Saturday, 21 April 2012

Dunlop - Eric Johnson Signature Fuzz Face EJF1

There is an ongoing discussion on FSB about this pedal, because we know that there are some hidden surface mount components underneath the board, and so this is based on a best guess by Marc Ahlfs after some experimentation he did on the circuit.

Info from Dunlop about the original:

No one cares more about tone than Eric Johnson, and his choice for getting sweet, singing lead tones is the Eric Johnson Signature Fuzz Face. EJ worked closely with Fuzz Face guru Jeorge Tripps to create his signature pedal. It is inspired by EJ’s prized personal Fuzz Faces and is built to his incredibly strict specifications, featuring hand-selected BC183 silicon transistors (for higher gain), custom repro ’68-’69 knobs, and a vintage-style hammertone finish. The result: a beautifully dynamic, expressive, and powerful pedal. “I first heard the Fuzz Face when I was about 12 and loved playing through it,” he says. “It’s the classic tone used by Jimi Hendrix, one of my greatest influences. No other pedal gets this type of sound. It’s the pinnacle of psychedelic fuzz.”






51 comments:

  1. could I use the BC184's on this?

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  2. You could use any NPN bipolar junction transistor like 2N3904, 2N5088, BC5089, 2N2222(A), BC108, BC109... Socket and try what you like best.

    BC184s are just higher gain versions of BC183s. Last character (L and C in this case) usually indicate the gain range within the specs. Check the datasheet:
    http://www.datasheetcatalog.org/datasheet/motorola/BC182B.pdf
    +m

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  3. mirosol, you give this one a go yet?

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  4. Built this last night with 2sc1815's for the pinouts , and can verify the layout. Although something's wrong because it doesn't make me sound like Eric!.

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    1. Did you check the gain of the 2SC1815s? The ones I've got a between 150 and 200hfe and so would be too low gain, particularly for Q2.

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  5. I've never used those little holes on the DMM before, could never get a reading, seems I needed to push the legs right in, great !! The 2sc1815's were about 290. Went through some and found a 2n3904 @ 164 and a 2n5088 @659. (with the legs twisted).Got the trim to 3.1v (used a 10k so a bit fiddly). Definitely has that nicer honk to the sound now. Thanks Mark.

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  6. Tried a bc550@278 in q1, think maybe better. Sounds much richer with the tone control wound off on the guitar, almost like it's working backwards? Is that normal for a fuzz face?

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  7. little confused here but i dont claim to know what i'm talking about when it comes to this stuff, but isnt the min hfe of a bc183L 120? why wouldn't they just choose an npn that had a normal hfe of 250 or is there more to it than that. just brought up this site for similar transistors to the 183's. might help people.
    http://alltransistors.com/crsearch.php?mat=Si&struct=npn&pc=0.3&ucb=45V&uce=30V&ueb=5V&ic=0.2&tj=150%C2%B0C&ft=150MHz&cc=5&hfe=120MIN&mnf=&caps=TO92

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  8. I've been experimenting a lot with trannies in this circuit and so far I really love a lower gain one with 2x 2n2396, with a resistor of 4,7k to be able to bias the Q2C at 4,4-4,5 volts. Great warm sounding fuzz IMO. Try it out and lemme know if you like it. ;-)

    I also combined a BC183C in Q1 (585 HFE) with anything around 300 HFE in Q1 (BC547-BC548-BC549B). Also with a 2n2222A in Q1 (HFE 200ish) it does sound great with 3v on Q2C.
    And finally a fuzz with 2x BC109C with 3v on the Q2C has the most gain and is also nice.

