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.

Monday, August 15, 2016

Wampler Plexi Drive

I'll give you heads up now. This is going to be Wampler Week. I laid out the Plexi-Drive a long while ago, but I wanted to give this "Marshall-in-a-box" circuit another go with board mounted pots and trimmers for those pesky J201 JFETs.


32 comments:

  1. Excellent sound, love it, thanks for project, the trimmers adjust to drain a 4.5v?

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  2. A "Wampler week" is a great idea. Thanks for your fantastic layouts!.

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  3. I was about to build the older version.
    guess I'll just wait for this one to be verified

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    1. Oh come on man, don't waite. Where's your sense of adventure? :D

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    2. coz my brain is about to explode right now bro
      my ghost echo and faux spring doesn't produce any reverb, only clean sounds
      still figure out why.
      when I'm done with my reverb, I surely move to this one believe me x_x

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    3. I feel you man. I've got like 2 or 3 ODs, a DBD (and probably a few I'm forgetting) that all need troubleshooting. Not to mention a pile of other stuff I haven't even tested... haha

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    4. that's exactly happening to me bro.
      it takes sooo much of my time, and money :D
      equal to what I get from doing all of this, soooo much FUN!

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  4. Tell me how to set the trimmers to 4.5v...

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    1. measure voltage between ground and mosfet's drain with your dmm
      adjust trimmers with your screwdriver to achieve 4.5v at each drain

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    2. awh alright, I'm good to go now

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  5. Has someone try this changing the trimpots to 100K instead of 50k?s

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    1. You might be able to get away with 100Ks. Just need to be able to dial in the right resistance for the drains of the J201s.

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  6. i build 2 pieces of this.... one with trimmer set to 4.5v, and other one 15K resistor .... i try to compare the sound, board with trimmer sounds clarity good but not enough gain for make it "rawk".... and board with resistor is very good drive..... thats my opinion...

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    1. Usually 1st cascade in tube preamps has to be trimmered to 1\2 оf the power voltage, other - 2/3 of the power voltage. In this case try to trim 2nd and 3rd cascades to 3 volts working point, this will make a good parity of the even and odd harmonics.

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  7. This comment has been removed by the author.

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  8. Any way to increase the mids just a little?
    I used all J201s and used a 1M-A pot for gain and LOVE the sound, just wish there was a way for some play with the midrange (up or down, doesn't matter).

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    1. Not sure which values you'd need to mess with. Potentially the caps feeding lug 3 of the drive pot and the bass switch, but not sure. This thread on DIYSB might help...

      https://www.diystompboxes.com/smfforum/index.php?topic=114693.0

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  9. Le falta ganancia tal vez sean los transistores falsos los j201 que seguro sea eso

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    1. Hi,

      Have you been able to solve that?
      I feel like I don't have enough gain as well. Nowhere near the videos/reviews I see for the original.
      I adjusted the trimpots by hearing it, so that the volume would be the highest. I also tried to ajust to 4.5v (and also 3v for the Q2 and Q3), but the gain was even lower.

      Thanks!

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  10. Can I use the MPF102 in place of the J201?

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  11. reduce the cap 470pf to 120pf

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  12. 470pf change to 120 pf gain loops.

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  13. Is there a parts list for this pedal above? Voltage of caps, more detailed list?

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  14. Hi,
    and thanks for your work on this page.
    What type is the 1µF cap because it is not exactly round and the different color? The same appears at the EarthQuakers Devices Dunes, which I want to build too.

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    Replies
    1. That's a box film cap. I usually get them from tayda.

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  15. Tip: works great with 2N5458, better use 10k trimmers to set the drain bias at 4.5V

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  16. does this circuit or something like this have a PCB for sale in the store?

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