Saturday 21 March 2015

Catalinbread Sabbra Cadabra


Update, 22.3.2015 **There were couple minor issues with the schematic. Both fixed for this version of the layout.**


122 comments:

  1. Awesome!

    This one will get built immediately! Good to see you back

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  2. I'm so happy Tagboard Fx is back!!

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  3. what is a good alternative for MPF4393?

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    1. 2n4393 or 2n3972 thats what i found on internet. Here in brazil i can find the 2n4393, so i guess in another country is very easy to find.

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    2. PN4393 are widely available, but any N-channel JFET should work and sound close enough. J201, 2N5457, MPF102, etc.
      +m

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    3. Looks like a muamp so any common jfet should do. Watch the pinout though !

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  4. is there any one who can make a youtube video showing these things being put together and do the sound testing.. i don't have electronics store nearby

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    1. Stuart I suggest starting out with a kit from BYOC.com and getting your bearings with stuff there. After you've done that, maybe try one of the simpler schematics on this site.

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  6. Miro, lovely to see you back. Will have to give this one a go. Any good alternatives to BC184 that should work pretty much the same? I have loads of NPNs but no 184s. Would BC550c do the job.
    Thanks.

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    1. yeah this part of the schematic is basically like the naga viper treble boost. I built and tested it with 2n5088, 2n3904 and 2n2222. The 550 will do just fine I think. Watch the pinout though !

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    2. I think it could be OK, but a B should be better, seems to be more similar

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    3. Thanks guys. Might build this one next weekend as finishing off a few others today.

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  7. Wow, this was worth the wait. Nice layout. Great sounding demo, Andy makes me want to play without a pick.

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  8. Oops, I had already started this before I saw the corrections on fsb. The fix I did for the 1m isn't too bad though. Wish me luck

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  9. Been looking forward for this! Thank you!
    You think this will fit in a 1590B or should I order a BB?

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    1. After readint the Vero Layout Guide I think it should fit, since it's 21 columns. Looking forward to see pictures of your builds! :)

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    2. After readint the Vero Layout Guide I think it should fit, since it's 21 columns. Looking forward to see pictures of your builds! :)

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  10. Wow!
    Nice layout and this will be added to my to do list LOL
    I may take a stab at making a PCB as well.
    Glad to see this blog is still going too!

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  11. I'm trying to buy bc184 on eBay but I see several types listed, bc184l,lb, and bc184c. Anyone know what was in the original pedal? Thanks.

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    1. if i'm not mistaken bc184c are high gain bc184 and i believe had a the same pinout as well, while the bc184l and bc184lb have different collector currents according to the datasheets, and subsequently have a different pinout. you can use any of the above in the layout, just mind the pinout. i went looking on ebay, and found these

      http://www.ebay.com/itm/Transistor-BC184-NPN-TO-92-34-Pieces-/390428182358?pt=LH_DefaultDomain_0&hash=item5ae7554756

      if you're in the US it seems like a good deal, and you should get it quickly compared to getting it from china.

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  12. I finished my build tonight and it works! I used Mirosol's old layout (as I had built it already before the new layout was published) and made the corrections on the board, which were easy to do. Just a standup 1M resistor below the 10K in the Naga Viper and a connection of Output 3 to Presence 3.

    I used J202s for the JFETs (2N5457s work too) and an ordinary 2N2222 for the BJT. I also used a 500K linear pot for the Range control as I didn't have a reverse log (worked OK).

    It sounds great. The Range control works really well to bring the input from low gain trebly to higher gain with more bass. There's a lot of gain on tap from the mu amp stages, but it never gets gated or blatty. The Presence control also works well to control the tone. So all in all, a worthwhile build.

    If you want to experiment, you can control the overall gain and tone by playing around with the Naga Viper part of the circuit. For example, in the emitter leg, reducing the 47 uF cap to 22 uF and increasing the 47 ohm resistor to 470 ohms lowers the gain somewhat but retains the overall character of the sound.

