Monday, 5 July 2010


Demo of Geiri's build:


  1. Verified.

    TL071 sounds good. I must say that i like this much more than 250, which i find highly overrated and boring.

    Like other this type of designs, you might want to consider using rev. log pot for drive - as first 30% of the pot is useless. Volume works perfectly.

    Thanks Mark!

    1. Haha I just finished this! mine doesn't work however :o(

      Didn't have any TL071's so I used a TL0712..

      Voltages are;


      I get silence when activated, bypass is fine.

    2. TL072 I meant.

    3. The pinouts are different for dual opamps mate. You'll need the TL071 or maybe something like an LM741, LF351 etc etc

    4. Ahh good. at least I haven't balls'd it (yet). I'll get some TL071's then.. and I'll be sweeping like Yingwie! or maybe not.

      He actually uses this as a dirty boost if I recall correctly.

    5. Ok noticed I have LM741's, it's alive! I get the entire gain sweep right at the end of the rotation though? Would that have anything to do with the different IC or would a reverse log be more suited as Mirosol suggested?

    6. The IC wouldn't affect that, so yes give the reverse log a try if you have one

    7. C500k pot fixed it ;o).. gradual gain sweep from start to finish. This isn't bad on it's own but in front of my dirt channel it screams! Far better than my ts9 and ZW44.. It keeps a lot of bottom end and squeels with ease.

    8. LM741 is 'really' crappy single opamp. I read about it and some of the equivalent opamps, and all of the internet seems to think that they are just bad. (Yes. I have like 20 of those left at the moment :))

      They do produce that classic sound for 250 and dist+, but i'm not a big fan of either - that's with LM741s in them. Didn't try LM301 in this yet, but what comes to 250, it lights it up like christmas tree. True. 250 doesn't sound "right" with LM301, it sounds a lot better. I guess i should try this with both LM741 and LM301 before judging it any further. TL071 works and sounds good, even if those other models fail. I might swap that B500K for C500K too..

      Vince, here's nice and short article about the difference between single and dual opamps in TL07* family:

      Anyway, even with not perfect gain control, this is very good dirty OD.

      Another thing Vince, try this with minimal gain, just before it starts distorting hard and turn volume to full. Sweet, warm roughness..

    9. Thanks, I'll have a read. I don't really like the pedal on it's own and the same regarding the Dist+. But both of these pedals were used as dirty boosts by Malmsteen (DOD) and Rhoads (Dist+). In my opinion they sound MUCH better like that. I'll be keeping the DOD as it is as it sounds sweet as a dirty boost ;o)

      i'll try the TL071 when they arrive just to compare.

  2. By the way.. Boxed this today. It's really nice OD, even for those like me - the people who don't find Malmsten that great. Sad thing that they seem to brand good designs with boring artists :)

    It's pretty close to the 250 sound, but at least in my opinion, much better.

    I'll snap photos once i get to it...

    1. I agree, I don't like Malmsteen that much.. He's amazing for about 2mins then......Zzzzzzzzzzzzzzz. But I do forgive him as he's a metal child of the 80's where lead wanking was essential ;o)

      but I do like how he gets his strat so saturated but tight/clean, and this pedal on the dirty channel with my strat, nails it.

  3. Hey Mark or anyone else for that matter, Id really appreciate some advice on this one.

    Im really frustrated with this build as I thought it would be a quick and easy build, especially as Ive build some of the more complicated veros on this blog successfully.

    Anyway, Im not getting any output from the pedal. I used all the parts as per the diagram. I used an audio probe and I can hear a distorted signal on one end of the 10k resistor (and nothing on the other end of that resistor (No signal on the side that leads to the level pot). Ive checked the resistor and it measured 10k.
    I tried replacing that 10k with a jumper and Im getting signal but its a lot quieter than the bypass signal.

    Heres some voltages from the TL071


    No idea what any of these numbers mean...
    Thanks for any words of wisdom. Ive built lots of pedals but have not much experience debugging and troubleshooting so I guess its all good experience!

  4. Your voltages look close to correct. My guess is that the signal is dumping to ground or another path. Check to make sure there are no cross connections after the 10k resistor. Maybe a stray piece of copper at the cut?

  5. Help! I just built this circuit yesterday. I have a beautiful clean tone and it's super quiet, but I don't get any drive - the pot doesn't do anything. I tested the pot with a multimeter and it works fine. I swapped the TL701 for another identical part and still no drive. Volume works fine. I tested different possibilities with the pots and still nothing. What could be causing this?

  6. Buongiorno ho montato la scheda perfettamente ma il volume e basso ed il gain non fa nulla . L'unico componente che ho diverso e il c 25p inveceho messo un 22p perche' il negozio non ne aveva ma penso che non cambi molto .
    qualcuno sa dirmi perche' non funziona. Icavi come vanno collegati hai jack in out?

  7. Hello, I mounted the card perfectly but the volume and low and the gain does nothing. The only component that I have different c 25p and a 22p why put inveceho 'the store had none but I think it does not change much.
    someone tell me why 'does not work. EVENUES how are you connected jack out?

  8. Just built this. TL061 and 22p are the only substitutions and it's not getting unity gain with the clean sound. It's not far off, but at max volume it's still noticeably quieter.

    I also get the gain bunched up at the far end of the pot turn and a 1meg reverse log pot. Any ideas?

  9. This comment has been removed by the author.

  10. Hi, this works well.
    Had a few issues and found out the diode faulty. In that case, volume was very low.
    If you are having very low volume check the diodes and the capacitor parallel with diodes.
    Now I have got a problem that is when the gain pot reaches the highest has a 2kHZ noise. tried to remove this noise by replacing 10K resister to 80K of LPF but it didn't go away. all you guys has this noise?

    1. just found the reason, I cut off the tone low pass filer in guitar that's why.

  11. Hi, tried a million tl071's, changing the cap parallel to the diodes (as well as the diodes themselves), but still can't really get it to function properly.