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.

Tuesday, September 5, 2017

Valve Wizard Engineer's Thumb

A little blog update: You may have noticed there wasn't a post yesterday and that there is one today. Why on a Tuesday and not a Monday? Some big-ish changes are coming to the site in the near future, which (along with a bunch of other small things) is taking up a lot of my free time. So don't freak out. I'm still here. Layouts are still coming. Just not quite as frequently (2 a week instead of 3). Now that that's out of the way...

Here's the 5-knob version of the Engineer's Thumb compressor. Been meaning to do this one for a while and decided to do it in Eagle. It's generally considered a Dyna-Comp/Ross Comp killer, and uses one side of an LM13700 chip in place of the old CA3080. This one will fit in a 125B with all 5 pots board mounted. The Bright switch is off board, but that's just 2 wires. If you don't feel like etching, you can get a board fabricated off OshPark. Original info on the circuit by the designer can be found here.



Build doc here with schematic, BOM, and drilling template.

28 comments:

  1. Thank you so much (this phrase is very weak !)

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  2. I'm interested to know how this turns out for people, I did not have a very good time with this circuit (two knob)

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  3. Verified. Since I wanted to make signal paths bolder rather than ground, re-made a pcb by hand drawing based on the above PCB layout. Works very well. Thank you for great layouts!

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  4. Could we get a layout that uses a ca3080?. If i were to build this, could I ommit pots that I don't plan on using?

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  5. Stunning!!! Threshold, Ratio, Attack, Release, & Level !!!
    What more could you ask for?
    Look anywhere & everywhere and you won't find anything nearly as precision as this. This is truly remarkable.
    To have a compressor with these features and obvious potential quality available to the DIY community is simply phenomenal! I personally have been searching for several years for a compressor that I could build that has this kind of precision and quality. Now I've found it. Thank you so much!!

    To Jose & Kevin:
    There are lot's of simpler DIY Compressor circuits available here & elsewhere. Just click on the Compressor link under the "Type" heading above & to the left. You will find several very fine compressors that are not nearly as complicated.

    As for me I can't wait for my boards to get here from OSH Park!

    Thank you again! You guys Rawk! And for free ?!?!

    Will Kenworthy

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  6. Yesterday I built it, in guiatrra it works very well, today I try it with bass. I could prove that the release to the maximum distorts noticeably.
    Excellent project, thank you!

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    1. Hello, I also finish it and the release control when I take it to the maximum also saturates a lot, and also happens to me but a little less with the control of the threshold, could you solve it?

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  7. Yo, is it just me or is that ratio pot reversed?

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  8. Can I use lm13600 instead of using the lm13700?

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  9. Any chance of a perf board version?
    please?

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  10. Salve, complimenti per il tuo grande lavoro!
    Quali modifiche per adattarlo meglio al Basso ?
    Grazie in anticipo.

    Hi, congratulations for your great work!
    Which changes to better adapt it to the Bass?
    Thanks in advance.

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    1. From my understanding it works fine on bass as is.

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    2. to use with bass I change
      1.Relase pot from B1M to B500k and resistance of 100k in series.
      2.C3 and C4 from 1uf to 2.2uf and C5 from 4.7n to 10n.
      Hope this can help you

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  11. Hello, after having finished the scheme it seems to work correctly, but I have a problem with the release pot, when I put it to the maximum the sound is distorted or saturated. Does anyone know what the cause may be?

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    1. Try a 100k resistor added to one of the pot lugs so resistance doesn't get lower than 100k.

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  12. In the original schematic and the one on the BOM pdf both lugs of the Ratio potentiometer are not connected together and in the pcb they are and C6 and R11 are in the opposite order of the original schematic. I don't know if any of that makes a difference or not.

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    1. It's actually the newer schem from Valve Wizard that has C6 and R11 reversed. The original one for 2012 has it the way laid out here. Regardless, it shouldn't make a difference, and neither should the extra pot connection.

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  13. When I turn the threshold up nearer max it starts to distort...is there a way of fixing this?
    Thanks

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  14. Hi! Thanks for the layout!
    Got an issue with this one, though.

    Using TL072 I get an annoying sound added to my notes, like an octave up kind of deal.
    It does not replace the original signal, only adds it into the mix, if this makes any sense.
    I had a similar result in your Talons OD.

    I replaced all TL072s with 4558. Talons works fine now, but this compressor seems to have a tremolo sort of effect on note decays. Sounds as if the unit does not know if it should bring the volume up or down, and the sustain sounds like it's "struggling" with itself.

    Will this compressor work if I replace TL072 with TL082 or TL062? If so, what difference should I expect?

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  15. this! please! http://www.valvewizard.co.uk/engineersthumb3.html

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  16. This comment has been removed by the author.

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  17. I made this twice. I added a 30K or something in series with the release pot and a 4.7K to the centre log of the ratio pot and it calm her tits. Bumped those 1uf electrolytic caps to 2.2 I use it for my electric piano it goes lower than the guitar. It's not a subtle compressor, but if you can get it to work, it can pull down rather large transients for it's size.
    If you use it for your guitar, make the DOD envelope filter too, put it after this comp, and you'll go "Ahhh!"
    Thanks to the kind loving dude who puts these up, making life easier is what heroes do.

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  18. I had already built this one and it works fine. More power to the designer! Keep in rockin'

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  19. finished it and the compression changes are very subtle. time to double check. anyone having the same issue?

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  20. This compressor hits hard!!!
    I had the same issues you guys have described. The inverted pot and the distorted sound with release. I didn´t bother fixing release pot since it´s just you put it in the right position. I inverted the connection in ratio and it´s working like a charm! Thank you very much for all the layouts you put here!

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