Tuesday, 26 February 2013

Zombie Chorus

Original design by John Hollis, this version has been modified slightly to have a second vbias network specifically for the LFO IC with same value resistors as per Mark Hammer's suggestion in an attempt to solve the ticking problem some people have experienced.

Tweakers may want to add a Chorus/Vibe switch, and if so you can do this by switching out the 10K resistor directly to the left of IC3.

Video of Geiri's build of this layout:




Original version





Modded version with Chorus/Vibe switch





Modded version with Chorus/Vibe switch and 3 speed Mode switch



115 comments:

  1. I'm gonna start working on this one - I love the sound of this thing - Thank You!

    ReplyDelete
  2. You could have done it a week before :P

    ReplyDelete
    Replies
    1. We like to play hard to get sometimes! :o)

      Delete
  3. So that's why it's called 'zombie chorus'! I've never heard any sound clips of this before! I'm not normally a fan of Chorus, but I quite like this though!

    ReplyDelete
    Replies
    1. Yes it seems quite extreme, that's why I think the Vibe switch is a worth while mod.

      Delete
  4. OK, I just fired it up and it's working - nice lush chorus and no ticking! I didn't do the Vibe switch mod but I'm tempted - will this mod alter the chorus sound? Thanks for the nice layout!

    ReplyDelete
    Replies
    1. Now that was fast! Thanks for verifying Frank!
      +m

      Delete
    2. Nice one Frank. In answer to your question, no it won't affect the chorus sound. The chorus effect is just the dry signal mixed in with a modulated signal, whereas the vibe effect is modulated signal only. So the 10K resistor passes the dry signal into the mix just before the output, so if you switch that you are just essentially turning the dry portion on or off.

      Delete
    3. Thanks for the explanation Mark - I know what I'll be doing tomorrow!

      Delete
    4. Great, looking forward to hearing how it turns out

      Delete
  5. Version with Chorus/Vibe switch mod added

    ReplyDelete
  6. Is it possible to have a LED blinking in tempo?

    ReplyDelete
    Replies
    1. I was thinking about that before. You'd need to take a feed from pin 7 of IC4 (or daisy chained off the Rate 3 lug, and I suspect you will still need a resistor of some sort to limit the current. That's where you will want to experiment anyway.

      Delete
  7. I just added the vibe mod switch and that works nicely - it got me to searching for other possible mods, and I came across a mod that Mark Hammer used on his. Here's what he said:

    "My Zombie has a 3-way mode switch on it. Two modes are stock, and the third uses a smaller value cap (330pf or so, I think) to bump the clock frequency into the range normally shared by some flangers when attempting to mimic slow Leslies. So, just a hint of comb filtering. Sounds nice. Reminded me of "Badge" when I first heard it."

    I'd like to add this mod also but I can't find any more info on how to do this - any help would be appreciated.
    Thanks Mark!



    ReplyDelete
    Replies
    1. Sounds cool, you should do it and report back how it sounds.

      Delete
    2. I suspect it will be one of the 1nF caps attached to the Mode switch, but I'm not sure which one. I'll see if I can find more info.

      Delete
    3. Looking at the datasheet for the CD4046 it looks like the 330pF will have to go in between pins 6 and 7 instead of the two 1nF networks that combine in conjunction with the mode switch. I'll have to have a think about the best way to add it with the minimum amount of changes to the stock circuit.

      Delete
    4. Right I messed something up first time so to start again.

      Right I've added a new modded version with a 3 speed Mode switch added. Just to explain it, the caps go between pins 6 and 7 of the CD4046, so you always have the (moved) 1nF cap on the board in circuit.

      The M Sw wires share holes with the middle 500pF cap on the switch. In the middle position the middle 500pF cap is put in series with the 1nF cap on the board giving you 333pF and the slowest speed setting. In the down position the two 500pF caps on the switch are combined in parallel to give you 1nF, and then put in series with the 1nF board cap to give you 500pF which is the middle setting. In the up position all the switch caps are bypassed leaving only the 1nF board cap in circuit giving you the fastest setting.

      The speeds are out of order but it's about as close as you can get using a common 3 position toggle DPDT switch.

      Delete
  8. Vibe switch is interesting. I think that in Sabro's vero is the R5 the one to replace if I'm not wrong. Will try it this weekend (and if so, i'll get rid of a standing resistor :p)

    BR

    ReplyDelete
  9. Wow, I can't thank you enough for posting these mods! I'm gonna see what I can do with that 3 speed mode mod, but it'll have to wait till tomorrow. Not enough hours in the day!