    The only issue I had during testing was some hum/noise. This is a high gain build, so I expect the hum will be reduced when the board is boxed. I also noticed that the noise could be reduced by putting a buffered pedal in front (I used my Klon(e)). I'll check the board for possible cold solder joints or minor solder bridges.

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    1. Sweet! Glad to hear it is tagged!
      For the noise, I would use some shielding cable for the ins and outs, that should help out.
      Also this 3PDT daughter board could help out. I heard they are good for high gain circuits.
      https://oshpark.com/shared_projects/Buk2PeKO may be a nice

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    2. I recently spoke to someone that has the original and they said it is a noisy pedal, so noisy that they contacted Catalinbread who said that it is noisy due to the 'traditional way the treble booster is designed'

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    3. From my experiments, increasing the emitter resistor from 47 ohms to 470 ohms (like the CB Galileo) reduces noise but also the gain. It's not a bad option though as there is more than enough gain from the subsequent mu amp stages.

      I also noticed that the Naga Viper has a 1 nF cap from the input to ground, just before the Range control. I may check this out to see if it has a beneficial effect. Apart from that, putting a buffer at the inlet would probably reduce some of the noise and provide a much better input impedance for the guitar signal.

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    4. I believe Catalinbread has recently actually tried remedying this with see through hot glue! Check their Instagram account for photos

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    5. Frank, did you try anything with the range control? One thing I noticed is that all the workable range is at one end, so it seems like a linear pot would be better than log in this case. I really like the territory it covers (in terms of tone), though.

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    6. Also, mine is not noisy. Strangely enough, I rarely get noise as a problem on any pedal anymore. Must be doing something right.

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  13. You could increase the value of that 47pf cap between the base and collector of Q1 to reduce the noise. You'll have to experiment to find the best balance of noise and high frequency roll off

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  14. The MFP4393 trannys are available on Ebay at a reasonable price. Don't know anything about the seller. I did order some so I try to test them when they come in.
    http://www.ebay.com/itm/390880389776?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

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    1. I saw those but at $1.50 each I thought they were pretty overpriced. Tried to make an offer but the seller would only knock off 50¢

      The PN4393 that Miro suggested are available at a much cheaper price. Didn't read the datasheets to see if there are any differences though

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  15. SOT brother found here
    http://www.mouser.com/ProductDetail/ON-Semiconductor/MMBF4393LT1G/?qs=sGAEpiMZZMv4z0HnGdrLjnwNZ9rg4nWl11baa1eyKp4%3d

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    1. Thtat is the right piece and somewhat cheaper. I believe I have found a 3-hole substitute here: http://www.ebay.com/itm/50PCS-PN4393-Encapsulation-TO-92-SINGLE-N-CHANNEL-JFET-SWITCH-/131218121239?pt=LH_DefaultDomain_0&hash=item1e8d35a217

      According to this datasheet: http://www.datasheets360.com/part/detail/mpf4393/3848263618536507948

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    2. hmmm I think those Fairchilds would be perfect!
      Fairchilds version of the same fet I suspect

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  16. Leo - you mean the ones I posted $11.67 for 50 pieces. They looked good to me as well, especially after I found the datasheet I posted as the second link above. It has the PN4393 listed as a "featured alternate" of the MPF4393.

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    1. Motter,
      PN4393s @ 11.67 for 50 is a pretty good deal. Thanks for the heads up on those!
      :-)

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  17. Hi guys,

    Just for information: MFP4393 30 cents / piece in musikding:

    http://www.musikding.de/MPF4393_1?lang=eng

    Short supply now. I 'm sure that kalus is wondering why there's now such a higm demmand of this tranny :P

    J.

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    1. It's in short supply because I snatched up most of them. Muhahahahaha!!!!

