Dr Boogey

Build name: Red Devil

Background

This is actually my third attempt to build this pedal. The first time I tried I messed up PCB while etching. The second time I build it on perfboard with some cheapo pots. It was waiting for an enclosure for a while and I lost interest in it. Over a year later I got etched PCB from John Lyons (a fellow DIYstompboxes.com forum member) just because it looked cool in blue. Another year or so later I finally got some time to finish the pedal. Board I got is made using the improved Dr. Boogey circuit from Gaussmarkov’s PCB layout. Changes from the original design are Miller capacitors added from gate to source, tone stack scaled by 10 and maybe few minor changes.

FET emulators

Before I go into details, a few words on FET emulators in general: the idea behind a FET emulator is to take the preamp of a famous amplifier and replace each tube triode with a FET. Using FETs instead of tubes has a couple of advantages: FETs are waaaay cheaper than tubes and FETs work with only 9V while tubes use at least 250V (in this case Mesa runs preamp tubes at voltages around 400V!!!). Next, FETs are much smaller so you can pack whole preamp into medium sized stompbox and use it as distortion/ovedrive pedal. Finally, unlike tubes, FETs won’t wear out. On the other hand, some argue that FETs don’t sound as good as the real thing. Their clipping characteristics are not the same. In my opinion this amplifier is a perfect candidate for FET emulation because it’s not very smooth sounding amps. Solid state devices tend to clip harsher than tubes.

Below is a typical tube gain stage “translated” into a FET gain stage. To bias a FET plate resistor should be set to make a voltage on the drain a half of power supply voltage, in our case 4.5V. For this purpose 100K trimmer is often used instead of a fixed resistor because it lets you dial in voltage easily and play with it to find the sweet spot. On the other hand, trimmers reportedly induce noise, so I put a socket instead, used a pot to tune the voltage and then replace it with a fixed resistor. The second difference between tube stage and FET stage is a capacitor between gate and source which emulates Miller capacitance found in tubes. All other components remain the same, but now high-voltage components are not required because we work with 9V only.

Video Clips

Click on a thumbnail to play the video on YouTube.

Click here to list all 3 related video clips.

Pictorial

Click on a photo to see more details

All FETs are J201 biased as close to 1/2 of B+ as possible with resistor values I had around. There are only two changes I made to the circuit: 47uF filter caps instead of 100uF (I only had those) and 2K pot for Middle instead of 2.5K which was hard to find. I reckon that even 47uF is more filtering than needed and I’ll play this pedal mostly scooped anyways, so having a bit less middle range doesn’t matter at all.

Results

And the result: AWESOME!!! It turned out to be better than I hoped for. It’s very quiet noise-wise and sounds great. I can nail Dream Theater tones rather well, which is what I planned to do with this pedal. It has more much gain than I really need, I don’t expect to crank it above 50% at all.

Useful links

Gaussmarkov’s Dr Boogey page
Mesa/Boogie Dual Rectifier schematic
RunOfGroove.com page with few interesting FET emulators
Bucksears’ page with few FET emulators including Dr Boogey

Comments
22 Responses to “Dr Boogey”
  1. MassaM says:

    Hi Bancika,

    Nice stuff and your guitar playing is awesome. Been following your youtube videos.

    Regarding the Dr Boogey pedal, I have a question if it is possible to have a truebypass with DPDT as I am aready have a lot of them also unable to get the 3PDT part in my area.

    Please asist with a diagram if possible.

    Many thanks and keep up the awesome work.

    MassaM

    • bancika says:

      Thanks!

      Yes, you can use DPDT. One way (simple) is to get rid of LED indicator. The other (more complicated) involves building a separate circuit (called Millennium bypass) that can give you LED indicator and bypass using DPDT. Check out wiring diagrams at tonepad, you can grab the doc here http://www.tonepad.com/getFileInfo.asp?id=76

      • MassaM says:

        Hi again Bancika,

        Great info and thank you so much for the tonepad dpdt and the mellenium bypass which has the LED indicator as well.

        It’s both encouraging and great to have all the info in one place and one file.

        Long live DIYers. Cloned must they all be.

        Thank you and keep up great stuff you’re doing.
        Cheers

  2. eugene says:

    did you do any mods to this?

  3. vl9xx says:

    Hey Bancika,

    I’ve been thinking of building 12V re-/reverse-engineered 3* 12ax7 version of dr. Boogey just for the sake of tickling thought (if it sounds cool, it’s definitely a bonus). Since I’ve been looking throught your amp projects and you seem to have experience with tubes, could you try answering my questions.

    First of all, I’m thinking of going with Gaussmarkov’s schematic with reverse-engineering the triode -> FET change back to tubes again. Needless to say, I’m deleting the capacitors, but leaving the resistor and the other cap as they are. Mesa seems to have bias after the triode, where the dr. Boogey uses bias another way around. Do you think, I should go with Mesa’s resistor values, or should I go with constant components as done with dr. and bias the triode as in dr.? If I go just by substituting FETs with triodes, should there be anything other to consider besides the biasing pre-set (before final baising by ear)? Biased first to 6.3V (with 12V)?

    OFC it needs a new power circuit, but that I propably can figure out as well as the tube heaters (I was thinking 6.3V heater voltage). It wil not be battery powered, but moreover, I will be powered through 12V pedal power supply. The heat is naturally an issue, but I’m not trying to fit it in a regular stomp box, so there’s possibilities to prevent the tubes to heat excessively.

    Thanks in advance!

  4. supriyadi says:

    I’m Indonesian, I have been working on the final stage of my dr boogey, but until now could not function like what I expected, there was no sound at all, what do I do?‬ please help me

    • Rob says:

      Common pedal build problem. Just start at the beginning and debug the circuit. Make sure all connections are proper, you have no shorts, and make sure you have the FETs connected properly.

  5. soupbone says:

    Hey Bane,I was listening to your Dr. Boogey build.Sounds great!I wondering if you had the layout and parts listing for it?I’m going to try and build with perfboard.Thanks!-soupbone

  6. dov g. says:

    how do i buy this pedal or something very similar to it?

    • Bancika says:

      try visiting trading post at diystompboxes.com. If there aren’t any for sale there you could ask somebody to build it, it’s a common pedal on that forum.

  7. ohhoho says:

    This emulator is only on j201, right? What can i change to use other fets like 2sk30a or bf 245c?

    • Bancika says:

      you can use others, just mind the pinout. I tried MPF102 and it worked but with much less gain.

  8. chromesphere says:

    I just finished my Dr Boogey and i have to say the same, better then i expected. Best high-gain DIY pedal i’ve made so far, really ballsy, and natural sounding. Highly recommended.

  9. Leon Bruce says:

    This pedal is an amazing build, i purchased the one in this write-up from this builder at diystompboxes.com and i must say the quality and sound from this little thing is ridiculous. I’m all smile, ear to ear.

    Great write-up as well, those pictures, while very nice, don’t do justice to the pure craftsmanship that was put into this beauty. Bravo!

Leave A Comment

  • About

    The idea behind this site is to share my experience with Do It Yourself approach to guitars, amplifiers and pedals. Whether you want to save a couple of bucks by performing a mod or upgrade yourself instead of paying a tech, or want to build your own piece of gear from scratch, I'm sure you will find something interesting here. Also, this is the home of DIY Layout Creator, a free piece of software for drawing circuit layouts and schematics, written with DIY enthusiasts in mind.