by gaussmarkov

Gristleizer Layout

In this project, Chris (stobiepole) and I have put together PCB and vero layouts for the legendary Gristleizer by Roy Gwinn and popularized by Chris Carter and the Throbbing Gristle. We have verified both and have found no ticking problems in our builds from the LFO. We are planning to use this as a starting point into some new territory with this kind of noise maker.

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49 Responses to “Gristleizer”

  1. Chris said:

    You could replace the trimpots (except for the bias) with external pots for even more wacky sounds.

    Using the MAX1044 power circuit makes biasing the Gristleizer much easier – you should be able to leave the trim pot set at the mid-point.

    Future plans for this one include adding a CV input, so that an external LFO can be used to drive the filter.

    Posted 24.08.2007 at 6:27 pm

  2. Audioguy said:

    wow this one looks cool. I dont suppose you would have a part number for the rotary knob????

    Posted 28.08.2007 at 8:59 am

  3. gaussmarkov said: and both have some relatively cheap 3-pole 4-position rotary switches. I’ve never seen 2-pole switches except with more positions so I would just leave the third pole unused.

    Posted 28.08.2007 at 11:41 am

  4. certain_ant said:

    I’m building one of these on protoboard.
    Your connections to SW2 B1 and B4 are
    swapped on the layout. I’ve used schottkies instead of the Ge diodes – no problems. From IC1 pin 6 I have another
    transistor rigged as a follower with a LED plus load in its collector to +9V and its emitter grounded. 6k8 between its base and IC1 pin 6. This gives a flashing indication of the rate. Crude but maybe useful.
    I’m going to use this thing in a modular synth so I’ve got +/- 12V. I’ve used three terminal regulators to get the 9V rails. Maybe not needed. Perhaps you can just increase R7, R8 a bit?

    Posted 15.09.2007 at 6:08 am

  5. certain_ant said:

    Oh and another point. C7 is a bit low isn’t it. With R19, you get a time constant of 4.7ms => 200Hz. I’d
    increase it to 1uF since non polarized 1uF aren’t that expensive or enormous any more. Is there anything to be gained at the top end by using better op-amps for IC4 and IC5?

    Posted 15.09.2007 at 6:20 am

  6. certain_ant said:

    And another. Chris said “replace the trimpots (except for the bias) with external pots”. If you look at Chris Carter’s note at
    the ‘bias’ is the one trimpot he does bring out on the case. Haven’t tried it myself yet.

    Posted 15.09.2007 at 6:28 am

  7. gaussmarkov said:

    Hey certain_ant! Thanks for all the useful comments. I will fix that hook up error.

    Honestly, i don’t understand the circuit well enough to know whether changing R7/R8 is enough to account for increasing the supply to +/- 12V.

    Regarding C7, that’s not an unusual choice for guitar effects but I can see that you might want to increase it. And while you are messing with the input, you might want to increase the input impedance as well. For electric guitars, 47K is pretty low.

    As far as IC4/IC5 go, I think you would hear the difference upgrading those op amps. Whether it’s preferred or not is probably going to be a matter of taste.

    The LED indicator and trimpot thoughts are money. Thanks again!

    Posted 15.09.2007 at 7:45 am

  8. gaussmarkov said:

    The hook ups to SW2 have been fixed. Thanks again to certain_ant! 🙂

    Posted 16.09.2007 at 1:28 pm

  9. certain_ant said:

    Thanks for the prompt response!

    Looking at the datasheet, TR1 2n3906 will take 40V collector-emitter and max 200mA collector, so I don’t think it will blow up even if you took the rails to +/-15V. Tr2 might hit a problem though. I read its datasheet and didn’t understand what the limits were! Maybe I’m better off with the three-terminal regulators.

    Regarding IC4 input, you could take R19 to 470k – which would give your high impedance and my low freq response. However, I seem to remember that 741s get upset if the input resistors are greater than the feedback resistor. So maybe consider replacing IC1 with something more recent rigged as a low-noise, high impedance x10 buffer.

    However, as you say its a matter of taste and this unit obviously isn’t meant to give ‘hifi’ reproduction anyway.

    Posted 17.09.2007 at 4:38 am

  10. gaussmarkov said:

    Hi again!

    I would say that TR2 can be any JFET you like. So that should not stand in the way.

    And, because you mention it, it now occurs to me that I have frequently seen the 741 with a 1M bias resistor. I am willing to bet that increasing R19 to 1M, along with increasing R21 to 1M and R20 to 100K, will be just fine. And, as you say, there is nothing lost in making an upgrade either.


    Posted 17.09.2007 at 4:51 pm

  11. certain_ant said:

    Ok. I can confirm that it runs off +/- 12 V just as well as the original +/- 9V without damage. Looking at the envelope waveforms it produces, there isn’t much difference between the rising triangle, the falling triangle and the equilateral triangle. Listening with synth modules as input, they sound pretty similar too, except maybe at the lowest LFO frequencies. Are others finding that? If true, you might as well drop the rotary switch and have only the square and equilateral positions swiched by a 2-pole-2-way toggle. It would save a bit of cash. Yes, having the bias brought out as a control is good, but none of the other presets do anything interesting enough to the sound to be worth bringing out to knobs.