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    2. *shakes fist angrily*

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  18. In fact - here is the store with all kinds of options including SOT or 10 pieces for $3.00

    http://stores.ebay.com/UTSOURCE-STORE/_i.html?_nkw=jfet+4393&submit=Search&_sid=1084113345

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  19. NIce find JaviCap, I was wondering about the same thing. (if they were wondering about the sudden demand). I should have been more clear - the SOT I found are MPF4393 (5 pieces for $2.50) while the 10 pieces for $3.00 (or 50 for $11) is for the PN4393

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  20. Hi,

    Just some notes on this effect, as it bothers me a little that these subpar engineered effects seem to get so much praise. The whole design is bugged from the start to the end.

    a) The "Naga Viper part" adds substantial distortion (may or may not be desired) with most pickups that are not "vintage"-output. More voltage and tasteful biasing will decrease noise and prevent the distortion

    b) The noise is directly an issue of the high impedance biasing of the mu-amp stages 2x(1M || 1M), the high impedance of the gain-circuit (around that pot) and the high impedance biasing of the source follower (2M2 || 2M2). Start reading R.G. Keen articles from centuries ago ...

    c) JFets profit from source resistors (read fetzer valve or even better the original Danyuk article) and higher voltages. 24Vdc ain't any problem with charge pumps.

    just my 2cents

    max

    PS: From my notes

    - 47R on Emitter oft he BC184 should be made larger than 47R – up to 560R
    47R is a Gain of more than 40 an clips already with 0.2Vptp input
    560R is a Gain of 15 and does not clip
    With 560R || 560R and 10µF/4µ7 and 18V the Gain is 27,5 with enough headroom

    Mu-Amps general:
    - Try imbalanced biasing with 4k7 – 10k Trimmer – 4k7
    - Try noiseless biasing (http://www.geofex.com/Article_Folders/modmuamp/modmuamp.htm)
    - Do not completely bypass the source of the bottom Jfets
    - Operate with 24Vdc
    - Gain circuit after first mu-amp can be made lower impedance by a factor of 10 -> lower noise
    - ToneStack with Trimmer for Treble, Bass, Middle
    - Biasing of the last stage (source follower with lower impedance! –noise again)

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    1. Good info Max.
      The guitar I will be most using for this pedal is an old 69 SG special with P90s so I should be good to go, except for the dreaded single coil hum but, that is ROCK N ROLL!
      hehee

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    3. I managed to try an original today in my local second hand gear shop. I personally didn't experience any excessive noise that I wouldn't expect. To be honest, if you're going to buy this pedal then you're obviously a Sabbath fan so I would imagine you'd already be using 'vintage' spec pickups. It seems daft that someone would buy this pedal and plug their pointy headed active EMG shred beast through it... and I echo what Leo said...noise? f**k it, it's rock n' roll.....

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    4. Got a lovely tone from my screamin demon hehe

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  21. Thank you. Thank you. Thank you. X's infinity. It's like Xmas all over again.

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  22. I was reading that Catalinbread recommends trying it out with lower voltages. Has anyone tried this at all? Maybe with a starve control or something? I have my parts on order so I'll try it out myself. I'm looking forward to another doom pedal.

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  23. Looks like nte469 could be equivalent
    http://www.weisd.com/searchresult.php

    http://www.nteinc.com/specs/400to499/pdf/nte469.pdf
    https://www.fairchildsemi.com/datasheets/PN/PN4393.pdf

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  24. I just built this using 5 J201s and a 2n5088 for NPN - and it works just fine. It even sounds pretty decent. I love the range control. The presence I could live without (ll it does for me is make the guitar darker). It has plenty of gain though I would like a little more - but these are just my initial results, I have not tried any substitutions yet at all (except of course the listed trannies since those were what I have on hand).

    I will probably try some higher HFE NPNS, and I have some newer version PN4393 trannies coming. So, I will see how much different it sounds (if any) but it does work with J201s.

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  25. I used 2n5457 and a 5088 to build mine. It turned out nicely and fired right up.

    I will probably get burned at the stake over a pile of broken SG necks for saying so, but my build likes a hot pickup best.