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    Replies
    1. That's a BC183C in Q2 of course. ;-)

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  9. Made using bc184lc from tayda. Works like a charm. Replaced 332R with 470R and put a 39nf in parallel to smooth out some highs. Now it sounds super smooth, creamy.......thanks harald for another great layout. But can you add another layout for a EBC transistor arrangement so that we can experiment more. :)

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    1. I'm Mark, Harald is the other guy! :o)

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  10. ha ha .....sorry mark....I know that.... actually before making the above post I was going through all the fuzz circuits in harald's website.....so it came out as a mistake :)

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  11. Sorry, bias q2 collector to 3v with respect to what ? . 9v line , ov or base ? Sorry if it seems such a dum question . Biasing is confusing the hell out of me at the moment ! If I measure bettween collector and base I can set 3v . However measuring bettween collector and 9v line I always get aprox 1v . The effect does appear to work though .

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    1. Whenever a voltage measurement is mentioned on the site, it is always between the point mentioned and ground unless otherwise stated.

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  12. Unfortunately I have background noise/wine . Altering gain makes no difference to the noise level. I've gone over the board several times and it looks fine .

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    1. Post a front and back pic of the board and we'll see if we can see anything. It may look fine but something is definitely amiss, whether that be an unintentional bridge, poor solder joint or faulty components, they're all things you are going to have to check for.

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  13. Ok , cheers mate , I'll do that a.s.a.p . Damn this site is good ! . I'm using transistor sockets so I think I'll target them first though .

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  14. Can't seem to post pic from iPad . In meantime I built the mk3 tonebender with ac125's which is amazing .completely started this one again from scratch but still can't get rid of what sounds like RF

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  15. There are 7 cuts not 6 as stated . I took it this was a typo ? Anything I could try to cut down the RF ? It biases to 3v fine and sounds amazing...accept for the RF . thanks as usual for a great site .

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  16. Built it again from scratch and still,the same . I think I'll,give up and build the fulltone 70 ! Thanks anyway guys .

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  17. Any chance of a "non-axial caps" version of this layout? :)

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    1. That'd be nice, I'd like one as well...?

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    2. The original TI BC183 from fee-bays lynnt850 are old school and sound awesome.
      No two had the same hfe, most were 200-250, some were as high as 350-450.

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  18. Just built one of these too and I've got nothing when you turn the effect on. I've even gone to simple no-LED switch wiring to try and find out why and it's still not working.

    http://i38.photobucket.com/albums/e116/xero_uk/Mobile%20Uploads/20140528_125139_zpsafjgnitj.jpg

    http://i38.photobucket.com/albums/e116/xero_uk/Mobile%20Uploads/20140528_125240_zpslqynxnqm.jpg

    Can any spot anything?

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    1. The cuts and component positioning looks ok as far as I can tell from the soldering, so can't spot anything obvious there. You'll need to measure the transistor voltages to see what that tells us.

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    2. Q1 C 2.5mv
      B *
      E 0

      Q2 C 0
      B *
      E *

      * means a weird thing was happening. The voltage was just climbing. Started at basically 0 and went up past 2v when I stopped measuring it.

      Just noticed btw that the diagram above says for the trannys B, C, E in the order. *Really stupid question alert* Should I have bent the legs on my transistors to match this cause afaik (and I do not claim to be an expert at this) normally they would be C B E, right?

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    3. If your transistors are CBE then yes the collector and base will need twisting over with some insulation or something in between so they don't touch. My BC183s are BCE pinouts which is why I used that order.

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    4. Ah. That'll maybe explain it! Teach me for not looking at the diagrams closely enough.

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    5. I've added a compact version with a CBE pinout so anyone with that configuration can build it without having to twist pins.

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  19. I'm so sorry but still struggling with this. I'm still on the original layout, but now I've swapped out the 2 transistors and changed the pins around. Just gone at it with my multi meter. Here's what I'm getting now.

    Q1 B - 5.35v
    Q1 C - 6v
    Q1 E - 0v

    Q2 B - 5.35v
    Q2 C - 6.5v
    Q2 E - 22 - 27mv

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    1. When you turn the trimmer is the voltage on Q2 collector changing?

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    2. Yes. The 2 extremes are 6.73v and 6.5v

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    3. That's not much of a change, certainly not as much as I'd expect. I think first thing first we need to make sure that we know exactly what the pinout is of your transistors or we're guessing and adding another potential cause of fault before we even start. Where did you get them from? Are you still not getting anything out of it at all?