    ReplyDelete
    Replies
    1. There you go Frank try that one, it should be easier to adapt.

      Update for Frank

      I didn't change the type for the mode switch in the notes but it's a DPDT on/off/on

      Delete
    2. Oooops - I already made the adjustments on my original build - it's a complete Frankenstein board now, but it's working as are all the mods. The only problem now is, it is ticking. I don't know if that's due to me moving all the parts around, fixing original trace cuts and adding the new cuts and links etc. I'm gonna try a new build when my order of veroboard arrives - I had to join two pieces together on my first build because I didn't have a big enough piece, but I want to try this again with one board!
      I really want to thank you for all the time and effort that you put into this, and all the other layouts! SUPERB!!!

      Delete
    3. Also, I found this diagram to stop LFO ticking:
      http://tinyurl.com/c66864h
      The gentleman who posted this recommended a 1000uf cap but he used two 470uf caps in parallel because he didn't have the 1000uf cap.

      Do you think this will help with the Zombie Chorus ticking?

      Delete
    4. And in the above LFO De-Tick layout, there is a trace cut beneath D1 - but D1 is optional anyway.

      Delete
    5. In all honesty, if a 470uf cap doesn't do it, then a 1000uF won't either. I don't think it's noise from the power supply, it's LFO noise. It would probably be better to increase both 10u vbias filter caps, particularly the one attached to the LFO rather than the main filter cap. It could be something as simple as a wire that has moved close to a sensitive source during your mods. We know the effect CAN be silent because it used to be, so something has altered which has introduced the ticking and that points to interference from a wire somewhere. Just try moving them about a bit to see if the intensity of the ticking changes?

      Delete
    6. I just want to give you an update on my second Zombie build using your layout with all the mods - everything is working and no ticking with this one! Thanks for the layout, mods and help - I really appreciate it!!!

      Delete
    7. Great, thanks for reporting back Frank

      Delete
  10. What needs to be done to make this bass compatible? :)

    ReplyDelete
    Replies
    1. There isn't that much to change to be honest. Most of the components are dealing with the LFO, clock and BBD and they wouldn't change so really you're just looking at maybe increasing the caps in series with the signal path to make sure all bass frequencies are getting through.

      The most obvious cap that may need changing is the 1nF input cap which to me looked small even for guitar (although it's obviously not by the demos). The output cap at 1u looks ok for bass. Apart from that there are a couple of low pass filters but they'll let all the bass frequencies through anyway.

      So I'd say socket the input cap and see what difference that makes with bass, apart from that everything else would appear to be compatible.

      Delete
    2. Mark,

      Thanks a ton mate. Great job overall. Keep it up!

      Delete
  11. I bought these MN3007's and they worked fine for me. I suppose it'a decent price

    http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=111001427868

    ReplyDelete
    Replies
    1. Ha ha, that's good to know, I bought 20 off them yesterday! :)

      Delete
  12. I have a question on this pedal.
    Will this pedal create the same sounds as a EH Small Clone / Analog man Chorus with a switch to get it sounding like a Roland (boss) CE-2 ???

    I need a good chorus and am interested in this build, or tonepad's Small Clone clone
    lol

    anyone?

    ReplyDelete
    Replies
    1. Try the Small Clone clone (or original, I've seen used units for about 30 euros).

      Zombie Chorus is not an incredible chorus, nor near a top one. Sounds really good, but if you're thinking about a CE-2, forget about it.

      Samll Clone emulation is better, but not verbatim. It's a good chorus, a nice and project, but has its own personality, if you're looking for a SC or a CE-2, go fot them.

      BR

      Delete
    2. Ah ok, I will just go for the Small clone clone then... I really don't care for the CE-2 tones and like the Kurt Cobain warble that you get from a small clone!
      thanks!

      Delete
    3. That surprises me Javi, I've got a Small Clone and it's lack of controls make it a bit of a one trick wonder. I thought the Zombie would have been preferable actually, especially as the important components are pretty much the same or comparable, it's just the clock method that differs.

      Delete

    4. Mark, the Zombie in clone mode is able to sound similar to the SC, but sounds just "similar". If you just play with the Rate Knob, and forget about the depth, you can get some spots where the sound is nearly verbatim, but that's all. The Zombie has not all the sounds of the Small Clone, and what's more interesting, the Small clone has not by far all the sounds of the Zombie.