    I did socket the 47R resistor referred to in the post up above and to my ear 220R gave me a slightly more rich, less fizzy sound.

    I am afraid mine does not like vintage output pickups even with the 47R. My Seymour Duncan P 90s do not drive this unit quite enough to get to the sweet leaf tone. Normal humbuckers do much better and EMGs really make this unit come alive.

    The interaction between the range control and the presence are where the magic happens on my build. The grind is very close to Iommi's Master or Reality tone and that is a tone I have never really come this close to before. Believe me I have tried! Been playing Sabbath since 78. Thanks for posting this build. I love it!

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    1. I possibly might try the 47-220 sub. Why not eh?

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  26. Do you need to match the JFET's in this build.
    I've read that you need to match JFET's in, amp in pedal form builds

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    1. Nah not really..? I haven't match JFETs in any amp pedal builds.

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  27. I just got in the PN4393 trannies and they sound excellent, but not much different from the J201s (maybe just a bit richer - but a very small differential, maybe 10%).

    You can use just about any NPN in the non-Jfet position. I also got some BC184s in my order for the JFets, and they do sound good. I had also tried a BC109 in there. I also had a 2N5088 that sounded fine - so any decent NPN sounds good - try whatever you have.

    As for the Jfets, I just tried mixing in two J201s (for one of the lower pairs), 5457s and I prefer the sound of matching jfets all around.

    If I were buying parts for this, I would get the PN4393s. I think I may have found a new Jfet I can use in a lot of applications.

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  28. What is interesting is how much this circuit interacts with your guitar controls. I have never seen one do it so much. When I turn my volume control down it hits a points where the guitar signal stops, but the circuit hum gets much louder, full off on my guitar and the noise is really obnoxious.

    I have only tried my SD super distortion, but the tone is fine with it full on. Rick and thick but not too hairy.

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  29. Just built it using MPF102's and a 2N5088. Unless the MPF102's aren't a good fit for this, this pedal doesn't like a dirty amp. I have a modded Orange OR15 and play with a fairly dirty tone and use a PRS SCT with Lace Hammerclaws and they don't play nicely together. The Range control also makes turns the signal to mud and gates everything as it's turned up. The only other Jfet's I have are a single 2N5457 and four 2N5458s. Not much difference. I guess this isn't a good fit for my rig or the MPF102's aren't suited for the Sabbra.

    Anyone else use MPF102s?

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    1. I think I must have screwed up my build. I found out if I flip the BC184 it works better. I tried a 2N3904 and BC550 as well and it worked if reversed. I also put in 2N5457s and there was no change from the MPF102s. However, I don't have nearly as much gain as expected so I'm assuming I messed up somewhere in my build. I have a feeling this wouldn't work too well as a way to shape my dirty tone anyway.

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  30. just boxed mine in a 125B. Pics:

    http://i302.photobucket.com/albums/nn84/isolditnj0125/image2.jpg
    http://i302.photobucket.com/albums/nn84/isolditnj0125/image1.jpg

    It's got that elusive "devour your son" tone.

    Sounds more or less like the demo video, but like many others, I've got quite a bit of noise. Has anyone attempted any of the suggested tweaks?

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    1. Rad. Looks great, good art. GOYA is a cool name for a pedal. You should glue/solder those transistors in, just in case ;)

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  31. Have just finished testing this effect, and here you have my two cents:

    I've used a 5088 instead of the BC184, don't think that there's a great difference in sound. Used too original MPF4393 from Musikding.

    First thing that I could notice is that the circuit is not really noisy, and I'm sure that if boxed, it would be even a quiet one for such gain. Check your boards if you have noise problems, because it's not a normal behaviour. Maybe using different jfets is what brings the noise to the effect.

    Second: Range pot is mandatory to be reverse log. Even a lin one is pretty useless and all the juice is in the last 20% of the sweep.

    Third: It sounds fine on the clean channel, but really shines on the dirty one. Just crank a bit the channel and the Sabbra Cadabra really delivers.