    Posted 17.10.2007 at 11:55 am

  12. gaussmarkov said:

    Thanks for the build report. Maybe Chris will pipe in about his build. He does not have an oscilloscope, but his ears should be enough. 😉

    Posted 18.10.2007 at 12:18 pm

  13. Roy said:

    The design is very much a product of the seventies. Modern opamps would undoubtedly be better. Ditto diodes – any old diode is fine. Clicks, if you get them, will be a layout issue. The momentary current discharging the integrator cap is large and you should be careful where it goes.

    Rising ramp, falling ramp and triangle should all sound very different. If they don’t, something is wrong.

    The input impedance is way too low – an error in the design. It should be at least 1M for a magnetic pickup. Modern opamps help here.

    Roy Gwinn

    Posted 25.10.2007 at 11:44 am

  14. gigelmargel said:

    i build one, but i can’t obtain 0V at the output of IC3 using the offset trimpot…also i have some problems using the bias trimpot…it sound very distorsed on some settings…on the 3 position of the 4 pole switch i have a big volume drop…can anyone help me with some certain tensions to verify my build?

    best regards!

    Posted 26.12.2007 at 1:36 pm

  15. gaussmarkov said:

    I see that you have gone to Aron’s forum for help. Perfect! 😉

    Posted 29.12.2007 at 9:01 am

  16. Glacial Communications » Blog Archive » Progress report – 10/20/2008 said:

    […] good enough for me), as well as some other soldering gear and a couple of vero/stripboards ( gristleizer, here I […]

    Posted 20.10.2008 at 7:36 am

  17. josh said:

    hey,awesome site. please excuse the simple question, i don’t understand why there is a +9v and a -9v connection to the board. how does this connect to the battery and the offboard components? thanks.

    Posted 27.11.2008 at 9:43 pm

  18. gaussmarkov said:


    you need two 9v battteries for this one. ground is at the junction between the + terminal of one battery (#1) and the – terminal of the other (#2). then -9v is on the – terminal of battery #1 and +9v is on the + terminal of battery #2.

    all the best, paul

    Posted 28.11.2008 at 6:40 am

  19. Chris Grier said:

    About the pots: should they be log or linear? I’m about to go shopping.

    Posted 21.01.2009 at 10:48 am

  20. CHIP FLYNN said:


    Posted 07.02.2009 at 8:41 pm

  21. francesco said:

    hello, I have built the circuit today, I created the pcb (no veroboard) welded components and all connected but when I link an instrument not get any output signal except a strong buzz …

    Can you help me please?

    Posted 19.02.2009 at 10:37 am

  22. francesco said:

    Hi I’ve finally build my gristleizer for fun, make the pcb (no veroboard)
    soldered all component and pot/sw/….
    but not working….

    when sw1 is in OFF the signal in INPUT don’t go in OUTPUT
    when the switch is set ON the only thing you hear is a low whistle, which can vary by operating potentiometer ‘SPEED’, by varying the sw2 nothing happens also varying the other knobs. the volume works.

    have a list of check to do?
    I need a help! 🙂

    Posted 21.02.2009 at 5:02 am

  23. gaussmarkov said:

    Dear francesco, is not set up for debugging help. The best place for that is That is where I always go. 🙂

    Good luck!

    Posted 21.02.2009 at 6:50 am

  24. francesco said:

    Hi Gauss, tnx for reply
    on diystompboxes i never find the gristlizer….

    Posted 22.02.2009 at 1:11 am

  25. CHIP FLYNN said:


    Posted 24.02.2009 at 1:57 pm

  26. anon said:

    dude, the pcb layout has been verified.

    Posted 24.02.2009 at 3:00 pm

  27. Francesco said:

    I try to check back next week, when I have more time.

    if you find a solution write to me at

    Posted 25.02.2009 at 3:28 am

  28. Glacial Communications » Blog Archive » Monthly DIY project update post said:

    […] received the Gristleizer PCBs I ordered in January. Put one together, but it’s not quite right yet. Waiting to get my […]

    Posted 02.03.2009 at 3:22 pm

  29. Matthew said:

    here is a switch that should do the trick. it indexes to give you a choice of positions.

    mouser 105-SR2612F-26-21RN

    has this project/pcb been verified yet?

    Posted 09.04.2009 at 3:43 pm

  30. francesco said:

    I have not found a solution, but
    I noticed that my dealer gave me like 4 ua741cn and 1 ua741cp instead lm71

    fit the same?

    Posted 12.05.2009 at 1:57 pm

  31. a secret admirer said:

    Sorry if this has been covered:

    On the first page of the pdf, the rotary switch is still messed up. It shows switch A4 connecting to switch B4. Switch A4 connects to switch B1 and to the A4/B1 pad on the pcb. Switch B4 connects to the mis-marked B1 pad on the pcb (second from top left).

    Also, if you use a single inline trim pot, the pad for the center pin on the offset trim is not connected to anything.