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    4. Bought them from mouser. I'm using 2n3904 for Q1 and a 2n5088 for Q2. Could this be the issue? I had to get what I could find. Couldn't get BC183 anywhere so settled for these.

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    5. And yes, when I click the effect on, nothing.

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    6. Right so based on those transistors, if you rotate them 180 degrees so the flat side is to the right, the pinout is:

      C
      B
      E

      So do that and then twist over the collector and base to give you the required:

      B
      C
      E

      Make sure the twisted pins don't touch.

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    7. Yep, definitely how I have it.

      https://www.dropbox.com/s/nwgidn7wgogv1ou/2014-05-31%2014.25.16.jpg

      And they definitely aren't touching. Just treble checked it with the continuity checker on my meter.

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    8. Got this one done...
      when I dime the fuzz knob it has a screech to it... oscillating I guess... will increasing that 27p cap to something bigger help that out? I may end up rewiring it too however... nails the Fuzz sound of EJ fuzz.. rubbery! I have a BC183 hFE about 240 for Q1 and a BC183C hFE 501 for Q2... lovin it! just cannot dime the fuzz all the way :-(

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    9. Did you build the newer compact layout?

      You could try increasing that cap size, or possibly increasing the 27R resistor. But have you boxed it yet? The shielding of the box may remove a lot of the noise and so you may not have to tweak as far as you suspect. I always gets lots of oscillation with silicon Fuzz Faces which is tamed a lot when boxed.

      I'd suggest socketing the 27p and 27R and then experimenting when you've got it in a box if required.

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    10. I have it boxed but the back was off. I am using the 1st layout but yeah... I am using a crappy used enclosure that is not drilled properly so I have long wires everywhere so I will box it up in a properly drilled enclosure, and also socket 27p and 27R and test it out. I am actually thinking about putting it inside a 1590BB with an Octavia build because they go together like um... Cream n Coffee LOL

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    11. baaa.. I put the back on the enclosure and it still oscillates. I did not have a C470k pot handy so was using a A500k as well...
      Going to try swapping out the 27p and 27R with other values and also tying some other transistors in Q2 before I get drastic and tear it down! LOL

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  20. I got this where I want it...
    I put a BC183C with hFE of 540 into Q2, 39pf cap... Man tell you what, this pedal is great into a cranked plexi, amazing! thanks IvIark!

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  21. Oh another side note... not sure what is up but I also like the volume pot value A100k instead of 500k... brings out the highs and not so farty! that is all! hehehe

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    1. I had the same problem as you - mine oscillates with the gain cranked, so I have to back it off to 4:00 to get rid of the (bad) noise. I'll try changing that cap.

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  22. Hey Mark, I found some BC183LC transistors. Are these different from the BC183Ls? I will measure them, but want to know, if I could use them.

    Thank you! ;)

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  23. This comment has been removed by the author.

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  24. Troubleshooting report for those who are having issues with oscillation and radio frequencies:

    Firstly, I took some time to read other people had to say on forums like FSB and I decided to try some of the methods mentioned by them to address those issues. One of them was adding a 1K resistor in series with the input - totally cured the RF problem with guitar volume on "0".

    Second issue: the oscillation at 4-5:00 on the gain pot was still there (no matter how many transistors I tried). I noticed the (bad) noise would be gone when I turned my guitar's tone controls to 3 or 2, leaving only that loud, syrupy fuzz that still had plenty of cut, so that indicated to me I could try increasing the value of the 27pf capacitor (since a small cap in parallel to a transistor's B & C is an easy and traditional way of defeating harsh high end and noise on a fuzz face) and upping that cap to 100pf was the solution.

    This little mod leaves you with all the good high end, there's no compromise to tone at all. If you have a darker sounding guitar than mine (I have a Strat and a Tele) a smaller cap value would probably be enough. Experiment with it.

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  25. Replies
    1. You could try higher hfe transistors and/or a higher value resistor in place of that 330R (common mod for fuzz faces). Try 470R or even 1K.

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