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Tuesday, December 16, 2014

Wampler Plexi-Drive

Here's Wampler's Plexi-Drive, another Marshall-in-a-box pedal. The original unit uses a 470µ capacitor for power filtering, which seems like overkill to me. I've replaced that with a 100µ cap that should do the job just fine.

Some build reports on FSB say that the 15k resistors from 9V to the drains of the J201s might need to be tweaked to bias the JFETs correctly (4.5v), so either socket those positions or use trimpots. Also, if the tone control is too dark sounding for your taste, replace that A25k pot with an A500k to brighten things up.




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18 comments:

  1. AnonymousMarch 15, 2015 at 5:04 AM

    i fitted mine with trimpots for the drains of those j201's, i had breadboarded something like it just before and figured it was very sensitive to bias in order to get good tone out of it, but when you come around the good numbers its awesome. ill try the tone pot swap and might thinker with the bass switch...we can never have enough options can we ? :-p

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  2. UnknownDecember 7, 2015 at 6:34 AM

    Hi, I have a 3 pin on/off switch. Is it possible to use it instead of the spst by connecting the middle as SW2 and an outer leg as SW1? Thanks for the great posts. Having fun with some of your layouts.

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  3. HadrienFebruary 2, 2016 at 5:34 PM

    Hi :)

    First, thanks for your blog, it's amazing !!! :D

    The stock tone control is very useless, i recommend to put a 47nf for the tonality condensator (10nf). It works very very well ;)

    ReplyDelete
  4. AnonymousMay 18, 2016 at 8:03 PM

    I make a tweak i remove the bass switch, and I put 1M Log potentiometer to control the amount of bass, like the original two channels from Plexi, Normal and Bright.

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  5. ArielMay 11, 2018 at 3:42 PM

    hello, I just finished but it has very low volume. Any suggestions?

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    Replies
    1. Effects LayoutsMay 11, 2018 at 3:52 PM

      You might need to adjust the resistors that are feeding voltage to the drains of the JFETs.

      Delete
    2. ArielMay 11, 2018 at 9:22 PM

      Ready, thank you very much!!!! This pedal is great !!!!

      Delete
  6. blacksunzeJuly 24, 2018 at 4:57 PM

    My two years old plexidrive stop saturate,now pedal sounds like a crunch box,the original distortion disappeared ,bias at 4,5 but no distortion,help!

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  7. ANGUSJanuary 2, 2019 at 12:10 AM

    hello ,
    What is the size of the printed plate?

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  8. EETFUKApril 13, 2019 at 12:50 PM

    What is j201's replacement? In our country i can't get it because it was discontinued.

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  9. Paulo ShureJuly 27, 2019 at 8:15 PM

    work for me: https://www.youtube.com/watch?v=0y6JulnZQM8

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  10. Charvel502January 8, 2020 at 8:56 PM

    This comment has been removed by the author.

    ReplyDelete
  11. iYungJuly 11, 2020 at 12:51 AM

    Built it, love it, better than my clone TS808.

    ReplyDelete