Monday, 1 April 2013

MXR Blue Box

So. It's April already. This one is the last post from me for today. I do believe there lots of you who have been waiting to get your hands on a doable octave down circuit. Here it is. You should probably try this with a fuzz in front of it :)

Edit! Here's a link to John K's modded layout, which will sound cleaner and has 1/2 octaves on a switch:
http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BlueBox/MXR_BlueBox-Final-Verified.png
Huge thank you John!




112 comments:

  1. Awww man!

    You'll be the end of me... :)

    I have all these builds lined up already and you keep coming up with things that have been on my shortlist for months/years!

    I even considered getting a Lowrider from Madbean only to use it as an octaver (or doing my own pcb from his builddoc) but once again, now I don't have to! :)
    This one won't get built for at least a month but I'm definitely building it.
    Thanks man!

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  2. Been waiting a long time to build this one

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  3. Maybe its the lack of coffee in me this morning, but does that 56k resistor to the adjacent left of the asterix'd 56k not connect with anything else?

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    Replies
    1. Damnit. I swear i checked the whole thing over like 5 times before posting.. I'll check it right away...
      +m

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    2. Updated. That was apparently leftover resistor, as it wasn't supposed to be there in the first place. Now the resistor count matches the schematic. :)

      Thanks Matt. Keen eyes usually help people to save a lot of time. Hate it when i go blind on these bigger layouts..
      +m

      Delete
  4. Miro, would you mind also putting together a vero for the crazier version of the Blue Box, the original script logo version with two LM741s? It has a certain something where it tracks worse and thus produces crazier results.

    Link to a populated pcb (that I have built and used, so it is verified) below:
    http://i55.photobucket.com/albums/g146/icecreamterror/MXR-bluebox2.gif
    (More info including the PCB without parts in the MXR M-103 blue box thread at FSB):
    http://freestompboxes.org/viewtopic.php?f=33&t=21320&hilit=blue+box

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  5. You need a layout with the octave splitting mod so you can choose between 1 or 2 octaves down. Im pretty sure you just put a switch between two of the pins. I can't remember which ones though.

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  6. Built it. Works. This one is going to be boxed tomorrow. And it's going straight to my pedalboard. Love it.

    Used 2N3904s for transistors, JRC4558 and buffered CD4013 for ICs. The flip-flop chip seems to give out some slight trigger noise every now and then, but as that was my last chip in stock, i can't swap it until i get more..

    This was pretty straight forward and quick build after all.

    Absolutely. Love it.
    +m

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    1. Excellent, just like the olden days! :o)

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  7. Where do you folks score 25k lin pots? They have really been a thorn in my side (needed for just about every build I'm planning) and I've only found decent quality ones on Banzai (too expensive, though)?

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    1. Forgot to mention, but i used 50K linear for both. Other schematic that's available has them for 50K. So that will work fine here.
      +m

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    2. Great info, that's what I'll use as well then!

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    3. Now that i woke up i played with circuit some more. I'm loving it even more. Trigger release noise (sort of an fading fizz) vanishes with blend turned back to about half way. That is something that 25K pot could probably make better, but i'm really not that bothered with it. This is pretty noisy thing anyway :)

      But back to 25K issue.. I'm in that same boat. I get my pots from tayda, and don't want to mix any other shaft types with those to keep my pot stash in uniform. Call me slightly autistic, i probably am. Since tayda does not have those in stock, regardless of numerous requests, my "solution" has been to use 20K where it's approriate and for when the design really needs 25K - i've been hacking my way through it. Meaning that i take 50K linear pot and then i have two options that are affected by the taper i want. If the taper doesn't matter, i usually solder 51K resistor between 50K linear pot's lugs 1 and 3. That turns it sort of an log pot, but the value is close to 25K. Other option i use is to take two resistors, 24K and 27K and solder first one between pot lugs 1 and 2. The second one between lugs 2 and 3. Voilâ. We have twisted taper 25K pot.

      If anyone has cracked how to turn the Fuzz Face style circuit's 1K linear pot into rev log, i'd be interested. I have a clue about it, but i'd like to hear if anyone does it - and how they do it.
      Good read on the subject: http://www.geofex.com/Article_Folders/potsecrets/potscret.htm
      +m

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    4. Yeah, makes sense... although I'm really not sure (been a while since I was in school :) ) how to differentiate needs vs wants, when the B25k is really _needed_ and when it's simply nice to have but not at all critical.

