22 thoughts on “Dr. Boogey

  1. Hi Harald !
    I successfully made 2 dr Boogie using your layout… But my 3rd drives me mad !! Everything works, volume, EQ… But not the gain pot. I just have a very light crunch, I don’t undersand why ??
    Any idea ?

  2. Ah ok thank you. I wanted a stompbox preamp to record with impulses and maybe plug it to a poweramp for lives. Thank you for the vero layouts by the way, very convinient for us who cant read schematics!

  3. It’s a solid state approximation of the preamp stage, so basically a distortion pedal. You’ll probably have less than desirable results running this straight into most power amps, but I guess it really depends on the power amp. May be good for a DI setup or something in that vein?

  4. Is this a preamp or is it just a distortion pedal? I mean can you plug this to a poweramp directly?

  5. Hi Harald, Thanks for a fantastic site, so far i`ve built 9 pedals from your layouts and every one has worked straight off the bat first time. Unfortunately i`ve had so much fun building and playing i forgot to leave feedback and thanks for your sterling work. This was my first build and is a fantastic pedal, unbelievably versatile and by no means only a high gain one trick pony, play with them knobs theres tons of tone to be had. Kudos to you.

  6. Hi,
    I’ve made it and it works fine.
    After the first test, there was feedback problem.
    I’ve put shield wire in input and output. I put shield wire to gain pot 2 and 3 too.
    After that the pedal had less feedback but still present.
    I’ve move J201, for example Q1 to Q5 and Q5 to Q2, …. After that the feedback problem has disappeared.
    The final step was the tuning of J201. I performed tests with 5,5V, 5V and 4,5V. With this last value, the feedback problem occurs again. Finally my final tuning is 5V on all transistors.
    The sound is good and I’m loving it.

    I hope you understand my comment, I’m french 🙂

  7. Congrats on sorting it out then 🙂 I did build the JCM800, but the circuit was never boxed and has been sitting in my drawer for a long time. I can’t really tell you how they compare other than them being in the same territory.

  8. I need to check it twice before posting here….

    Must have been a bad cut, I went over every one again with my knife and viola, it works fine now. Scary gain, I love it! I’ll keep tweaking the trims to taste, thanks for the tips! Did you build the JCM800 preamp? How does it compare to this one?

  9. I don’t believe those substitutions will have any negative effect on anything. As for the lack of gain I’m not so sure. Have you got an audio probe? When I build these emulator circuits I like to tune each gain stage by ear one at a time starting with the first one. Have you considered the difference between amplitude and clipping/distortion? If you bias a stage slightly asymmetrically you’ll get less signal amplitude/volume, but more clipping which may result in more crunch. More amplitude from one stage will probably push the following gain stage harder though.

  10. Finished my build last night, I have the opposite problem, the gain seems lower from what I have been hearing in the youtube examples of this preamp. It does have a nice crunchy gain and sounds pretty sweet (all the knobs work perfect), but I expected uber gain out of this thing. I biased the j201’s drains to 4.5v, then tweaked by ear as I could get a little more gain lowering trimpot 1 to about 3v.

    Should I try some different J201s? Or do you think it’s a mistake when I built it?

    I also subbed a 22pf (instead of 20pf) for C8, and used a 27n (instead of 30n) for C17, could C8 have affected the gain stage?

    I’ll continue troubleshooting tonight for any errors. Let me know if you can think of anything…

  11. thanks for the awesome support, Harald!

    so i guess the answer is that this circuit is very sensitive to the way parts layout :-/

    i’m currently using a non-isolated input jack with the ground connected to the enclosure. do you think an isolated jack with the ground connected directly to the board would make a difference?

  12. Good to hear you’ve sorted out most of the problem. More careful attention to ground on the layout wouldn’t hurt, but that being said I’ve built this layout myself and was able to get it working without any oscillation. It is definitely a tricky problem though.

  13. ok, i rewired all offboard connections and managed to fix the issue with the gain knob. i also used shielded cables for all input and output connections.

    i still have squealing/feedback with the gain knob past 9 o’clock. putting a bypassed boss pedal in front or using active pickups fixed this. therefore, it seems like having a buffer before the circuit’s input fixes this. i will build a small opamp or jfet buffer into the encosure since i still have plenty of room in there 🙂

    do you think that perhaps using a ground strip on the veroboard next to the 9v strip may tame down feedback squealing? this pedal has crazy amounts of gain after all…

  14. thanks for the quick reply, Harald!

    i will re-check the wiring and components and see if i can find the mistake

  15. Hi, Christian. My first thought is a short or a wrong/misplaced component somewhere that prevents proper attenuation between the gain stages sending the thing out of control. I’d start by double checking that all trace cuts properly break the connection they’re meant to, there are no unintentional bridges between adjacent vero strips, and that you’ve placed all components where they’re supposed to go and haven’t forgotten any either. I also recommend visiting the debugging pages over at http://www.geofex.com (upper left corner).

    I have no experience with active pickups, but given that most stomp boxes run on 9v, which I guess gives them something like 7v of headroom, any signal larger than this is going to get clipped. Since your tube screamer works I would assume the pickup signal is fine, though.

  16. Hi,

    first off, thanks for this great site! i just discovered it a few days ago and already can’t wait to build some more vero layout pedals 🙂
    anyway, i just finished your Dr. Boogey layout today and am having some issues. i’ve checked the parts, values, soldering joints and can’t find the mistake. i also used a shielded cable for the input and have tried biasing between 5V to 5.5V

    here’s what i’m experiencing:

    1. gain is completely over the top. at around 8′ o clock it already starts getting ridiculously high and unusable. as you can imagine, it’s really hard to dial the gain knob this way (7 o’clock: off 8 o’clock ultra high gain).
    2. this also leads to massive squealing as one could imagine. at a mid gain setting it doesn’t squeal and isn’t noisy.
    3. if i run a tubescreamer in front or a guitar with active pickups it doesn’t squeal at all. not even at high gain settings.
    4. my guitar with active pickups seems to somehow ‘overload’ the pedal for lack of a better description. when hitting the strings hard the signal somehow gets unpleasantly distorted and muddy.

    i’m currently thinking about putting a buffer circuit before the input, since this seems to explan points 3 and 4.
    still, i think i’ve done a mistake in the wiring that may be leading to my ‘gain’ knob issue. i used a 1MegOhm Audio taper knob for the gain as stated on the layout.

    any help would be greatly appreciated!

    keep up the good work!

  17. Yes, you may have to use shielded cable for the input and output wires, and try to keep the pot wires short as well. And those substitutions should be just fine.
    The layouts are meant to accommodate horizontal 5mm x 5mm trim pots, but you can usually also use 5mm x 2.5mm vertical trim pots.

  18. Hi Harald!
    Do you have some suggestions for this beast? 🙂 I know it may have self-oscillation problems and maybe it needs a shielded cable for ground noise… another little thing: didn’t found on musikding the 2M resistor and the 30nf and 20pf capacitor, I choose a 2,2M and a 33nf and a 22pf… is this solution ok? another little question: when you use trimpots on vero, how much they’re big? 10mm trimpots? 5mm? 15mm? 🙂 thanks! 😀

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