by gaussmarkov

Thor Layout

Designed by! I did this one after helping to debug a layout by Xavier on the forum. Thanks to Will Cote for pointing out a component value error. Stobiepole built the prototype pictured above. Runoffgroove says

The legendary Marshall 100W Super Lead adapted for use as a distortion stompbox. Successor to the Thunderchief project. Schematic and PCB layout.

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23 Responses to “Thor”

  1. GCollier said:

    Any thoughts on using the THOR as a solid state preamp. If this were done could you simply incorporate tone controls before the opamp?


    Posted 17.12.2007 at 8:26 am

  2. gaussmarkov said:

    If I were going to add additional tone controls, I would try a passive tone stack after the final op-amp and use the available op-amp in the TL072 in a recovery stage before the output.

    How does that sound? ๐Ÿ˜‰

    Posted 17.12.2007 at 9:51 am

  3. GCollier said:

    Sounds reasonable…

    I’ll see what I can do with my existing Thor. I built it a while ago using the layout at Runoffgroove. Too bad because I could have simply modified your Eagle layout and added the tone stack. I might just add an active EQ after it and see how it sounds.

    Do you suppose there would be an advantage converting this to run on a split supply?

    Posted 18.12.2007 at 1:04 pm

  4. gaussmarkov said:

    Perhaps, but I don’t know what the advantage would be. ๐Ÿ™‚

    Posted 19.12.2007 at 1:02 am

  5. GCollier said:

    I took your eagle file and modified it to use the 2nd half of the opamp as an active 3 band tone control with a swithc to bypass it…built it and it sounds great. Just one issue…the gain control doesn’t seem to do much of anything regardless of how I bias the thing. Could this be an issue from running at a higher voltage (~13.5V). I double checked the pot wiring and continuity in the wiring…any suggestions?

    thanks for the nice layout

    Posted 04.03.2008 at 6:00 am

  6. gaussmarkov said:


    I’m glad to hear that you have made the Thor layout “your own.” ๐Ÿ™‚

    My quick reaction is that, yes, the supply voltage can make a difference and that you could try a lower supply to check that theory. To really diagnose the problem, one needs to know the voltage readings on all of the transistors’ pins when the input is grounded.

    If you post on Aron’s forum about this, please let me know with a pm (personal message) and I will try to help there.

    All the best, Paul

    Posted 04.03.2008 at 6:47 am

  7. GCollier said:

    Just an update to let you know that I managed to solve my issues. I initially dropped the voltage down to 9V but still had the same issues with the gain…in the end it turned out to be a bad pot! Sounds fantastic, the active tone control is a BIG help.

    Thanks for providing such a great layout to modify…so many sites just provide PDF files, the Eagle files are very useful!

    Posted 12.04.2008 at 7:14 am

  8. gaussmarkov said:


    thanks very much for following up! it helps us all. are you going to post your version somewhere? i would be pleased to put it up here.

    and i am pleased that you are benefiting from the eagle files. that is one of my goals.

    all the best, paul

    Posted 12.04.2008 at 8:27 am

  9. thomarz said:

    I’ve just finished my second version of the Thor, this time with the pcb layout of this site. The first one was the one from ROG. Still both cause the same problem. Playing it in front of clean solid state amp at higher gain setting, you get some oszillating sound like a bezerk synthesizer. Sounds really funny but it’s not quite what I was after.
    I’ve sucessfully built some other pedals but this one is really making me go crazy. Would be nice, if I could get some help here.

    Posted 13.04.2008 at 3:59 am

  10. gaussmarkov said:


    It probably isn’t the solid state amp. I suggest you start debugging by listening to each stage of the circuit with an audio probe.

    All the best, Paul

    Posted 13.04.2008 at 6:47 am

  11. gaussmarkov: diy fx » G. Collier’s RunOffGroove Thor said:

    […] part on projects. George Collier took the Thor circuit from, the Eagle files from, and put in his own 3 band active tone control. Here’s a gut shot of his build.ย  If you view […]

    Posted 30.05.2008 at 8:08 am

  12. Nicko said:

    Hi Gauss! I’ve built ROG’s Thor using your layout since ROG’s takes more space in a 1590 box. I would just like to ask why does it sound not the same as the one posted by ROG? As I strum my guitar, the sound that’s coming out of my amp lasts in a matter of seconds like 2 to 3 seconds only. Sustain is worse than I expected. There’s a sparkling noise at the latter part of the sound that’s much similar to one type of fire crackers. I even used both TL072 and TL071 ICs. Hope you can help me out. Thanks!

    Posted 16.03.2009 at 10:49 pm

  13. gaussmarkov said:

    Hi Nicko,

    It sounds like you think the layout is the issue, but that isn’t likely. Others have used this layout with success. More than likely there is a bias problem somewhere.

    If you are unsure about the voltage levels, I suggest you ask the friendly people on Aron’s My site isn’t really setup for debugging.

    All the best, gaussmarkov

    Posted 17.03.2009 at 4:40 am

  14. Rob Schneider said:

    Just wondering if you got GColliers layout with the added tonestack? I would love to add a tonestack to my Thor.

    Posted 13.10.2009 at 9:30 am

  15. robb said:

    i was wondering the same thing about the tone stack. i would be very interested in that also and seemed like a like was going to be put in or something, but nothing i could find. maybe at diystomp?? what gives??

    Posted 23.02.2010 at 10:44 pm

  16. robb said:

    forget the above…i had to dig but here are the links:

    project file –

    G. Collierโ€™s RunOffGroove Thor –

    Posted 24.02.2010 at 12:04 am

  17. Dr Robb said:

    Actually, I found the link and here on Gaussmarkov! It’s the Tone Reaper –

    Dr. Robb

    Posted 02.05.2010 at 9:25 pm

  18. Justin Marshall said:

    Just built your excellent layout and it works great through my amp. However, when I route it though my condor cab sim I get an annoying crackel. I have tried different Bias settings without success, what should the Bias readings be? Any ideas?

    Posted 25.05.2010 at 3:35 am

  19. Bronsonrock said:

    I’m finding that the Bright switch doesn’t seem to do much. How much of a difference does it make in your buiilds of the pedal? I’m wondering if I got something wrong or if it’s just subtle. Thanks!

    Posted 11.07.2010 at 9:42 pm

  20. kevin07 said:

    what is the size of the pcb??

    Posted 09.09.2010 at 12:27 am

  21. Daniel said:

    I’ve build one, but I got some problems with a whistling noise when turning on the bright switch, and I think the output seams very low, way lover than bypassed? Any help?
    Thanks in advance.

    Posted 14.04.2011 at 3:14 pm

  22. Matt said:

    I was wondering, since I see no trim pots on the photo image above, how to set them. They look like they’re set up to control the drain off of the transistors. If that’s the case, are we looking around 4.5? Thanks, Matt

    Posted 13.12.2011 at 8:33 pm

  23. Psean said:

    Great layout. Thanks. Nice and compact and works perfectly. The Thor has to be the best distortion I’ve played so far. It has a LOT of output and I have to run the volume pretty low. Strange that some of you have had low output.

    As to the bright switch, it’s pretty interactive with the gain pot and a lot more noticeable at lower gain settings.

    Posted 16.11.2013 at 12:48 am