      Delete
    5. And also, I was always under the impression (only used it once or twice but seems to do just that) that 2k across B2k would give you C1k?

      Delete
    6. Gut feeling :) That's what i use :D

      For some tone controls that have 25Ks with one lug to ground on them, i have once or twice place a 5K1 resistor between the ground and that lug, thus eliminating 1/5 of the sweep from the bottom end. So that could be one alternative too. It doesn't suit every situation, but it's ok for some.
      +m

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    7. 2K across 2K pot makes it closer to 1K log...
      +m

      Delete

    8. OK, I guess I remembered that one wrong :) but from your own RGK link (really should have read it beforehand :) ):

      "In a bit of good fortune, if you hook up the tapering resistor from the CW or hot side of the pot to the wiper, the pot emulates a reverse log pot, just as well as it did a log pot when hooked to the CCW side. "

      Is that not what you need?

      Delete
    9. Basically. Haven't tried it yet though... Most FF derivatives scream for rev log to the fuzz control :)
      +m

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  8. Some people mod this by changing the 1nf cap to a to 0.0022uf. This gives a volume boost and different tone. http://www.youtube.com/watch?v=yIaXXJMAAFI

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  9. Aaand here we go:
    http://mirosol.kapsi.fi/varasto/boxes/BlBo.jpg
    +m

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    Replies
    1. More i play with this, the more i love it. This is definitely the most fun in a build i've ever had.
      +m

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    2. Nice one, Miro!

      - what kind of paint is this?
      - more importantly :) , do the pots light up?

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    3. Thought i'd try something different. It's acrylic paint and water based clearcoat laquer (that stuff is awesome). No. The knobs don't light up :)

      Used acrylic for two upcoming Klon clones too (ochra yellow). Thin layer, and it really looks like gold with that laquer. Sadly i need to build two of everything now, since the other one always vanishes. It's the only way i get to keep some some builds for myself :)
      +m

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    4. It looks like you only painted the front face? Did you clearcoat the whole thing of just the painted part?

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    5. Yup. Painted just the top. Laquered it all the way though - after sanding the sides with 800 paper.
      +m

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    6. I'm looking into handpainting at this point so please forgive the gazillion questions... :)

      So you sand the whole thing first, paint the top (looks pretty cool, never seen one that's only painted on top) and then clearcoat everything? Do you put primer before paint?

      Delete
    7. Not for these.. It'll stay as long as it stays :) Laquer helps a lot though.
      +m

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  10. Really excited to try this one out - does anybody know where the switch would go for the 1/2 octave switching mod? Sounds like it could give it quite a bit more versatility.

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  11. Miro- did you end up going with the 56K resistor or the wire link on your build?

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    Replies
    1. I used the resistor. Apparently it'll work with and without it.
      +m

      Delete
  12. JFC! You're right Miro, this effect rocks! After building the R. Mayer Octavia (octave up), I wanted to get a octave down, so this one was the logical one to build.

    Used a Motorola MC14013BCP, as I have no CD4013, and the result is amazing

    Both are great, I'm thinking about a double pedal with both, should fit with no problem in a 1590BB.

    This build is extremely easy, don't let its size stress you, the only boring part were the 17 links, but after building Sabro's Zombie Chorus it won't frighten me :P

    BR

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    Replies
    1. It was pretty straight forward :) Very fun effect.
      +m

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  13. Is this an exact copy of the MXR Blue Box circuit? Blue Boxes are notorious for a volume drop when they're turned on. Is that the case with this version or has the mod already been applied?

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    1. Schematic doesn't state if it's modded. But for my build, it's not dropping the volume.
      +m

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  14. would some of successful Blue Box builders help me out? I'm sort of racking my brain in an attempt to get this working...I've built a few working effects, and have a broad/basic, but good knowledge of electronics, but this one has got the best of me. my bypassed signal is clear but when i turn on the effect, no signal passes and neither of the pots has any affect. i've been through the build and troubleshooting areas of this site several times, without luck.
    i've got extra components (3PDT stomp, jacks, JRC4558's, CD4013's, and 2N3904's). i've swapped them in and out several times without luck. i've printed out the datasheets on the IC's and Tranny's but i'm having a hard time figuring the problem out. any ideas?!?!
    i also have voltage measurements at all IC pins, transistor pins and diode leads if that will help...thanks in advance!

