This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Thursday, September 3, 2015

Emerson Customs EM-Drive

Here's a really simple "transparent overdrive" circuit that was a must have a couple years ago. People compared it to the Klon and Timmy drives. Originals use paper in oil caps, which some claim sound better than modern film or ceramic caps. That's a debate for another time though. I've drawn it up so you can use big mojo caps, or with more common caps for a much smaller footprint. Both versions have a couple tweaks. In the mojo layout, I've added a pull down resistor after the gain pot to try and eliminate footswitch pop. In the smaller layout, I've added some optional clipping diodes (which I think really improve the sound of this thing), and power filtering and polarity protection.



40 comments:

  1. Hi.
    I´m looking for this pedal in Transfer Image Library and i can´t find it.
    Could you help me??
    Thanks

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  2. Looks like I forgot to upload it. It's there now in the Misc folder.

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  3. Is there a way to access this layout Via DIYLC?

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    Replies
    1. No but it shouldn't be too terribly hard to duplicate yourself...

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  4. Hey there,
    Do you have to use a battery snap wiring layout with your modified version of this pedal?

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    1. You never HAVE to use a battery snap. Plenty of builders just use a DC jack, myself included. So no, you don't have to use a battery snap.

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  5. Just verified this! Pretty decent sounding overdrive with the MPSA18. The only thing I had to do to get it sounding right was to take the 2M resistor off the 9v rail and attach it to the collector. Not sure why it doesn't work according to the layout, but once I made that fix, it sounded great. Any reason why I had to do that? Thanks for the help!

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    1. Moving the 2M to the collector essentially makes this an Electra. Plenty of people feel that improves the sound of this thing, so you're not alone (and in good company). I'm in the camp that this pedal was/is mostly hype and that there are better sounding circuits out there, the Electra being one of them (my favorite Electra clone is the EQD Speaker Cranker, closely seconded by the Lovepedal Woodrow FWIW). Did the circuit not work at all with the 2M connected to the voltage rail?

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    2. hi i'm curious, did you build it using "the mojo" pio caps? i mean those caps aren't cheap right, is it worth it?
      thanks

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    3. I've built it with Russian paper in oil caps and also with cheapo ceramic caps and to be honest, the ceramic caps sounded better. I think this was because the ceramics were more around 70-80n than 100n, so it wasn't quite as bassy. That was my only complaint with the PIO caps. Personally I don't think there's going to be any audible difference between cheaper caps and mojo ones.

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    4. Sorry for this noob question, what does it mean the 2m move to the colector?

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    5. The 2M resistor coming off the base (middle pin) of the transistor goes to the voltage rail. Some people disconnect it from the voltage and connect it to the collector (marked as C) of the transistor (so it goes between the base and collector).

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  6. It did work with the 2M going to 9v, but it was very Farty/Fuzz sounding, almost like a weird Fuzz Factory sound. I also had to turn the volume and gain all the way up to get any signal out of it. Once I moved that 2M resistor, the pedal functioned properly, and the gain and volume responded as it should. I'm gonna try some of the other Electra suggestions you mentioned!

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    1. Ok cool. I had better luck with lower gain transistors like 2N2222s with the 2M connected to the voltage when I built one a while back on vero. I think you have to play with this one a lot to really get it to sound decent. Just my 2¢.

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    2. #Charlie Richards
      I face the same problem.
      what should I do after removing the 2M resistor?
      leave it that way or ...?

      additional information, since I could not find 2M resistor, i wired 2 1M resistor each to replace it. would it give any effect to the circuit?

      thank you

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    3. I had the same ugly fuzzy sound with all the knobs at full.
      Replacing the MPSA13 (npn darlington) for a 2n3904 it work great, but haven't too much headroom/clean volume.

      I'll try moving 2M res and going back to MPSA13.

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  7. I can use 0,1uf 1000v capacitors in this project ?

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  8. I have some information that may be important:

    1. The correct value of the volume pot is really 250k but should be linear.

    2. The transistor 2N3904 also works very well in this project.

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  9. built it using 2n2222, works nicely.

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  10. I have done the circuits and I have to say that sounds very well. I´ve use the 2n2222.

    I ve made first like in the picture and then puting off de 2M resistor from 9v and puting on to the colector this leg of the resistor (like charlie richards) and this second options is better for me. More brigh and more trebbel (for my ears)

    Thank you very much dtgehring for your work in this circuit!!!

    (sorry for my english)

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  11. Where is the in and out of this board?

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    Replies
    1. Gain pot lug 3 to input, volume pot lug 2 to output

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    2. can i use metal film caps on this?

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    3. Do you mean metal film resistor?
      It is okay

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    4. Description above also mention it is ok to use modern film caps

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    5. i done building why is it when i hook into it with no power has a noisy sound

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    6. i use b250k pot = volume and b500k =gain its that ok?

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  12. now its works fine but the only problem was when i attach ground from board to 3pdt when off no hum no noise , but when I'm engage the 3pdt on lots of noise and hum, but when i pull out the ground off to the 3pdt when off has a lot of noise and hum but when i engage no noise sounds really good,. where i suppose to put the board ground? heheh

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    Replies
    1. Check out the off board wiring diagram ini the General Layout Notes tab at the top of the page.

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  13. I am with a doubt what cheap capacitors I can use, could anyone make a list? end
    How to connect the potentiometers ?, thank you.
    https://3.bp.blogspot.com/-_N9facyZYa8/VeS0OOFjCnI/AAAAAAAAF6Q/T8lndYmkMHg/s1600/Emerson%2BCustoms%2BE-M%2BDrive.png

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  14. I'll try with 2n3904 and bc548 in darlington formation.

    How this would work if I use 18v?

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    Replies
    1. As long as your components are rated high enough, 18v should be fine. Should give you a bit more headroom.

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    2. great! I'll try.. :D
      Thanks!

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  15. Do yo like more with or without 1n4148 clipping diodes?

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    Replies
    1. With the diodes. Though that definitely changes the sound.

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  16. Hi,
    I have used BC547 in reverse order and it worked great, i have also used 2 different clipping mods. thank you for layout.

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  17. Why a 4k7 in series with the LED? I replaced it with a 390 Ohm for my LED. Is that a Mistake or didn't i understand it right? BTW BC337 works nice for me. A built it point-to-point in a 1590a.

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