber said:


> FWIW when I did my build of the V1 Fuzz War on the PCB Guitar Mania board, I found the transistors needed to be quite closely matched and in the range of around 350-370hFE. Unmatched sets didn't sound right, and higher gain sets (500 and above) just didn't work at all. I've done two builds using those boards now. Will be interested to know if thats the case with the Bellum as my build also uses 820k bias and 680nf coupling caps.
> 
> Did a demo video too if you're interested in what mine ended up sounding like;


I built PCB Guitar Manis version too. I could not get it to work as anything other than a high frequency tone generator. Now here I am in the middle of building this one and I’m...concerned. LOL


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## jonitto (Mar 16, 2021)

Robert said:


> The preview image was outdated, the PCB has been revised since then.  (I've also just updated the preview to avoid confusion)
> 
> This circuit is a complete mess.....
> 
> ...


As far as the "GE" germanium diodes with no value in the build for the MK 1, is there a more specific value for these?  Thanks


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## Bobbyd67 (Mar 16, 2021)

XD finished my build last night using the silkscreen values.... As expected it's a farty mess . Didn't have the time to troubleshoot but I know that manfesto made build report recently and he used 100nf caps on all the 680n ones and he seems to like it . In my end I think that swapping the 2n5089 for 2n5088 will help but haven't tried yet ! I am also tempted to try some 2n3903 since I ordered a bunch for the blackash recently ^^


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## Barry (Mar 16, 2021)

jonitto said:


> As far as the "GE" germanium diodes with no value in the build for the MK 1, is there a more specific value for these?  Thanks


I'd suggest sockets and try a variety


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## manfesto (Mar 16, 2021)

jonitto said:


> As far as the "GE" germanium diodes with no value in the build for the MK 1, is there a more specific value for these?  Thanks


You can use pretty much any germanium diode, they all clock in with a forward voltage of around 0.3V. I used D9Ks.


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## manfesto (Mar 16, 2021)

Bobbyd67 said:


> XD finished my build last night using the silkscreen values.... As expected it's a farty mess . Didn't have the time to troubleshoot but I know that manfesto made build report recently and he used 100nf caps on all the 680n ones and he seems to like it . In my end I think that swapping the 2n5089 for 2n5088 will help but haven't tried yet ! I am also tempted to try some 2n3903 since I ordered a bunch for the blackash recently ^^


I went with 100nF everywhere because the gut shot @Mir9 posted shows that at least *one* production Fuzz War went out with 100nFs in it lol

if you check the build docs for the FuzzDog Fuzz Raw V1, their “stable” BoM is all 220nFs, but they suggest all 470nFs if you want more bass (but recommend against it) or all 100nFs if you want it a bit tighter. Might build another with 220nFs at some point, but even with 100nFs I didn’t find the bass lacking.


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## dajones191 (Mar 17, 2021)

I built mine with 2n5088s and 1n34as and it sounds perfect


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## mdc (Mar 17, 2021)

Just curious, has anyone ever tried to just get in touch with Oliver from DBA and ask him wtfrig was going on inside the mk1 fuzz wars? He seems like a chill punk and given that they don't make that pedal anymore it seems like he'd probably share some insight into the revision/troubleshooting/stabilization process they used to get the first few batches out the door.


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## jejackson5 (Aug 25, 2021)

Noob questions. Looking for 20n, 120n film capacitors and the 100u electrolytic capacitor, but I'm not finding those exact values anywhere. Do I just go with the next closest value up?


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## manfesto (Aug 25, 2021)

jejackson5 said:


> Noob questions. Looking for 20n, 120n film capacitors and the 100u electrolytic capacitor, but I'm not finding those exact values anywhere. Do I just go with the next closest value up?


The 120nF and 20nF caps are in parallel and add up to 140nF.

I used a 100nF and a 47nF instead to get 147nF which is close enough. You could also just use a 150nF in either spot and leave the other spot blank.


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## ThePrairieWitch (Nov 11, 2021)

I just built a mk1 straight from the instructions, and it seems to work, but I'm reasonably certain that my Gain knob is functioning more like a Bias knob, if that makes sense?


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## ThePrairieWitch (Nov 11, 2021)

I


jejackson5 said:


> Noob questions. Looking for 20n, 120n film capacitors and the 100u electrolytic capacitor, but I'm not finding those exact values anywhere. Do I just go with the next closest value up?


I used an 18n in that spot, and it seems to work. My cab is in a iso booth and I didn't hook up the mic, so I do t have a perfect idea of how it sounds, but after boxing, it's not nearly as noisy as it was unboxed. My gain knob is odd though. When it's cranked it gets kinda gatey which I wasn't expecting


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## Chuck D. Bones (Nov 11, 2021)

jejackson5 said:


> Noob questions. Looking for 20n, 120n film capacitors and the 100u electrolytic capacitor, but I'm not finding those exact values anywhere. Do I just go with the next closest value up?


Yeah, get within ±20% and you're fine.  These builders who parallel caps and connect resistors in series to get some crazy value just make me laugh.  Unless you're building a piece of precision equipment, it just doesn't matter.

100uF is one of the most common electrolytic cap values.  Check Mouser, Tayda, Electronic Goldmine...


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