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    1. Please, tell us your voltages, would surely give a hint. In the while, just take in mind that this build is very easy, but confusing, as the resistors are spreand trough many rows, ans is easy to place one of them one hole up or down.

      Check carefuly all components location, and trannies orientation as first approach.

      BR

      Delete
  15. good suggestion. i've checked and double checked so i am 99% sure that positions are correct. here are voltages, with a battery that measured at 8.75V:

    IC1 -
    pin 1: 8.42V
    2: 5.71V
    3: 2.14V
    4: 0.02V
    5: 4.09V
    6: 3.96V
    7: 0.27V
    8: 8.62V

    IC2 -
    pin 1: 0.02V
    2: 8.60V
    3: 8.60V
    4: 0.02V
    5: 8.60V
    6: 0.02V
    7: 0.02V
    8: 0.02V
    9: 0.02V
    10: 0.02V
    11: 8.44V
    12: 8.60V
    13: 0.00V
    14: 8.60V

    Transistors (from L to R when viewing the layout):
    -E: 0.02V -B: 0.54V -C: 0.02V <--left
    -E: 0.03V -B: 0.56V -C: 0.02V <--middle
    -E: 0.02V -B: 0.06V -C: 8.42V <--right

    hope its just a stupid mistake...

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  16. diodes are 1N914 and transistors are 2N3904

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    Replies
    1. At first sight you have a grounding isuue, check all ground links and look for tiny bridges.

      Check too IC2, as is grounded and should not be.

      Tell us if it's been of help.

      BR

      Delete
    2. Awesome...thanks a bunch for the suggestion and looking things over. I'm at work right now but when i get home i'll get a magnifying lens and knife some voids. when you say grounding issue, i'm pretty sure that you mean on the board and not off-board. i'm using the off-board wiring strategy on this site and all of the off board grounds appear to be fine. i'll check pin 9 specifically.

      thanks again.

      Delete
    3. You're welcome :)

      No, with grounding issue, I mean that some rows that shouldn't be are linked to ground, for example the IC2 pin 9. This row is the Output wire one, so If is grounded, you won't get any sound.

      In the other hand, ground voltage should be 0, and you have 2 or 3 milivolts in every groundep point, so, something's wrong, surely a tiny bridge as usual.

      BR

      Delete
  17. what kind of caps did you use for the 10uF's and the 47 uf's? can i use electrolytic caps instead? if so which side should be negative and which positive?

    thanks for the layout.

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    Replies
    1. Hmm.. Those images aren't electrolytic? Negative side is marked, just like in the caps themselves.
      +m

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    2. Oh okay, I see it now. thanks a lot.

      Delete
  18. I just built this one and it sounds great. I also modded it a little so it's 19 x 22 and added a 1 octave below/2octave below switch. i'm just waiting for the enclosure to arrive so I can box it up.

    pic of the board:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BlueBox/MXRBB-03.jpg

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    Replies
    1. Super neat looking board once again! Care to share the details on the mods? There seems to be a few things going on in there.. :)
      +m

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    2. I just finished my build of John's version. I have a question about the level pot. There is a lead coming from the board that is labeled Level 2 but in the notes it also says Level 2 to output. Is this a double link( board to the pot and then out , on the same lug) Any help would be appreciated.

      Delete
    3. Hey yes it's a double connection. The level 2 connects to the board and the output.

      Delete
  19. when I added the 1 octave switch, it was really glitchy until I lowered the voltage going to it with my benchtop power supply. adding a 470 ohm resistor to the 9v supply fixed that. it also was a bit too distorted for me so I changed the 1K resistor to s 4.99K one in the the gain stage. I also omitted the 10n cap across lugs 2 & 3 on the volume control because I found the pedal to be too bright (AKA, Keeley C11 mod).

    here's my modded layout based on your's:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BlueBox/MXR_BlueBox-Final-Verified.png

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    Replies
    1. Cool! I'll add that link to the post if you don't mind?

      Liked my build so much that i just had to buy an original. Waiting for it to arrive. Guess i should get rid of the first build, build your mods and keep that with the original.
      +m

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  20. my enclosure arrived today so this baby is done. ;-)

    pics:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BlueBox/BBox-01.jpg

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BlueBox/BBox-02.jpg

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  21. Just finished another board as the first one i had got ripped from me by one local syth dude :)

    The value of the Blend pot makes a huge difference. With 20K this is pretty close to the original (which i now have too). 50K makes it pretty noisy and cool - 100K makes it f*n animal.