    Fourth: Really dependant of pickups. With humbuckers, sounds great but with single coils is hollow and thin.

    Fifth: I really don't like the effect :P Yeah, it's great to nail some Iommi tones.... but it's useless for any other job.

    Still don't know if I'll box the effect. To get with an instant click the Master of Reality and Vol. 4 tones is great, but... does it really deserves a place in your pedalboard?


    So, If you play in a Sabbath tribute band, or play some Iommi cover's, you'll love the effect, otherwise, it will become a boring one after half an hour playin'.

    Up to you, dudes :P

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    1. awesome write up man. i've wondered what happened to you. you seemed to have disappeared. lol

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    2. No problem Zach :) I'm a bit busy now, and have less time to build and play, but I still read the blog very often and build some effects :)

      J.

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    3. i hear you on that one. no joke, i was going to send you an email today to see what was going on.

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  32. Great to see everyone again. Been waiting a long time for some new posts on this superlicious board.

    Also, some new builds will be added soon to the FuzzQuest.blogspot. Really excited.

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  33. FYI, my first build used 2N5457's and it was extremely noisy. Subbed out a million of them with the same results. Recently replaced them with MPF4393's ordered on Ebay and now it's nice and quiet, and the volume is much more usable. With the 2N5457's the volume was earth-shattering, even at 9:00. Now there's still loads of volume on tap but it's a bit tamed.

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    1. So the JFET used is important to the circuit eh... hm.

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  34. Doron - many of us are in the forums: http://guitar-fx-layouts.42897.x6.nabble.com/

    By the way - I am still struggling with noise on this one. I am using the recommended PN4393s along with a BC184 - it sounds good but the noise just won't go away. There is something in the way this build interfaces with the guitar - even when I turn my guitar volume off - the noise just gets worse.

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  35. J201s are really noisy. I also tried most others; 2n5457, 2n5457, 2n5484... the PN4393s seem to be the best match, but I am going try other parts for the BC184 and see if I can tame the noise.

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  36. Can anyone help a noob? The layout has a couple of board connections to multiple lugs on pots (i.e. Range 1&2). Does this mean connect them in parallel? In other words, should I solder a lead from the board to two separate wires, then connect each lead to its respective lug? Or can I connect a lead to lug 1, then connect lugs 1 and 2 with another wire? any help would be appreciated!

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    1. There's a few ways you can do this....

      Take 2 wires from the same hole
      Take 1 wire from the hole and strip the other end slightly longer and lay it across the 2 pot lugs and solder. (my preferred method)
      Take 1 wire from the hole to 1 pot lug and bend the other lug until it touches and solder.

      It really doesnt matter how you do this as long as that row is connected to the pot lugs physically (without going through electrical components)

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    2. Thanks Ciaran! Looks like both ways match up with what you are saying. I really appreciate the help!

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  37. so is this site dead? Anyone wanna email me some info on getting the layout creator working on mac. i have the newest osX (terrible- nobody update to mavericks- worse than windows 7 was when it came out). Anyways, I have some circuits I think would benefit the site and id like to try my hand at layouts and keep this site going. you all have given me so much that i just have a strong desire to give something back! my email is ckeibler85@gmail.com if yall care to help me get a layout creator working. thanks!

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    1. The comments section is alive as ever, but I think Mark and Miro are busy at the moment with IRL lives? Were you using DIYLC? I have attempted that and it seems to work but I don't really get it. Mavericks is shitty yes, but at least it does run things that it can run haha.

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  38. Far from dead - just head over to the forum. It's all going on there!

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  39. Been playing some grea tSabbath riffs after building this one. What a great pedal but getting a 750k resistor was a PITA, but hey definitely worth it. Thanks for the layouts as always, this place rocks my soul.

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  40. Hi all! I've built it using BC550 and 2SK117 as FET's and it sounds like crap :( I think I screwed up somewhere but i can't find out where. Mine FET's voltages look really weird, so can anyone post them, please? Thanks in advance and sorry for my poor english :)

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  41. Did you check the transistor pinouts for your substitutes?

