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, May 14, 2015

Electro Harmonics Pulsar Tremolo

Here's the original EHX Pulsar trem from the 70s (not to be confused with the modern Stereo Pulsar EHX manufactures today). It features Intensity and Speed controls as well as a switch to go between a hard and soft wavefrom. Original units often suffer from clock bleed from the LFO section. So I've drawn a second layout with mods to try and fix it. The 470Ω resistor above the IC and the 47µ cap below Q1 should be tweaked to find the values that work the best. Pots can be board mounted from the solder-side using right angle PCB pots.





23 comments:

  1. i like the sound it produces in this diy pedal but there's a heartbeat when you're not playing it.. i tweaked it last night and nothing happen. is there any way of eliminating that noise?

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    1. Which version did you use? The stock one or the modded one? The modded one is supposed to get rid of that clock bleed.

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    2. i used your version but it didnt get rid the bleeding.. =(

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  2. Hi man, What you think that sound better, this tremolo or the EA tremolo? Thanks

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    1. I'd probably got with the EA as this one can have some ticking issues. Consider the Heart Throb trem too. One of my favorites.

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  3. No pude solucionar el latido...

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    1. Utilice el circuito sin mod y salio andando!!!

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    2. This comment has been removed by the author.

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  4. Today i built the mod one, in my case there is a interesting issue, i had to invert the TL071 to got the effect. TL072 works at the first time when following the scheme and sounds better!
    Here the mods that i did: Cap 470 ohm changed by > 560 ohm, Q2 and Q3 > 2N3904
    Thanks a lot!

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  5. I was wondering is it possible to get more intensity (depth)?

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  6. it is possible to add a tempo led? thanks!

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    1. Here's your solution
      https://www.diystompboxes.com/smfforum/index.php?topic=38178.0

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  7. I have built the modded version. I used a 2K trimpot in the place of the extra resistance. Does not seem to help any ways. There is bleedthrough ticking in one of the mods, the more intense one. The other on is dead silent any ways. I tried to swap the IC. Here are my results:
    TL071 - ticking quite loud.
    TL061 - so far the best. Sometimes dead quite but not flawless.
    UA741 - loud ticking
    NE5534 - even louder ticking
    CA3130 - extreme loud ticking and hiss
    Also, speed pot is reversed.

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  8. Hello! i have built the stock version, how can i modify it to modded version with existed PCB? Please write me to s992s@mail.ru email if you know, and sorry for my english

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  9. It works, the drawing is good. I built a few pedals from the drawings here. Thanks for them.

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  10. Hey. I don't understand. The last image, black and white, we have 4 holes at the four ends. But in others 3 images there is just 1 hole, the ground.

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    1. They're just extra ground pads if you need them. Nothing special

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  11. I made a different pcb design if somebody are interested, I build this today and works great so far. NO THICK

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    1. can u send it? tonycardenas1409@hotmail.com

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    2. Sure, I will send a pcb guide that I made to avoid thicks and pops. Includes the "Pekka solution" to fix the drastic increase in rate pot at the end. Be careful to install jacks as far as you can from rate pot and rate solder points too.

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    3. Hi!

      Could you please send your PCB design to timi4mi@gmail.com?

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  12. Hi,

    I've built the stock version. The guitar signal coming through, and there is bleed from the LFO but no tremolo effect at all. Do you guys have any idea what to check?

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