    Original box sucks by the way. Both of my clones are way louder and more out of control. Anyone interested in buying that original off of me? Bought it new and tested it once :)
    +m

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  22. Hi everyone.

    I tried this build but cannot get it to work properly.
    Bypass works ok but when the effect is engaged what I get is not what I expected. I get a light distortion sound (a bit like a fuzz), some notes get choked (some don't sound at all), and very little sustain (almost like the battery is dying). And I hear no octaves at all. So I've built a lousy fuzz pedal.

    I've triple checked everthing I can think of and now I'm clueless.

    Any ideas on what might cause these symptoms? My best guess is IC2 not working at all. How do I check this? I'm noob at electronics.

    Thanks for any help.
    César.

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    Replies

    1. I'll start building a BB this afternoon if I don't get sidetracked. If you aren't in a hurry we can compare voltages when I'm done.

      Delete
    2. I've built two of these, so i know the layout is good. Check transistor pinout and IC2 orientation.
      +m

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    3. I am having the same problem. I'm using the PCB layout featuring tonepad.com.
      I do not want to give up! but all my components are well targeted and i already made the changes suggested in the Tonepad's pdf.
      Nothing, I still have the effect of fuzz, but some choked notes (some do not sound at all), and very little sustain (almost like the battery is dying). But sometimes I hear octaves and other times do not. Pleeeeeeaaaassseeeee Heeeeelp !!!!

      Can this problem be fixed by changing the CD4013 by a new one? i mean, mine was a new one when I put it onto the board....

      Delete
    4. Did you guys get this sorted? I've got the same issue... can barely hear the effect, but plenty of fuzz sound which dies away suddenly instead of sustaining. It does sound like a dying battery. I've reflowed all solder joints, triple checked for bridges and swapped out both ics for new ones with no luck.

      Delete
  23. Just a few notes - I got an original Dunlop/MXR reissue some time ago and o'boy it sucked. Traded it away already. It didn't go over unity and it wasn't nearly as wild as the boards i built with this layout. Yesterday i finished two more boards and i can strongly recommend 100K lin pots for both, blend and output. You'll get better output levels (not that there's anything wrong with the level with 50K pot) and slightly less flip-flop trigger noise, apperently due to oct and non-oct signals not feeding back to each other as much.
    +m

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  24. Is there an equivalent for the JRC4558 that would be suitable for this circuit?

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    Replies
    1. Any dual opamp should do just fine. TL022, TL062, TL072, TL082, NE5532, LM358, LM833, LF353, LF442, TLC2262, TLC2272, OP275, OPA2604, AD712 and so on. You should be able to get JRC4558 for cheap through ebay though.
      +m

      Delete
    2. I just didn't feel like ordering more parts. Thanks, man!

      Delete
  25. Aaaand my build of this, temped to try Johns layout tho as it was to noisy for me: http://instagram.com/p/czGsiYRWMz/

    ReplyDelete
  26. Here's my build:

    https://lh4.googleusercontent.com/-vmkOlQyUxNw/UhdsDv08usI/AAAAAAAABAA/keRVLjyE0cI/w579-h772-no/IMG_2834.JPG

    https://lh4.googleusercontent.com/-n67QAakykqI/Uhdsh3fDx7I/AAAAAAAABAI/uXvmrTwmxko/w579-h772-no/IMG_2839_2.jpg

    https://lh3.googleusercontent.com/-EItsBzF3x9Y/UhduX0i97jI/AAAAAAAABA4/CiABaUquLi8/w1029-h772-no/IMG_2841_1.jpg

    https://lh5.googleusercontent.com/-lrfhbWiw314/Uhdr4mHl-oI/AAAAAAAAA_4/Sc_YFkoPwqA/w579-h772-no/IMG_2821.JPG

    ReplyDelete
  27. so i went ahead and built this and the fuzz works but i'm not getting much of the octave. any idea what might be causing that? when i turn the blend pot not much happens, just a little of added noise.

    ReplyDelete
  28. I'm probably going to build this tonight, but reading through the comments it seems that there's a lot of mention to it being noisy. Anyone thought to put a filtering cap on the power? Seems to me 9v and Ground tracks are sitting perfect spacing begging for a 100uf to be plugged in there. Would that make sense?