      To my taste, the Zombie is much more preferable and versatile but won't consider it a Small Clon substitute, as I stated previously, has its own personality.

      Haven't checked the SC circuit (I'd never consider cloning a comercial modern pedal that I can get in nearly mint state for 30 euros), but have red in some webs that the zombie lacks many components that are present in the CE and the SC.

      That's why I recommended to Leo that if what he wants is the SC sound, go and get one (cheap and good sounding), because if he builds the Zombie, may love it o may find that he gets not the sound that he wants.

      By the way, I absoultely recommend building the Zombie if you want to try a versatile and fun Chorus, but woulnd't do it if what you want is a Small Clone.

      BR

      Delete
    5. The Zombie, Small Clone and CE2 are all very similar indeed. Opamp inputs and outputs with the BBD in between. Clock linked to the BBD (CE2 uses MN3101, SC uses CD4047 and the Zombie uses the CD4046) and all with dual opamp LFOs.

      The main difference is that the Small Clone and CE2 has (I think) 4th order filters followed by a buffer at the input and output of the BBD, so there is a bit more component tone shaping to the modulation.

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

      Delete
    7. Well, I installed the vibe switch some minutes ago, as was waiting to some CD4046 that i ordered a few days ago (I used the 74HC4046, that seems to be direct replace).

      Vibe switch: yeah, it's a nice adiction to the Zombie, like the extra versatility it offers to the effect.

      CD4046 was socked when I could hear..... tickin'! Didi install the 74HC4046 again, and problem gone. I've been taking a look to both datasheets and all I could understand is that these ICs are not exactly the same, so not a full replacement.

      Can¡t really find differences in tone using both, just the tick tick problem!

      No need to tell that the original 74HC4046 has returned to the socket. Will have to comment this issue with Harald.

      BR

      Delete
  13. If you have ticking problems, try placing a buffer or a booster in front of the zombie. I got a MXR Microamp, and when it´s on, the ticking disappears completely

    ReplyDelete
  14. Just an observation from me when building my second Zombie Chorus. If you're getting a dry signal coming through but no chorus effect, then you've most likely got a faulty MN3007. I bought 10 of them and 3 didn't work. I recommend testing all the ones you've got and bin the faulty ones.

    I've also built the Little Angel chorus but this thing is just SO MUCH BETTER. It's worth it and it's not really hard to put it in a 1590B anyways.

    ReplyDelete
  15. Hi guys,

    I finished the pedal and works really good, however I noticed that the signal saturates if I use the humbuckers instead of the single coils of my guitar, is that normal?

    Any suggestions?

    ReplyDelete
    Replies
    1. Modulation pedals can often clip with a hotter signal, I had a Jacques Meistersinger which was fantastic but suffered from the same issue when I was using my Les Paul.

      I'll see if I can find a mod to tame it a bit when using humbuckers.

      Delete
    2. Thanks very much for the explanation Mark, I'll stay tuned!

      Delete
    3. Hi,

      jumper the 47K next to the mode switch terminals with a bare wire and remove the 100K that is connected to the 47K. Found this information in a german forum, works fine for me;-). Blinking LED feed from rate lug 3 doesn´t work btw...

      Heiko

      Delete
    4. Hi Heiko,

      Thanks for the mod!, the pedal works a lot better now, however, in the bridge humbucker still a bit of saturation but a lot acceptable than before.

      Delete
  16. Any op amp swaps for the tl062?

    ReplyDelete
    Replies
    1. I've built a few using TL072, works fine!

      Delete
    2. You could try any common dual opamp, but the TL062 is particularly good in LFOs which is why I suggested it here instead of the NE5532 shown in the schematic. It's the low power version of the TL072 and many people have commented that LFO ticking that you can hear with some opamps is reduced or eliminated by using the TL062.

      Delete
    3. Fair enough, I'll try everything I have and see which works! haha.

      Delete
  17. Building my 2nd zombie
    This one with the 2pdt mode switch
    I don't have any 500 pf caps, I have 470 and 560, which would be better
    Also does the led+ off the board do away with the need for a 3pdt switch to control the led
    Thanks
    Ed

    ReplyDelete
  18. Built it, worked fine first try, thanks a lot again for a beautiful project. Really nice sounding chorus, I find it better and more versatile than my Small Clone clone (even with the depth pot mod). My only concern with this one is the depth range. For me could be a bit more. Is there a way to extend it?

