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Sunday, 28 April 2013

Escobedo Duende JFET = JHS MiniBomb

The circuit for these two are verbatim. Escobedo just has a trimmer to bias the JFET, where JHS has 5K1 resistor. He probably uses matched j201s...

JHS info:
A good booster is often the most underrated tool a guitarist can own. When placed before your overdrives or distortions, a thicker, stronger and more saturated tone can be achieved. When placed after, you get your exact same tone except louder. This is great for lead passages and for causing a tube amp to naturally overdrive due to its huge amount of headroom. You will notice a slight touch of presence that lets your tone cut through the mix for those passes that you really want to stand out. Chords are heard with clarity and subtle harmonics shine! The Mini-Bomb JFET boost can do all this and only takes up a small 1.5"x3.5” spot on your pedal board!
Oh yea, and did we mention....this pedal works great on both electric guitar and bass guitar!!!
Here's Geiri's demo of his two boards in series in one A-box:

at

65 comments:

  1. Madferret28 April 2013 at 19:27

    Hey dude, you can tag this. I built it to test with the gain stage-less DS-1 that mark drew up. To tell you the truth it's not that loud, although I did use a 2n5457 as I couldn't find my J201s. Also if anyone wants to build this don't bother with the one without the trimpot. I built that one first and it was quieter than the bypassed signal, I had to add a trimmer with a daughterboard and after finding the sweet spot it was much better.

    ReplyDelete
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    1. mirosol28 April 2013 at 19:53

      Cool. Tagged. Thanks man!

      Well.. I do think that 2N5457 doesn't bias the same way as J201.. Socket and trial/error of a batch of transistors should yield good results. My batch of J201s usually bias nicely with 12k :)
      +m

      Delete
    2. Madferret28 April 2013 at 20:08

      Thanks for the info, I've got a few J201s around here somewhere, I really should label my component boxes and better. I'll have another look and try it with one but at the moment it's got the same sound as the demo video, just not as loud.

      Delete
  2. Unknown10 May 2013 at 17:41

    this was my first 1590A. worked great 1st time. I breadboarded it fist and used a b25k pot to determine the resistor value- I used an 8.2k (8.12K reading on my MM). sounds great, and has lots of headroom. unity is around 11 o'clock on the volume.

    I'm thinking of maybe putting in a bass cut switch, as it's a full range boost and can get slightly boomy.

    thanks for your great site!



    ReplyDelete
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    1. Unknown18 October 2015 at 11:26

      I agree it's a nice little circuit, and I also agree it can get a little boomy, so I'd like to add a bass cut option too, but I don't know how because I'm such a noob!
      Actually I think it might get interesting to put a bass cut knob, but then again I got no idea on how to do it...
      Maybe someone could give me some advice?

      Delete
  3. Unknown10 May 2013 at 17:44

    here's a pic... I ran out of LEDs, so I still have to add that.

    http://imageshack.us/photo/my-images/854/jwhpedalsduendeboost.jpg/

    ReplyDelete
  4. marcuspl15 May 2013 at 03:21

    really like this boost.. for something with so few parts, it really does a great job. Mine was very quiet and adds some overall sparkle, but was very transparent. Much better clean boost at first glance than the SHO clone, at least to my ears. Not nearly as raunchy though as the SHO.

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  5. BAD DREAM6 August 2013 at 02:12

    sorry for the noob question but how is the input wired on this circuit? would it go from the switch to lug 3, then into the two green wires? this one looks a bit different from most of the others..
    thanks

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    1. mirosol6 August 2013 at 06:12

      There's the Boost knob. Input goes from bypass switchto Boost pot's lug 2.
      +m

      Delete
    2. Unknown16 December 2013 at 22:14

      Ok, I am having the same issue. I wired the input to the Boost pot's lug 3, and the two green wires to the Boost pot's lugs 1 and 2. The pedal is not 'firing'. If the input wire off of the switch needs to go to lug 2, which lugs do the two green wires off of the board need to go?

      Any help would be awesome. Thanks ...

      Delete
    3. mirosol17 December 2013 at 06:59

      My earlier answer was wrong. The input wire definitely goes to lug 3 as stated on the layout.