    ReplyDelete
    Replies
    1. The noise i'm referring to comes from the flip-flop rather than from the power supply. The noise is not at the fuzzed signal, but the flip-flop making very strange (and cool) excess noises when it is gating.

      Even if there is something "wrong" to the layout, it is about a 100 times better than the original Dunlop/MXR unit. :)

      Try bigger value pots for both. 100K is the bomb.
      +m

      Delete
    2. Cool, thanks for the advice on the pots! I saw that John K had upped the blend to 50k, but I'll give this a go at 100k.

      On another note, it looks like I'll need to replenish my 56k resistor supply after this build. This sucker burns through a dozen of them! I'll fudge a few with 47ks since I don't think the exact value is going to be mission critical ;)
      -John

      Delete
  29. Just went to start this build and realized I don't have any stripboards that large! all of mine are only 19 high! Any good resources for where to get larger boards in the US? I know Mouser and Futurlec have them, but was wondering if anywhere else had some better prices that anyone may know of offhand!

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    1. This comment has been removed by the author.

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  30. hi there to everybody! i have a question with a quick answer. does anyone tried john k's layout?i've tried this one and i want to be sure if there is a double link at level2 (board-pot-output) cause it's the first time i saw this in a layout and i'm not so good in finding mistakes...also i'm new in the pedal sport so...thanks anyway

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  31. just a review.... i've tried john k's layout, and it works fine, but the switch doesn't do anything to my ears...the only thing i've changed is that i've used 47k lin for blend and 100k lin for level...so maybe i did a mistake somewhere or i can't hear any differences in the octaves...if someone tried this layout too and can help me out, it would be great..!

    ReplyDelete
  32. Hi, I just built the Blue Box according to the original vero layout linked above...but all I get when I turn it on is a slow and steady pulse sound *tick* *tick* *tick* with no instrument sound at all. The level pot does change the volume of the pulses, the blend pot does nothing. Any clues anyone where to start? I'm feeling a little lost... :( Thanks in advance!

    ReplyDelete
  33. I just figured it out, small stupid mistake, it seems to work now! ...I almost thought I fried a transistor or something...

    ReplyDelete
  34. more than one month on that (among other projects too), and i have one more report. Build john k's as i said and first of all i get a very small amount of octave change, the switch doen't work for me, and the volume as every blue box from what people say is too low. at the layout there's no 10nf cap as in the photo of john k's build and second there is a no-need double link between the ics(whitch doen't matter anyway!!!). to get more volume i've changed the 2.2M intput resistor to an 1M. changed the10nf output cap to a 330pf(!), and the 1nf cap to a 2.2nf. i didn't knew what i was doing, just playing with all that i've read about moding the bb.all these worked for the volume boost, but still nothing on the octave thing and switch...please someone help here...if you what i can post voltages too..

    ReplyDelete
  35. is it a good sign that my 4013 is dead if i get same fuzz sound (but no octave effect) with the ic onboard and offboard?

    ReplyDelete
  36. your BB version was my first build. Thank you very much for the vero-layout! I have a question about the trigger noise: is there a possibillity to reduce it? I used very cheap ceramic caps. Are they responsible for the noise I hear when the strings are swinging out?
    w

    ReplyDelete
  37. miro i think there are a few mistakes with this vero.

    did you do it from tonepad schem right?

    that's the only pedal that i couldn't make it work...for months it was a pain in the ass and finally after 2 failures i reaped off both boards. but today i checked the schematic and there are a few mistakes.
    if i'm mistaken then i would be very happy if you could explain to me.

    first
    the 56k resistor the 3rd from bottom left shouldn't be there at all.i mean the one that connects the collector of q2 straight with the 47nf cap.

    second
    the 10nf cap bottom right shouldn't go from level 2 to ground but from level 3 to ground

    and third
    some caps are 47μf at your layout, but at the schematic they are 1μf


    i know that it's been more that a year that you posted it and i may look like stupid, but lot of people didn't make it work so i wanted to search a little bit more.
    hope you see it and answer
    thank you for the fantastic work you and mark do

    ReplyDelete
    Replies
    1. No, it's not from tonepad schem. http://web.archive.org/web/20051014171114/home.houston.rr.com/cjlectronics/schems/bluebox.jpg

      And. I've built at least six of these boards without a single issue. Plus i know people who have built this successfully too.