    I'm away from home or I'd measure the voltages in mine for you

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  42. It is good to read. Hope more information. Thanks

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  43. @Travis - it's unnecessary. I've already managed to fix this. The issue was ultra thin solder bridge between tracks. I also switched from BC550 to 2N2222, cause BC was really noisy. Now it works like a charm. Anyway, thanks for your effort :)

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  45. I have a question about substitutions. I have read through all of the comments here, but I figured since the build has been out for a while, I was wondering if there were some solid substitutions specifically for this build. I am new to diy pedals (this is my second build).

    What would be the best sub for the 1N5817 diode:
    1N5818, 1N4001, or 1N34A

    What would be the best sub for the MPF4393 transistor:
    2N5457, J201 or MPF102

    Any information would be greatly appreciated. Thank you.

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  46. Wow. This was the 4th pedal I've built from this site and I just gotta say this site is awesome. I just finished band practice and played this baby for our Sabbathy song and damn... it nailed the tone and totally cut through the mix. Thanks guys for such a great site. Still pretty new at pedal building but you guys made it easy with your tutorials great layouts. Fit it into a 1590B enclosure quite easily.

    I used a 2N5088 for Q1 and J201 for the rest. The distortion initially was a little sputtery but then I realized I missed a resistor, doh! A little noisy of a pedal when not playing but I only click it on when I need it. Cleans up really nice when you roll down the volume.

    Awesome stuff! Keep it coming, I'm totally nerding out on it.

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    1. Hi Ralf, I am in the midst of building this (very much a beginner). I have the board populated and beginning to plan the test and boxing. Where did you connect the LED on this board? I don't see it labeled and not sure where the positive LED should connect to.
      Thanks.

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    2. Use the off-board wiring instructions here:
      http://tagboardeffects.blogspot.com/2012/02/offboard-wiring.html

      Its really easy or you can get one of those 3dpt switch boards from various PCB sites to make it even easier and cleaner looking on the inside.

      Good luck!

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    3. That looks perfect. Thank you. I just tested my build on the breadboard and it sounds fantastic (my second build). Can't wait to box it up. Thanks for the help!

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  47. Replies
    1. Output 2 is lug 2 of the volume pot

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    2. And if you check the build notes below the layout itself it states "Output 2 to Output." So you will run a wire from lug 2 of the output pot to the correct lug on your 3pdt switch.

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  48. I used this pedal on 'War Pigs' last week at the Eagles in Brazil, IN. (song came out when I was a senior in high school 1970). I sampled the air raid siron on my JamMan and people eeeeeet it up!!!

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  49. Capacitor class! I just built my second Sab Cab pedal and discovered something. Throw away ceramic caps over 270pf!! They create noise. I know this may be old news to many but for some, it will fix a lot of hissing.

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  51. Out of curiosity...if a guy wanted to take the Naga Viper element OUT of this build, how much of that upper left corner would need to be bypassed, and from where to where?

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  52. You would omit the transistor, 1M, 4.7K, 220K, 68K, 10K, 47Ω 4n7, 68n, 47pf, 47uf, the short link and the two cuts next to the short link.

    Input wire would then go where it is currently marked Range 3 on the layout

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  53. please, can someone tell me what are the red squares with circles inside? I'm not very keen on this.

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    1. Hey Matt. First off welcome. Second to answer your question those are to represent where you're going to make cut in the copper tracks. Before you do anything I would read the tab at the top marked "build guide" before building anything. Also, I would highly, and I mean highly suggest you build something simple first, not a omplicated build like this. There will be less to go wrong, and easier to debug if there is a problem.

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  54. Hey, can i sub the 270pf for a 220pf?? Im not sure what that would do...

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    1. Yes you can, no noticavle difference. I used a 2n2222 and 5457s but the bottom left two i used 2 j201's with a lil bit more clarity through the strings. I love how responsive this pedal is to the controls and how it colours in so many different ways. Love it!!!

