G. Collier’s RunOffGroove Thor

by gaussmarkov

G. Collier's Thor (POV-Ray image by Eagle3D)

A basic goal of gaussmarkov.net is to provide support for designing your own build. Not only can you get PCB images, but you can also get Eagle CAD files for those images that you can rework. Because the PCB design is already verified, you can be confident that your version is going to work also.

This post is the first of a series that will offer projects by others that are based in part on gaussmarkov.net projects. George Collier took the Thor circuit from runoffgroove.com, the Eagle files from gaussmarkov.net, and put in his own 3 band active tone control. Here’s a gut shot of his build. If you view the image in another browser window, you can see it full size.

G. Collier's Thor board

George is using his Thor as a preamp in an amp he built and calls the Tone Reaper. “I also attached a shot of the cabinet the preamp is housed in. It’s been rebuilt a few times now to implement some changes since it was first built in 2007. It’s a totally different animal now! I’m using the the Thor with the tone control as a preamp, feeding an LM3875 amp. The cabinet is open back and has a single Eminence 12″ Texas Heat speaker. The LM3875 can drive this thing loud…very very loud :)”

G. Collier's Tone Reaper Amp

Here is a link for the Eagle files George zipped together: gcollier-thor-project.zip. “The layout I sent you is a tad different than the one I am using. The differences are very small, only some slight changes to the ground plane and also I put the diodes for the bridge rectifier on board rather than having to use a separate rectifier. I included pads to power it by a battery or a wall wart (in case you want to use it in a pedal enclosure), if you do this there is no need for the regulator and all the associated parts. Definitely DO NOT plug in a battery if you are using the on board supply. You could actually use the battery connection as a take off to power a pedal if you wanted. I’m sure this layout could be made even smaller (rotating all the tone control components 90 degrees would likely do it).”

For reference, here is an Eagle3D rendering of the layout George sent:

Eagle3D POV-Ray Rendering of G. Collier's Thor

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

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6 Responses to “G. Collier’s RunOffGroove Thor”

  1. gaussmarkov said:

    i made a pdf project file for this one also: gcthor-project.pdf

    Posted 09.08.2008 at 10:55 am

  2. – Redwolf – said:

    Thanks a lot for the files and information. I’ll be attempting to build it on the next weeks, modding it with on-board pots. If I’m successfull I’ll let you know, it’s the hardest project I tried.

    Thanks again,

    – Redwolf –

    Posted 03.01.2011 at 9:27 pm

  3. David McGregor said:

    Nice idea. I am in the process of building a 5 Watt, class A tube amp, and need something to drive it with. It is still a toss up between this and the doctor boogey (guitar head should have the presence control IMO).

    Posted 14.03.2011 at 3:32 am

  4. Sebas said:

    First of all, THANKS!!!

    I did Dr Boogie and it’s awesome.

    I’m trying to debug this Thoir Tone Reaper and maybe someone can help…

    Bypassing Tone switches it Screams!! but there is something strange when I engage the EQ… the 3 pots T,M,B are reversed but I re-checked wiring 3 times… The funniest thing happens when you dial T and or M down, they individually boost the gain! If you dial them up they cut the signal. Bass pot appear to be OK… I double checked the PCB against Schemathic and didn’t find anything wrong, also Eagle says that they are consistent. Any help will be appreciated. Thanks AGAIN!

    Posted 10.02.2012 at 7:13 pm

  5. Jaco said:


    the transformer with feed the circuit its a 12V?

    73 dx!

    Posted 29.01.2013 at 3:36 pm

  6. Moo said:

    @ Sebas
    I Have the same Problems:
    Screaming / T- and M-Pots boost gain, Bass Pot ok.
    Also checked PCB against schematic and didn’t find any failures.

    The design of the eq stage must be wrong.

    Posted 23.02.2013 at 12:51 pm