      First - Depends on the schematic. Schematic i used has a note on that resistor "I've seen this shorted in some units"

      Second - No. See the schematic.

      Third - No. See the schematic, there are two 47µ caps in there.
      +m

      Delete
    2. I've built (and boxed!) this effect too and worked first time with no issue. Works great!

      Delete
  38. ok guys...i see...i was looking to an other schematic.
    those differences i've found were at the tonepads schem.

    i guess i have to try this for one more time...thanks a lot for everything
    if something goes wrong again i'll ask help...

    ReplyDelete
  39. Yikes! Built this on John's layout, but almost no voltage gets past the 470R resistor to IC2 Pin 14 (the 470R takes 9.08 V down to 0.7 V). So I replaced the 470R with a jumper, sending power directly to Pin 14, as in this layout... the CD4013 got burning hot immediately. Smelled like burning as well. Wondering if anyone has a guess what's going on there? I've run over this thing a dozen times and everything is placed right, and I don't see any solder bridges or cold joints.

    ReplyDelete
  40. i think that you have a short somewhere. there's no way that the 9V can get down to .7V with a 470R resistor.

    ReplyDelete
    Replies
    1. Thanks John. I'm going to keep looking it over. That drop is happening pretty immediately in the circuit, so I would think there's some short near the 470R, but I haven't found anything yet. It's frustrating because there isn't much around the 470R.

      Delete
    2. I can't find any solder joints (the back of this thing is ugly now, everything has been razored), and all components, jumpers, and cuts are placed properly. One thing I did notice is, if I remove IC2, I have 6.9V in the socket of Pin 14. When I put IC2 back in, I get the same 0.7V on pin 14. I'm not smart enough to know what that means, and I really don't understand what IC2 is doing, but maybe it's a red flag to someone else..

      Delete
    3. I finally got around to ordering a new CD4013 - works perfectly now. Thank you for all your help. I guess the first chip was just completely DOA.

      Delete
  41. I've built one of these with 100k pots an love it. I'm building another one for a friend and I only have 1m pots you think thst too much? Probably a dumb question but I thought I would ask before I try it out

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    Replies
    1. I went ahead and built it with the 1m pots and it sounds nasty I love this pedal. I keep getting antsy to finish a build and trying to sub parts I hate waiting for parts to be shipped to me

      Delete
  42. Hi..Can someone please advice what kind of switch should I use for the 'octave blend' function and how this is wired? I'm using John K's mod. thanks..

    ReplyDelete
    Replies
    1. Use a SPDT switch. Wire Sw- 2 to center and 1 and 3 to either of the outside poles.
      This should give you 1+2 connected OR 2+3 Connected in either position of the switch.

      Delete
  43. This comment has been removed by the author.

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  44. I've built this with the John Kallas layout. You can definitely hear the difference between 1 and 2 octaves especially with the blend knob to extremes. I also put the output 10 n cap with a switch and it's a drastic bass/treble type of mod. Very good. Adjust to taste.

    Important** I found this circuit operates between approx 5.1 volts input supply and 4 volts. Above that and it just shuts down. John has a 470 ohm resistor in series with the supply to adjust this as he noticed it was too glitchy. I've actually increased that to approx 750 ohms. I've used several 4013 chips so it wasn't a bad IC etc. I also put a voltage starve/sag pot on the supply for approx another 400 ohms. This is the SH*T! It allows for the variable input voltage between approx 5v and 4v depending on your source. You get a massive amount of different fuzz and octave sounds by adjusting this pot. Highly recommend. Enjoy!

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    1. This sounds really interesting... I'll start the build over the weekend hopefully.. tempted to try this with your mod..Can you kindly explain how you connected the sag pot on the supply please as I'm quite inexperienced? I'm not going to use a battery for this box..just AC adapter input.You just place the pot in between the positive connection of the input to the board? I'll probably also increase the resistor on the supply as I'd love to have less fuzz on it...thanks

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    2. Yes you simply need to put a linear pot in between the dc jack + supply to the board. Lugs 1 and 2. I used a 1 k pot with another resistor across lugs to reduce total resistance as I mentioned. Suit to taste. Enjoy.

