Thursday, 3 January 2013

Runoffgroove Thor

If i recall correctly, someone requested this a while ago. I think that's enough for today :)

Runoffgroove's current take on emulating the classic Marshall 100W Super Lead. Read the complete description and history of the circuit from ROG.




21 comments:

  1. Cool, was just about to etch a PCB for this, might just give the vero a shot first. Your on a roll so far this year.

    ReplyDelete
  2. I played on one of these a while back and liked it lot, but I really liked it best with the bright switch and bottom switch both on. If I wanted to remove the switches from the circuit and just have it wired as if both are always on, should I just connect the bottom sw1 and bottom sw2 and do the same for the bright switch?

    ReplyDelete
    Replies
    1. A bit late for an answer but experiencing this one i found that bypassing the 100k resistor with the bottom switch gives less bass actually. So bright switch 1 and 2 should be linked but not bottom switch 1 and 2.

      By the way I've tried to replace the 33k resistor of the bottom section with a 10k resistor (grounded) in series with a 50k pot (lugs 1 and 2) and found there a nice mod to adjust the bass amount

      Delete
  3. Tag this one, Miro. I've spent ages trying to debug this one only to find I might have really dodgy batch of j201s ( this might explain problems I've had with the umble too - I'll look at that again tomorrow evening).

    But anyway,I went with 4 2n5458s tuned the trimmers by ear and it sounds really lovely, thanks again for another ace layout.

    (Azabache soon!?)

    ReplyDelete
    Replies
    1. Thanks for verifying! Weird thing.. I could understand a few bad ones, but whole batch... Good thing you got it working!
      +m

      Delete
  4. I am assuming the switches are SPDT on/on Correct?

    Or is it a SPDT On/off/on?

    ReplyDelete
    Replies
    1. Only 2 wires are used for each switch so it has to be a SPST simple make or break contact and so 2 position. You could use a SPDT if you want (they seem easier to source than SPST) but you'd just use the centre lug and one of the outer lugs.

      Delete
  5. Anyone had any experience with this one? Getting some gating issues with the gain pot. Distortion works when the gain pot is all the way up. Hmmm...

    ReplyDelete
  6. i built this with a tl061 and i just get a high pitched oscillation noise and no signal. Anybody know how to fix it.

    ReplyDelete
    Replies
    1. We can try to help but not with that description, it could quite literally be anything. Have a look at some of the fault finding suggestions here:

      http://tagboardeffects.blogspot.com/2012/05/fault-finding-build.html

      If none of those help post the voltages between all IC and transistor pins and ground to see if those help narrow it down.

      Delete
  7. Hey Guys,
    I have built this great circuit and it is just awesome sounding. Much better than most Marshall-in-a-box I tried and a bit fuller than the almighty Wampler Plexi-Drive.
    But, there is one thing that is driving me insane. There is a great deal of hiss on this pedal. Whenever I stack it with a fuzz, a booster or just with another overdrive it stands out as the cause for major hiss.
    Anyone has any idea how to solve this thing? it doesn't matter if the BRIGHT switch is engaged or not, As soon as the VOLUME goes up, the noise becomes audible.

    Thanks,

    http://fuzzquest.blogspot.com/2012/04/rocking-marshall-world.html

    ReplyDelete
    Replies
    1. Is everything that should be grounded grounded ? Input jack ?

      Try a buffer before and after the circuit, maybe that might help.

      Delete
    2. I'd definitely get rig of the trimpots (considering you are using them) and use shielded wire for a few spots like input and at the gain control. Trimpots are kinda evil, IMO. I have a little vero prep'd for a Thor build and I'm totally sure I won't be using trimpots for it. I'd rather use regular 16mm pots or wires connected to alligator clips until I find the right resistors.

      Delete
  8. I got this one technically working last finally (I had a few "tracing" errors) but it is finally audible. BUt it is VERY treble and hissing noise. The J201 seems to be the mot prone, any slight modification to its trim pot changes it from dentist drill to pneumatic hammer.

    Not sure what to do - this circuit is very sensitive to it components - Qs and ICs.

    ReplyDelete
  9. FYI: I finally found a cap that was terminated in the wrong strip. I changed out some ceramic for silver mica caps, and put in one multilayer cap in pace of a 220p ceramic. Anyway - suddenly it all works, and that is good. Got all the transistor dialed in and it sounds not too bad. This was one of my more frustrating builds but its always good when you get it worked out.

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

    ReplyDelete
  11. Right, mine doesn't work, in part. I can tell vol, gain and the switches work, but the hum that comes along with the gain is so mother-effing loud that makes the pedal impossible to be used. There's also this high-pitched oscillation when dialing the gain back.

    Readings in volts:

    Q1: D: 6.44/S:0.45 /G:0
    Q2: D: 4.56/S:0.33 /G:0
    Q3: D: 9.38/S:4.81 /G:2.34
    Q4: D: 4.35/S:0.38 /G:0

    IC:
    1: 0.15
    2: 4.68
    3: 4.26
    4: 0
    5: 0.15
    6: 4.68
    7: 9.39
    8: 0

    Q3 and some pins of the IC look weird, let me guess? I have checked for proper cuts, links and component placement and can't find anything wrong. I have also cleaned between the tracks to get rid of any stray bit of solder and tried different transistors and still the same monstrously loud hum. Any help is appreciated!

    ReplyDelete
    Replies
    1. Update:
      After changing a couple caps, trimpots and experimenting with even more transistors and still getting the same super loud, never-ending dentists drill hum, I was about to give up on this, until I moved some of the transistors with my fingers a few times and I managed to make the noise disappear (for a while). The circuit started to behave like a regular OD pedal, without oscillations when dialing the gain back, and just a normal amount of OD hum. I'll try getting rid of some of the sockets and see what happens. I still feel the problem is Q3 or somewhere around it... more updates later.

      Delete
    2. Right so, probably my final update here: indeed the issue happened to be a bad contact at Q3 - I managed to get it working right just by gently tapping the transistor a few times - I think the socket is "rotten" or something...

      Tone review: extremely similar sounding to the Wampler Plexi Drive (or vice-versa, I don't know which came first) but doesn't seem to have the slight mid-scoop and tighter bass the PD has. Other than that, very very close, what makes sense, since both are based on and borrow from the circuit(s) of the original amp(s). I haven't tried stacking and can't comment on noise levels since mine isn't boxed. The bass switch seems to make it even a little fatter than the PD's does, but I haven't compared them side-to-side.

      Delete