    Posted 12.05.2009 at 3:11 pm

  32. Francesco said:

    The connection diagram is wrong?

    Posted 14.05.2009 at 4:51 am

  33. a secret admirer said:

    Yes. A crude correction:

    Thanks for your project!

    Posted 15.05.2009 at 3:00 pm

  34. Glacial Communications » Blog Archive » Busy building things said:

    […] the Gristleizer is starting to get Gristle-y. Somebody pointed out an error in the layout diagram that when fixed, made things somewhat happier. I’m not sure if it’s perfect yet, but it […]

    Posted 16.05.2009 at 12:49 am

  35. Chris Gregory said:

    The PDF might be out of date. Check the layout image linked at the right side of the page for the latest version, which should have the correct details…I’ll look at my own build again to be sure.


    Posted 24.05.2009 at 8:30 pm

  36. Francesco said:

    ok…I made the changes under the new scheme ..
    still does not work.

    I hear the clean sound but when I press the button does not feel anything.

    Posted 01.06.2009 at 11:35 am

  37. greezus croat said:

    um, I could be wrong here, but isn’t the shape setter supposed to be a dp4w switch rather than a pot? I haven’t built one yet, maybe i’m looking at it wrong.

    Posted 09.03.2010 at 8:31 pm

  38. JohnS said:

    Have built the Gristlizer on a home etched PCB. Installed the bigger resistors around IC4 as above and increased C7 to 0.47 mF. The VCF appears to work (I can here it ‘tunnelling’) when I flip it over but nothing much from the VCA setting. Am going to change the resistors back as per original design and try that.
    Also can you check the FET on the layout ? I reckon the ‘flat’ is facing the wrong way. Thanks for design etc.

    Posted 04.05.2010 at 6:42 am

  39. JohnS said:

    Hmmm, wasn’t the impedance mods causing the problems. Still trying to bring it to life, got the scope out now !!

    Posted 06.05.2010 at 5:13 am

  40. JohnS said:

    Changed my mind about the orientation of the FET also. My book says one way but the web says the reverse (several times). Have gone back to position in layout. Have now got waveforms on all 741 outputs so nearly there.

    Posted 11.05.2010 at 4:38 am

  41. Dino T said:

    I’m an electronics newbie (though I’m trying). What are the voltage values for the capacitors? Other than the can caps, do they have to be box or chicklets, or can they be axial (like a pregnant resistor)?


    Posted 01.10.2010 at 8:50 am

  42. sammie said:

    hello there i am very interested in building one for myself, but don’t have the means to print a board. could anyone help me with this. I am In the UK just for reference.

    many thanks

    Posted 04.10.2010 at 4:51 pm

  43. Anonymous said:

    I wouldn’t bother just yet. It doesn’t perform. There is a fundamental issue with the circuit somewhere. I will be working on it soon to sort it out. Been busy this last few months. Somebody on this site knows what it is, but isn’t saying.

    Posted 15.11.2010 at 3:46 pm

  44. jean bender said:

    Hi !
    I’ve just built my kit from smashing guitar, but it seems that i have the same problems as Gigel Margel who wrote here.
    Well, could somebody give me a link to the aron forum which talk about the gristleizer ? I can’t find it anywhere…
    thanks for the help !

    Posted 29.12.2010 at 4:53 pm

  45. Jacob said:

    How do i replace the two nine volts with a nine volt power adapter?

    Posted 02.01.2011 at 11:23 am

  46. Pdr said:

    I believe you can replace the two nine volts using this:

    Posted 04.02.2011 at 3:55 pm

  47. jacob said:

    thank you.

    Posted 06.02.2011 at 1:08 pm

  48. bob said:

    Just built this one on vero (based on the layout in the project PDF, but with the bias and level trimmers taken offboard and a few other tweaks). Works fairly well, but there is noticable oscillator ticking bleeding through to the audio. Roy (Mr. Gwinn, I presume) above says that the integrator cap is a likely suspect, pardon my ignorance, but which cap is that? My wiring could be a bit tidier, so I’ll tackle that first.

    There’s not a massive difference between the 4 waveforms (it is possible to tell which is which, but it is subtle, especially at higher speeds), not sure if that’s as it should be. Also there is a big loss of mid and lower freqs in filter mode, making it sound pretty shrill and unpleasant. VCA mode sounds much better in this regard, with a guitar signal sounding nicely rounded. Would be good to hear from someone else who’s had a go on vero (I can’t be doing with those nasty etching chemicals – RoHS vero rules!).

    BTW – would be nice if Gus were to update the project PDF with the corrected DP4W switch wiring. Took me quite a while to debug.

    With a bit more work, I can see this being pretty great – so a big thanks to Roy Gwinn for designing and sharing this, and to Gus for promoting it to us DIYers.

    Posted 19.02.2011 at 1:19 pm

  49. Jules said:

    I’ve completed my Gristleizer Kit from EA, but It will not power up. I’m a novice builder, wondering where I’m most likely to make a mistake in this build.

    I’m sure it’s something simple, where are faults most likely to occur?

    thanks very much! I enjoyed this build!


    Posted 06.12.2011 at 10:47 pm