    ReplyDelete
  19. mmm, somthing wrong, any idea about compatibily of hef4046bp?

    ReplyDelete
  20. This comment has been removed by the author.

    ReplyDelete
  21. Done! well, I had a chance to directly compare it to my tonepad Boss CE-2 build today and the CE-2 is 10X better, but the zombie isn't bad at all. IMO, the zombie is a lot better than the Little Angel.

    Zombie pic:
    http://johnkvintageguitars.homestead.com/Effects/others/Zombie-01.jpg

    Tonepad CE-2:

    http://johnkvintageguitars.homestead.com/Effects/others/CE-2-01.jpg

    ReplyDelete
    Replies
    1. Nicely done John, thanks for the pic

      Delete
  22. Hi Mark, where would I connect the negative side of the LED? Thanks in advance.

    ReplyDelete
  23. the cd4046 must be unbufferet?
    Something wrong and dont found, my cd4046be dont works?

    ReplyDelete
  24. Hi,

    Have any of you guys experienced high pitch noise when mode sw is in off mode and vibe sw is on?
    I have that problem, can someone provide some solution or why does that happens?
    Also my pedal is too noisy...it is humming loudly...on battery not on ps. how to fix that? I use tl72 ics.

    i do have chorus effect it is very very nice but pedal is not working all the way as it should, please can someone help me on this one?

    Thanks,

    ReplyDelete
  25. Replies
    1. mine doesn't tick, but after building a Boss CE-2, IMO, the Zombie is a bit disappointing.

      Delete
    2. I just printed off the Boss. I did notice that the ticking isn't as prominent after swapping the 10uf cap for a 22uf.

      Delete
  26. Thanks Ivlark this was a great build. Spent my time and got it right first time and is sounding great.

    ReplyDelete
  27. hi all.
    happy new merry year holiday xmas -can't spell hanika.
    is a CD4046BE ok to use here. The pix show CD4046 (no suffix). I cannot find a data sheet for CD4046 (no suffix) they are all BE UBE etc...I think BE is 'buffered'...anyway will CD4046BE work?

    ReplyDelete
  28. here's my build (alcohol-driven angle!) of the Zombie Chorus, w/vibe &3pos mode switch.
    http://imageshack.us/a/img19/5792/eey1.jpg

    i quite like it, but it's definitely noisy (less noisy with switch in the middle position)

    ReplyDelete
  29. What kind of noise? Hum, hiss? I built this a while back and mine is very quiet. Now, I will say that I haven't played it at stage volume but I've had it at mid volume level and never noticed any noise. Have you tried a different power supply? I use a 1Spot and have never had any noise issues from power supplies. But I have read back on different threads where noise issues were improved or eliminated with different/better regulated power supplies. Just a thought.

    I do like this chorus. I hadn't played it for several months and plugged it in during the holidays when I had more spare time. You can cover a lot of sonic ground with the mode and vibe switches. Knocked my Boss Chorus ensemble off the board ( I had used the chorus ensemble for the last 15 years or so...).

    ReplyDelete
    Replies
    1. If the banished CE is a CE2, I'm more than willing to offer a new home to this little pedal:P

      Delete
    2. here's a soundclip i've recorded with bass, so you can judge by yourself:
      http://clients.cylens.net:8117/diy/zombi_chorus_vibe.mp3
      same when powering with a brand new battery and swapping ICs...

      Delete
    3. Javi

      Afraid it's just a normal CE5 - really does a great stereo sound though with 2 amps. Sabro's got a verified CE2 layout though. I think you need to build it and squeeze it into an A enclosure ;). http://www.sabrotone.com/?attachment_id=3738

      cylens - it seemed pretty quiet ( except for the switch popping ) up until about 2:44. Then I hear the hiss. Wonder if that setting that you change to there has a little more gain on the circuit. I'm not technically able to ascertain that with my knowledge level though. Nice tone and playing btw....adds a nice swampy texture to your already nice tone.

      Delete
    4. around 2:00 I put it in "vibe" mode, si I guess the noise coming from the delayed signal is more exposed (not mixed with dry signal).

      don't get me wrong, i'm not complaining and will definitely use it, but to me, this is not "clean": the bass goes straight in the audio interface so it clearly exhibits the characteristics of the pedal (i wouldn't say "flaws"). should i have plugged it in an amp, I might not have bothered... thanks for the kind words!