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  55. Build it with one 2n5088 and 5 MPF102 - sounded awful.
    After (useless) Debugging (couldn`t find any faults,
    replaced the MPF102 with MPF4393 now it`s sounding nicely.
    So i wouldn´t recommend the MPF102, too.

    Still want to to try a 2n2222for the 5088.

    Thanks for the layout - this site is a great inspiration :)

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  56. Quite a decent distortion. I noticed my build had a squeal going on at higher gain settings, so I changed the 47 ohm resistor to 470 ohms. Worked well and the gain is still high. I also tried a few different transistors in the boost section, ended up liking 5088 best.

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  57. Hi there
    I've got a few questions to this one ..
    The Q1-Q6; are they the ones marked as CBE and DSG on the board?
    And it says "Output 2 to output" ... but I can't find "Output 2" ... only 1 and 3 ...

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  58. Hi, i built this pedal last week and the volume pot is showing a weird behavior, it never mutes the sound, even if turned all the way to the left... Actually, the volume is really loud even with the volume pot on zero. Does anyone know what may be the problem, or can think of a solution? By the way, I used a 2N2222 for Q1 and MPF102s for the Fets. Thanks in advance

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    1. I believe there must be a mistake somewhere in your build, like wrong component placement or wrong wiring.

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    2. Yeah, last night I figured out that I used an old pcb layout which didn´t have lug 1 of the volume pot connected to ground. Made the correction and now it is working fine. By the way, I used 2n2222 for Q1 and mpf102s for the Fets. Unlike some have posted here, I think mpf102 does work for this project, but you have to try them in different positions on the circuit using sockets (I did this) to find the best combination (matched fets would be nice I guess). I little bit noisy, but not that much considering the high gain structure of this pedal, and probably it will be even better when boxed. Iommi rules!

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  59. Boxed the pedal, and it's working great! Grounding everything propperly is relly important building this pedal, to avoid excessive noise. Mine is quiet. Again, differently from what some people said, it worked great both with a SG tunned in C# and a telecaster (single coils) in standard tunning. And not, it is definetely not a one trick ponney. There are lots of sounds tweeking its 4 knobs. Works great also rolling the guitar volume knob down. Fantastic pedal, I love it.

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  61. Anyone ever fool with the tone stack ? From what I gather the 22k 33k and 220k in series at the bottom of the board are fixed mid/bass/and treble values? Couldn't they be replaced with pots ?..I am about to build this thing and I have room for another pot I could switch in or out.I am going to guess if I had to choose one the mids (22k) would be the best option?

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    1. It also looks like any pot I toss in there for the mids will need that 22n cap on its wiper ?

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  62. Can someone post good voltages for the transistors? My build has a significant volume drop when all knobs are maxed. Voltages might help me narrow it down.

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  63. I get output and all the knobs seem to function properly, but there's a significant volume drop.

    Using an audio probe, I've figured out that a volume drop seems to happen at the 100k resistor after Q5 that isn't really being recovered by Q6. Is that supposed to happen?

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    1. Pinout on my BC184 was different than I thought. Got it oriented correctly and it sounds much better. Still gonna play with some component values based on other feedback above.

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  64. I think I've got it working right now. Here are my voltages. Numbered this way

    T1 Q5
    Q2 Q4
    Q1 Q3


    BC184
    C 5.8v
    B 2v
    E 1.5v


    2n4393 1
    D 4.8v
    S 1.3v
    G 0v

    2n4393 2
    D 9v
    S 5.7v
    G 4.2v

    2n4393 3
    D 4.3v
    S 1.1v
    G 0v

    2n4393 4
    D 9v
    S 5.7v
    G 4.2v

    2n4393 5
    D 9v
    S 5.6v
    G 3.9v

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  65. This comment has been removed by the author.

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    1. Never mind. Figure doubt I soldered the very long jumper 1 hole too high. All works now!

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