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  45. Hey everyone. I just finished building the MXR following the John K mod, however I'm having some issues.
    To hear the signal i need to raise the volume of my amp almost to full, with the level of the effect on full already. You can then slightly hear the wet signal but it's kind of chocked. I think there is some effect going on but it's barely perceivable. Any suggestions please?
    I had a bit of problem with the Level 2 connection as on the layout it shows Level 2 being connected to the PCB and then it says level 2 to output. So I connected lug 2 of the level knob to the board as shown and then took another wire from lug 2 and connected it to my bypass switch. Is this correct?
    I would really appreciate any help as soldering and off-board wiring looks fine. I mean, LED is working, true bypass works as well and there seems to be a flow current through the board as well.
    Thanks!

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  46. Put this together with John's layout. Put the 10n output on a toggle for the boost and used 100k for the blend pot. I think it sounds awesome especially on the neck pickup. Close to the mutron octave divider sounds. Thanks John!
    http://img.photobucket.com/albums/v355/tomkogut/IMG_0160_zpsb2cd1825.jpg

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  47. Please help me out someone, I'm having similar issues to other people; effect is very weak, fuzz is audible but dies out nearly straight away, fizzles out like a dying battery. Pots having barely any effect on the sound though I think I can hear the octave effect a little.

    I've triple checked my layout, reflowed all solder joints and checked pin outs of all ic's and still nothing. I'm using a power supply with a constant 8.99v DC output. My blend pot is a linear 100k and level is 50k Lin.

    Here are the voltages on my ic's:

    Ic 1:

    Pin 1: 4.42v
    Pin 2: 4.42v
    Pin 3: 4.13v
    Pin 4: 0.9mv
    Pin 5: 8.99v
    Pin 6: 1.44v
    Pin 7: 4.56v
    Pin 8: 4.35v

    Ic 2:

    Pin 1: 8.99v
    Pin 2: 1mv
    Pin 3: 1.2mv
    Pin 4: 0.8mv
    Pin 5: 0.9mv
    Pin 6: 0.8mv
    Pin 7: 0.8mv
    Pin 8: 9v
    Pin 9: 0v
    Pin 10: 9v
    Pin 11: 9v
    Pin 12:0v
    Pin 13: 9v
    Pin 14: 0.1mv

    Any help is greatly appreciated!

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  48. Is it possible to have a link to the schematic? I guess it's not the tonepad one, right?

    It works ok, but i had to get rid of the 56k* resistor and not use a jumper otherwise I could not obtain a pure synth octave with blend fully CW

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    1. http://www.cjlectronics.com/yahoo_site_admin/assets/images/MXR_Blue_Box.190182925_std.JPG
      +m

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  49. Hope it helps, got to see original paperwork from MXR in stash a buddy bought in Rochester yrs. ago. made mention in early 'studio sounds' I think of using shielded wire on input, output, or both...can't remember exactly, but revision & notation was clear, also about only grounding one end of braid. I always wanted one as a kid, but couldn't afford...when my bro came up on all these boxes of old orig boards, pots, parts, etc. I got one of each, p45, envelope, micro chorus, dyna comp, and boards for a few p45s & envelopes. sooo cool, and seeing orig. schems, and layouts was icing.

    Whenever anyone sits in on my rig, they always ask about it.....'what's that wild distortion' or something to that effect. heck, they'll make a tele belch fire!

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  50. Hi,
    Which one is "C11" on John's Layout please ?
    Cheers

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  51. I just finished my build of John's version. I have a question about the level pot. There is a lead coming from the board that is labeled Level 2 but in the notes it also says Level 2 to output. Is this a double link( board to the pot and then out , on the same lug) Any help would be appreciated.

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  52. I just finished my build of John's version. I have a question about the level pot. There is a lead coming from the board that is labeled Level 2 but in the notes it also says Level 2 to output. Is this a double link( board to the pot and then out , on the same lug) Any help would be appreciated.

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  53. hola... yo hice la version casi original replicando la placa..... y me suena muy suave..... tengo que revisar y si no anda bien repetire todo pero esta version veroboard

    hello ... I did almost original version replicating the plate ..... and it sounds very smooth ..... gotta check and if not right repeat everything but this version veroboard

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  54. Hi gentlemen,

    I'm having a head-scratcher with this. I've got it sounding beastly but mine doesn't seem to have a strong octave, it's definitely there but the fuzz drowns it out, even with the blend all the way off its still not very strong.

    I used an HEF 4013BP could this be the issue?

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