      Delete
  30. I'm quite new to veroboards, but there seems something strange with the layout:
    what's the polarity of the 1uf cap (between output and VSw5)

    It could be my stupidity of course

    ReplyDelete
  31. I'm quite new to veroboards, but there seems something strange with the layout:
    what's the polarity of the 1uf cap (between output and VSw5)

    It could be my stupidity of course

    ReplyDelete
    Replies
    1. It shows a polyester capacitor which don't have polarity

      Delete
  32. Ah ok, didn't know that existed even. Is there an audible difference in between the polyester cap and the electrolytic for 1uf?
    Is there also a possibility to make requests for certain effects?
    Thanks for the fast answer and the great job being done here!
    Cheers

    ReplyDelete
  33. I built this 2 weeks ago and still can't get it going...I have tried everything. I even cut and repopulated a new board. I'm getting nothing but dry out of it.Tried 4 different MN3007, 3 separate CD4046, and 2 sets of TL072 chips. I've checked all cap polarity's and triple checked all ohm values. All jumpers and cuts are correct and i still can't get it going. Any one have working voltages on the ICs? Please help?!

    ReplyDelete
    Replies
    1. Oddly enough, I too am having the exact some problems. Unfortunately, the MN is 10.00 and I'm not real happy about dropping 50 or 60 bucks just to get one to work.
      I know - the bay has them cheaper I'm sure, I really prefer not to go that route. So - I'm shelving this one as I did with the 2 builds of the Angel chorus. I guess modulating devices are just not my types of builds *sigh*

      Delete
    2. You may prefer not to get them from eBay but sure it makes more sense to put the board to one side for a while, get some and then see how you get on when they arrive. I've bought a few of these and they work fine, at that sort of price it's a no brainer when the alternative is ditching the board http://www.ebay.com/itm/271376214280

      Delete
  34. Hi everyone,
    I just finished this layout (with vibe switch and 3 speed switch) and have (too) many problems.
    First, I only have dry signal. I tried another MN3007 but it sounds exactly the same.
    So 3 speed switch logically doesn't make any difference.
    Though, I can hear a ticking noise.
    And a last problem with the vibe switch: I only have signal in one of its two modes, when 10k resistor is on.
    Any help, please?

    ReplyDelete
    Replies
    1. I forgot to say I tried other dual opamps. Same result. :-(

      Delete
    2. When the 10K resistor is in circuit, it passes the dry signal and so you get a chorus effect with dry signal and modulating signal mixed in with it. In Vibe mode the 10K resistor breaks the dry signal and so you only get the modulating effect, hence a vibe. So if you're only getting sound when in chorus mode it sounds like you're just getting dry signal and you're not getting the modulation from the MN3007.

      You're getting ticking so the oscillator is working (although the speed switch should change the rate of the ticking). So to me it sounds like the MN3007 or some of the connections to it. Are you sure they are ok? There are a lot of fakes out there for MN series ICs and you may have a entire bad batch.

      If you do know the MN3007 is good, then check the pin voltages to see if that throws up any clues.

      Delete
    3. Thanks for your help and your explanations, Mark!
      I'm not really sure my 2 MN3007 are good: they are the 2 first I have, so I can't put them in another build to verify they work.
      And even if I bought them on a renowned site (not ebay...), I don't know if each IC is checked by the seller.

      So I checked the pin voltages.

      For a DC input of 9,71v (AC adapter):
      Pin 1: 9,71v
      Pin 2: 4,71v
      Pin 3: 0,10v
      Pin 4: 0v
      Pin 5: 0v
      Pin 6: 4,80v
      Pin 7: 4,90v
      Pin 8: 4,90v

      What can you tell me about these results?
      Thanks again! ;-)

      Delete
    4. Mine is working with these voltages:
      Battery at ~9,2V
      1: 9,0
      2: 4,48
      3: 4,90
      4: 0
      5: 0
      6: 4,5
      7: 4,97
      8: 4,97

      Your measurements seem to be in the ballpark, so i think you're problem must be somewhere else than with the 3007.

      I do find this to be ok chorus, but it has real difficulty taking hot humbuckers in without adding distortion. Should probably try to lower the mixer gain at some point. Works ok with singles.
      +m

      Delete
  35. Hi Mirosol and thanks for sharing your voltages!
    The only difference I can see when I compare them to mine is about pin 3: my voltage is weak for the least. Does it mean that signal doesn't come to 3007?

