Dunlop - JBF-3 Joe Bonamassa Fuzz Face  [schematic]

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Xplorer
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Post by Xplorer »

looking at he tycobrahe schematic : am i right if i say that for an "octaved" basic fuzz it's as simple as adding the doubling octave circuit ( with the transformer and the two diodes ) , just between the 0,01 uf cap and the 500k volume pot, on a simple fuzz circuit or am i wrong ? cause i think that the smooth and rich personality of the joe bonamassa's germanium fuzz is a good candidate as a base for an octavia, i wanna hear it. the fuzz alone, of a tycobrahe ( through the different videos on youtube of some clones ) is really a fuzz that i don't like ...

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Post by Seiche »

Seiche wrote:so i finished mine today. YAFF right? but i gave my other ge ff to my friend for his b-day and started to really miss it. I really like the two trimmers.

i went with a 1k instead of the 332 ohm resistor, because it didn't have enough volume imho (i like to have some extra volume just in case. i guess joe can get away with it using multiple amps and effects loops etc.). I ended up using 1T308Bs for both Q1 and Q2 (Hfe 86 and 91) because they have very low leakage (i guess b/c they are military spec?) and sound great. I also left out the 10ohm res.
So i tried it with the normal 500kA volume control and compared to the 100kA i had in there before (forgot to mention) it is much too dark. Basically the stock version of this circuit is almost unusable for me, don't get why Joe would like such a low volume and dark fuzz, not really "tuned for HBs" at all imho. Only advantage of a 500kA is a rangemaster after the fuzz works better, but that can be remedied with a higher input cap on the rangemaster anyway.

The stock JBF-3 is supposed to really "shine" (TGP speak) when boosting a cooking amp, which i didn't get the chance to try yet.
All in all the I like Axis Fuzz of FuzzCentral much better for what I want. Maybe I'm a silicon-guy, though :mrgreen:

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Post by Xplorer »

yeah, it can be dark. it depends of what settings you're using, in the chain.
a 100ka volume pot would change this according to you ?
probably a different cap value, maybe lower, would be fine ? anyway i have an echoplex ep3 preamp after the fuzz/octavia on my project, and it can add some boost, some clarity, some control on the overal gain and noises when the fuzz knob is cranked.

mine sounds a lot like this one :



the recording isn't good but the performance and what you can imagine through this is incredible, to me.
( but not as trebly as the studio version of are you experienced )

yes, i'd think of this fuzz like a bit dark, and that's what i was looking for. now, it's a bit the same as jeff beck's use of the treble knob completely turned to 0, but getting some higher frequencys back , with a cranked amp.

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Post by Seiche »

Xplorer wrote:yeah, it can be dark. it depends of what settings you're using, in the chain.
a 100ka volume pot would change this according to you ?
probably a different cap value, maybe lower, would be fine ?
yes the 100kA definitely changes that. gets rid of the overall darkness (which is kind of like a "blanket"). Apparently that is also the value that Eric Johnson prefers. I only heard about that trick in "the technology of the FF" and other online sources.

Different cap value maybe, but that might also thin out the sound?

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Post by Xplorer »

i'll try it. thanks. yeah, i don't know the tech of the FF article by heart yet :D
do you remember where you discovered that it's eric johnson's favourite value ? interesting.
i love his version :



does it sound more like this ?

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Post by Seiche »

Xplorer wrote:does it sound more like this ?
i can't watch the video because of my "local region" :(

I read about the 100kA here and here, and possibly somewhere else. Try googling "100kA eric johnson" :thumbsup .

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Post by Xplorer »

yes, since i've seen that on the tech of the FF article. i didn't know that and i'll try it, thanks.
i'm thinking of this : why not having a 100k pot and a switch for a 400k resistor or a 400 - 500k pot which would act as a clarity controler ? i mean : switching or blending the highs or darkness ? what do you think ?

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and ... something i don't understand, maybe it's a stupid question but i could perhaps endly discover what it means : why would that be different to have a pot that is a 100k resistor, compared to a 500k pot that is set at (1/5 up)
100k of resistance ? and when both are all the way up, it means that they have zero resistance on the output, whatever pot value they are when they're rolled down, right ? so how is it different ?

