Monday 1 April 2013

Escobedo Harmonic Jerculator

Small and simple. Tim Escobedo's adaptation of Interfax Harmonic percolator. This demo vid is not necessarily 1:1 with the schematic, but it should give you an idea what to expect...



31 comments:

  1. Hi everyone,
    Can it work with a 2nd 2n3904 as Q2?

    Tanks!

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    1. No it needs to be a PNP transistor, like the 2N3906 shown in the layout.

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    2. Ok! And what about a BC560?

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    3. Yes that is PNP and so will work

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    4. Ok, gonna try that. Thanks again!

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  2. Ok you can tag this one. I added an extra couple of columns and put in some sockets so I could add clipping diodes between the end of the 100nf coupling cap and ground just to see how that sounded, without the diodes in it's exact to the layout.

    To be honest I mainly built this because of the name, anything called a Jerculator needs to be investigated, the only problem is I can't work out if I like this or not. On some settings it seems really sweet and others not so much. I think I'll try some different transistors and see if it can win me over.

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    1. Cheers!

      I'll tag it.

      Yes, the original Harmonic Percolator has diode clipping at the end :) You could also consider taking a pot between the clipping diodes and ground - kind of like the ZVex Machine. That could be nice addition..
      +m

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    2. Nice idea, I'll definitely be giving that a go.

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  3. This was the first pedal I ever built and the reason I got hooked on pedal building, it has a lot to answer for :-) as a complete noob I bought all the parts from my local maplin so it's probably one of the more expensive builds I've done.

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  4. Could I use a PNP germanium ? Seems like a fun adaptation.

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    1. Worth a try. It will work, but i don't know if it will sound better ot worse when compared to 2N3906.
      +m

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  5. Built one, if this is what percolators sound like then I'm afraid I dont get it. It sounds ok but not special or anything, think this one might be a seller.
    Thanks for the layouts as usual!
    Dave

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    1. The genuine Percolators had clipping diodes in them, I added some to this layout and it adds a little something, I agree though that it didn't exactly bowl me over. I don't think I bothered to box it.

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    2. These (this and percolator) need to be played loud and on the clean. It may not be suitable for all, but anyone looking for Albini/Shellac sound should keep an open mind...
      +m

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    3. Built this, there's quite a bit of oscillation on super high gain settings, and at lower gain, it does this sort of half-overdrive,half-fuzz thing which is cool, but something I could pull out of a bunch of other pedals. This one's just okay. Not getting boxed.

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    4. It's definitely got some 'sweet spot' settings, my main problem was that I went from really liking it's sound to hating it with just a quarter turn of the dial and in the end I did't think I'd get any use from it.

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    5. I made an accidental discovery with this pedal and thought up some mods. Whilst testing, i accidentally knocked the croc clip of that grounds the board and all of a sudden the pedal burst into glorious auto occsillation which changed dramatically with the guitar's volume control. Therefore I am going to add a footswitchable ground lift pot, similar to the one on Devi Ever's hyperion. I'm also going to use Madferrets idea (thanks man!) of using some clipping diodes but using a pot in series with them to change the degree of clipping, again I'll make this mode footswitchable. I'll give this a go later and if anyone is interested maybe I could give details to Mark or Miro to post here....
      Cheers
      Dave

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    6. Well a couple of hours experimentation/mutilation and I've managed to make something quite interesting out of this. I'm so impressed with the result I might consider making a few just to sell. It ocsillates, beeps and whistles, and sounds compressed and sputtery with the diode mode engaged. Good times!
      Thanks
      Dave

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    7. Sweet! What were the mods you did in the end?

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    8. Hi MF, I put in a footswitchable ground lift pot for oscillation on the fly and I put a toggle switch in and pot to control diode clipping. When you put diodes in yours, did you note a volume drop?
      Thanks
      Dave

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    9. Yeah there was a volume drop, some of the signal gets shunted to ground, ge diodes suffer worse from this than si ones. I'll dig out the board and try the ground lift, sounds like it'll be pretty mental.

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    10. Ah, glad i used silicon ones. Yes, I used a b5k pot for mine but anything up to 20k will be fine. One important thing to note, dont connect the volume pot to the board's ground, instead, ground it via the ground lift pot (obviously connect it to the lug that would be connected permanently to ground). Doing this means the volume still works when the pedal is in oscillation.
      Thanks
      Dave

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    11. Thanks for the heads up. Just a thought as well, using 4 diodes, 2 in series each way, would help to combat the volume drop if it's an issue. The only drawback would be that you'd get slight less clipping, maybe something to play with if you're going to make some to sell?

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    12. Yes I did try it with 2 pairs but I felt the difference was too subtle between clipping and non clipping modes, I wonder whether two pairs of germanium diodes may produce better results, what do you think?

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    13. If I remember correctly two pairs of Germanium diodes should clip at the same point as one pair of Silicon but with slightly different tone, maybe a bit more compression. Maybe try a pair of silicon on one side and germanium on the other as a kind of compromise?

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    14. Yes, hmm more experimentation is needed tonight so I can order parts before the tayda discount runs out haha. Thanks for the food for thought, I'll let you know how it goes, and if you do that ground lift mod, let me know how you like it.
      thanks
      Dave

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    15. I think I have a way of curing the volume difference problem. Rather than bringing the diode volume up, I'm going to investigate bringing the normal mode down so there isnt a major difference. I just hope the pedal will still be loud enough.
      Cheers
      Dave

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  6. Finished this one last night. I dig it. Fortunately for me, I am still new to building pedals so I am happy with pretty much anything that works when I get done!!!

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  7. This isn't a bad sounding little pedal - if I wanted to add clipping diodes off-board, directly on a switch - how would one do that?

    Thanks for all you guys do!

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  8. Albini in a box. Fun build. Will be a nice piece to have in the studio for harsh overdubs on post-punk songs.

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