    ReplyDelete
    Replies
    1. Hi everyone!
      Good news: my Zombie Chorus works like a charm!
      My problem was a faulty socket on IC1...
      And there's no ticking anymore. Great!

      Thanks to Mark for this great layout (again) and your help with Mirosol!

      Delete
  36. I think i have a crude workaround for the distortion. I soldered 4K7 in parallel with the 47K from IC3 pin 2 to IC1 pin 3. At least it tamed most of the distortion while keeping the level up. I think this sounds even slightly softer now. If not softer, then slightly less harsh. It still distorts when i hit chords hard, but not nearly as much as before.

    So if someone else is experiencing the same issue (distortion with good humbuckers), just lower the value of that one resistor.
    +m

    ReplyDelete
  37. Just finished up my 2 nd zombie
    Gave the first to my son
    This one sounds nice and clean with no ticking
    However the depth knob O's not functioning
    The chorus seems fixed at about 50 %
    Any suggestions on de bugging this
    Thanks
    Ed

    ReplyDelete
    Replies
    1. Check the voltages of IC2 and IC4 and let us know what you get

      Delete
  38. i just built this but it real tame..doesnt wobble like the demo video nor does it really sound like a chorus. any idea what could be wrong?

    ReplyDelete
  39. Is the MN3207 a substitute for the MN3007? Specs seems to be the same and it's much cheaper.

    ReplyDelete
    Replies
    1. They do the same thing but you cannot replace one for the other in a circuit without modification, so no you'll need to use the MN3007 in this.

      Delete
  40. hmm... Okay thanks Mark.
    I will check on Ebay for more friendly priced ones. Inet shop here sells them for 12 euros each.

    ReplyDelete
  41. I confirm, if it doesn't work, try many MN3007...I've bought 5 of these on ebay, 3 doesn't work, 2 works but maybe not very very well I think............

    ReplyDelete
  42. These are cheap enough to buy in a few and I know at least some are good because I've had them before and so has Javi I think

    http://www.ebay.com/itm/271376214280

    ReplyDelete
  43. Ig I'm not wrong, these are the ones I purchased time ago:

    http://www.ebay.es/itm/2pcs-Panasonic-MN3007-Audio-AMP-Delay-Effect-IC-m-/170690231721?pt=AU_B_I_Electrical_Test_Equipment&hash=item27bdee3da9

    No problem so far, al I've used, worked great. Anyway, when I need a genuine IC beyond any doubt, I purchase it at Retroamplis, a spanish based store, but prices are not exactly cheap :P

    http://www.retroamplis.com/epages/62070367.sf/es_ES/?ObjectID=3582809&ViewAction=ViewProduct

    J.

    ReplyDelete
    Replies
    1. That's still a great price if you know they are guaranteed to be original and working well.

      Delete
    2. Here's one for you mate
      http://www.retroamplis.com/epages/62070367.sf/es_ES/?ObjectPath=/Shops/62070367/Products/%22TR-MATCH/2N5952-4%22

      :o)

      Delete
    3. Hehehehehehhe, I didi see this quad, but as I wanted too some vactrols, I did purchase both quad and vactrols at Musikding. Optos were way cheaper.

      Have to build still the Phase 90, is still on my to do list :P

      Delete
    4. I bought my MN3007's from BanzaiMusic and got my Zombie walking :)

      Firstly I tried a couple of 3007's bought from eBay, but they seemed to be bogus. I had clean signal coming through but no effect of any kind.
      I bought two 3007's from BM and to my relief, they actually worked! And I must say, this pedal is a gem! Worth every penny and hours of troubleshooting :)

      Thanks, Mark!

      Delete
  44. Hi, I have the same problem as other builder...My build makes a siren noise in one of the modes, If I place the Zombie behind something else, tuner or compressor the sound vanishes, also if I cut the tone of my bass... any ideas about this?

    ReplyDelete
  45. I just finished building the vib mod version of this layout. Overall it is working fine.
    However I have a weird ticking problem. When I test the effect with my bass, an
    Ibanez active bass, everything works fine. However, when I used it my guitar, a Cort
    statocaster look-alike, i get ticking even if the effect is bypassed. I sued the following wiring scheme for the 3PDT foot-switch:
    http://www.singlecoil.com/tb-strip/dia1.html
    Is there anything I could try to solve this issue?
    P.S. I made the ground connection of the jacks and the foot-switch from the board instead of from the DC jack, could this have an effect on the ticking?
    thanks a lot.