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Post by Seiche »

Xplorer wrote:and ... something i don't understand, maybe it's a stupid question but i could perhaps endly discover what it means : why would that be different to have a pot that is a 100k resistor, compared to a 500k pot that is set at (1/5 up)
100k of resistance ? and when both are all the way up, it means that they have zero resistance on the output, whatever pot value they are when they're rolled down, right ? so how is it different ?
it's because the pot forms a voltage divider like this:
Image
now if you put the values of a 500k pot, compared to a 100k pot set at the same setting (1/5 up, or 4/5 up) in this formula:
Image
you'll understand. :thumbsup

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Post by Xplorer »

very cool ! :thumbsup
learning everyday. now i can understand a bit better the 1k to 2k fuzz pot.

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Post by Xplorer »

it's because the pot forms a voltage divider like this:

now if you put the values of a 500k pot, compared to a 100k pot set at the same setting (1/5 up, or 4/5 up) in this formula:

you'll understand.
Actualy now, i start again to not understand where is the difference.
because with this formula, if we compare the 100k and the 500k at half way up for example ( with Vin = 9v ) :

Vout = 50/(50+50) x 9 = 4,5

Vout = 250/(250+250) x 9 = 4,5

so .. why is it different to have a 100k pot instead of a 500k ? :? :)

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Post by Bernardduur »

High pass filter
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Post by Seiche »

Bernardduur wrote:High pass filter
that's right. the voltage divider explained above is the reason why a smaller pot has the same volume on all settings. But the output cap forms a high pass filter with the volume pot.

Image

The higher R gets, the lower the cutoff frequency is, passing less high frequencies leading to a darker sound.

Image

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Post by Xplorer »

ok.
so the 0,01 uf is C , and acts on the high pass, into this phenomen, with the pot and the ground. but i'm not sure to understand how i can find back what is what in this schematic, compared to the previous one with the pot.

on this one, R is going at this point where C and Vout are connected, and at the other point, is it the ground ?

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Post by Xplorer »

i think, if i'm not wrong, that Z2 is the R that acts into the high pass filter, right ? in any case ? Z1 acts only on the voltage division here, and Z2 in both situations ?

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Post by Xplorer »

guys, thanks for this important lesson.

i tried with a 100k lin as i didn't have a log, and i replaced the 1k by a 2k pot for the fuzz.
indeed, it's a lot brighter.
bu there are still some things i like when it's a 500ka pot. so is it right if i still use the 100k pot as a volume, but if i add a pot wired as a variable 500k resistor, between the two lugs of the 100k that define Z 2 ? ( second lug and the ground lug )
so i would have both worlds, and i could adjust the frequencys, from the previous 500k volume with its darker tonal character, to the simple brighter 100k volume pot used in this version, when the 500k pot has zero resistance. is it right ?

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Post by Xplorer »

but yes, thinking of this, if for example with the 100k pot set on max for max volume, and the 500k "tone" pot set on max for a dark sound, Vout = ( 500/(500+0) )x 9 = 9v , and some darker frequencys.

now , with the 500k pot set on zero, and the 100k volume pot set on max volume i'd still have
Vout = ( 100/(100+0) ) x9 = 9v and some brighter frequencys.

but if i set the 500k pot at max, and the volume pot at half way, the 500k pot would have an efect on the voltage division : Vout = ( (500+50) / ((500+50)+50) ) x 9 = ( 550 / 600 ) x 9 = 8,25v, much over 4,5v though the "real" volume pot ( 100k ) is set at half way..

i wonder how to do to avoid the effect of the dark/bright 500k pot on the voltage division, the volume.

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Post by Xplorer »

or perhaps a dual 500k pot, working equaly on Z 1 and Z 2 ? i think it's the solution , right ?

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Post by Seiche »

be careful how ohms law works, parallel resistors don't add up, that's resistors in series.

how about a switchable resistor in parallel to the 500k, giving you about 100k when the switch is closed (like a 130k? correct me if I'm wrong). letting you switch back and forth from 100k to 500k.
Image

i know Analogman uses a 250kA pot for the Sunface, as an in-between-choice.

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Post by Xplorer »

yes, very nice tech site about pots. i'll read it.

yeah, i realise that i was wrong, as the 100k pot and the 500k pot wouldn't be synchronised when turning.
but this resistor in parrallel could perhaps be replaced by a pot instead of using a swith ? and it would be much more simple than my previous wrong idea !

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