    ReplyDelete
  46. i have a problem with mine, i have build this model of zombie chorus and i just have like a feedback distortion when i play very loud my big string on my bass and that, just for a little time. I check out all the circuit and i didn't found anything wrong. And i don't know if is wierd but when i check the source voltage with my battery when all is plug (in and out jack), the voltage always go down slowly, like ,01V by sec. Thank you

    ReplyDelete
  47. Hi Mark!. I like so much your web, is great. Well... I'm working in the Zombie Chorus original version, but I didn't find a 1uF polyester/ceramic capacitor, then I decided to bought one electrolytic, but I don't know how to connect it, in which position I've got to put it on?, negative or positive to output? Thanks a lot!!

    ReplyDelete
    Replies
    1. You should put the capacitor so that the negative goes to output.

      Delete
    2. this is no good aki. you'll lose half of your waveform that way considering the polarized cap would filter away the negative part of your signal.

      Delete
    3. This was a year ago and I'm sure he got it sorted, but for the benefit of anyone reading this as they build.......That's not how it works. Capacitors, polarised or not, pass AC (guitar signal) just fine. Just look at any fuzz face schematic. Its the frequency content they affect. Larger value = more bass. You can use a polarised cap in any place where the voltage on one side (positive leg) is always higher than the other side (negative leg). Or make a non polarised cap by placing 2 polarised caps in series back to back.

      Delete
  48. hi i need help on this one ! i just finished it and it works great but i get some hissing and the ticking, i did the original project, i need THIS schematic please, with the second vbias network specifically for the LFO IC, also i used tl072 instead of 062 and linear pots instead of log, coud that be the issue. someone help please !!

    ReplyDelete
  49. Here's another little demo: https://youtu.be/hSUPPEuxgPE

    ReplyDelete
  50. Hi there! This is definetely a good one. However I think it´s cutting some treble. Is there some kind of lowpass filter cap to replace?
    thanks!

    ReplyDelete
  51. Anyone figure out how to have a blinking RATE LED?

    ReplyDelete
  52. Hi all, I managed to get clean sound through, no effect at all...

    here are the voltage reading for the ICs.

    IC 1
    8.9
    6.6
    5.07
    0
    0.1
    8.9
    8.86
    8.88

    IC 2
    6.61
    6.61
    8.9
    8.9
    0
    6.94
    6.95
    0
    4.56
    8.08
    0
    0
    6.42
    8.91
    8.33
    8.9

    IC3
    5.08
    5.01
    2.5
    0
    8.71
    7.61
    7.61
    8.9

    IC 4
    4.48-5.3 (unstable reading)
    4.6
    4.5
    0
    4.3-5.3
    3.4-5.5
    8.9

    I notice that pins 6-8 of IC 1 are different from the voltages posted here.

    Also, for the LED+ wire, I just connect it to the anode of a RED LED and the other end connects to ground. It's on constantly as long as DC jack is plugged, is this right?

    Any advise would be very much appreciated, Cheers!

    ReplyDelete
  53. This comment has been removed by the author.

    ReplyDelete
  54. Dear guys, diyers and all of you :)
    First thanks you for sharing your knowledge and projects, I appreciate it.
    Second, I've been working on 3 of this zombie chours, all done on Mod 2 layout (vibe sw + mod sw).
    The good news it's that all of them work pretty good, very nice sound and versatile usability.
    The really bad news it's that all of them have ticking issues! :(
    I've spent a lot of time on the problem without obtain nothing so i decided to write to you :)

    I've made many experiments, here the tests and the responses
    WITHOUT CHANGING ELECTRICAL COMPONENTS
    1) Using an active pick-up guitar => ticking got muted, just a bit of hum, but it's ok!
    2) prepending a buffered pedal (Boss like) => ticking got muted and a bit of hum

    CHANGING ELECTRICAL COMPONENTS
    1) tried TL062 vs TL072 = always ticking
    2) changed MN3007 and CD4046 (may faulty but..) = always ticking
    3) changed caps = always ticking

    QUESTIONS:
    1) could be a grounding problem?
    2) coloud be a component problem (type of capacitor..etc)
    how to solve or get an hint?

    Thanks in advance to everyone
    Luca :P

    ReplyDelete