      Your problem could be with the bias. If the JFET is completely misbiased, you won't get any singal through the circuit.
      +m

      Delete
    4. Unknown18 December 2013 at 22:50

      Yep. That was it. Thanks for the reply ... my fav project so far.

      Delete
  6. Zach14 August 2013 at 05:36

    I noticed there is no input cap to this circuit, because the input is direct to the JFET and the volume is controlled by a pot how does it affect the frequency control of the circuit, ie: more or less bass/treble in, and how does the volume control work differently then if it were at the end of the circuit like a tradition voltage divider. Also, is the is there a way to remove the volume pot and add an input cap? I was thinking it might make a good starting point for something I'm working on, but I want to control the bass frequencies, and use this to drive a second gain stage, so there would be volume control at the end that's a voltage divider.

    ReplyDelete
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    1. mirosol14 August 2013 at 21:31

      This might be a good read:
      http://www.geofex.com/article_folders/foolwfets/foolwfets.htm
      +m

      Delete
    2. Zach15 August 2013 at 03:09

      Thanks miro. I didn't see that on R.G. Keen's site. I'll check it out tonight.

      Delete
  7. Anonymous2 September 2013 at 01:46

    Alright gents... I'm tearing my hair out on this one. It's so simple, and yet I'm struggling with it! I've got it all wired up, the switch works, and all of that. The only odd thing is the gain knob. At zero, I get no signal. As soon as I turn it to about 9 o'clock or so, I get loud radio interference, and no guitar signal. At noon, a little more guitar, but plenty of radio. At full gain, I finally get only guitar. Obviously something's not working right... any guesses? I've double checked the board, everything seems to be in the right place, no accidental bridges, etc.

    Any help would be extremely appreciated!

    Charlie

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    Replies
    1. cdelbianco16 November 2013 at 14:35

      Probably grounding? I tested mine begore putting into the enclosure and got the same thing as you. Once arranged in a 1590B it worked perfectly.

      Delete
  8. Unknown12 October 2013 at 06:56

    I can't get either to boost signal. Both seem to cut it really well for me.

    ReplyDelete
  9. Neil mcNasty31 October 2013 at 15:08

    I'm having the same issue as cmengel with radio interference.
    Anyone know what might be the cause of this?
    I've checked and rechecked several times and can not find anything wrong.
    I went for the fixed resistor version, could the lack of matched J201 be the source of the problem?
    I will try to build one with a trimmer and see if I get the same issue...

    ReplyDelete
  10. Neil mcNasty1 November 2013 at 11:27

    Sorry. I'm confusing this with some other circuit. There is obviously not more than one jfet in this one, so ignor my question about matched j201's...

    ReplyDelete
  11. cdelbianco13 November 2013 at 21:16

    Could I turn this into a bass boost just by switching the capacitor value? If anyone already has tried, what kind?

    ReplyDelete
  12. Unknown25 November 2013 at 07:24

    Hi

    What should the JFET be biased at?

    Thanks

    ReplyDelete
  13. cdelbianco20 January 2014 at 01:41

    This comment has been removed by the author.

    ReplyDelete
  14. goldfixe25 January 2014 at 15:43

    Anyone know the difference b/t this and the prestige? Any layouts? I tend to lean more toward the pestige from the demos I've heard.

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    1. giudis15 December 2014 at 09:13

      hi man, have you got some news about the prestige? :)))

      Delete
    2. chumbox 21 January 2015 at 22:43

      Very little from looking at the photos of the PCB bottom. It even has a tick box for Bomb Boost and Prestige on the same PCB.

      http://proguitarshop.com/media/catalog/product/cache/1/thumbnail/9df78eab33525d08d6e5fb8d27136e95/j/h/jhs-pedals-prestige-guts-c.jpg

      http://static.weloveshopping.com/shop/music-boulevard/extra/11558591.jpg

      The transistor seems to be moved to the other side on each giving the impression maybe the pot works differently. It is on the input of the bomb boost, it may control the JFET gain on the prestige, not sure but very interested to know now. It may also use a different JFET which would explain the character difference. I agree the prestige sounds nicer and a little grittier.

      You know anything more IVIark or mirosol? I haven't seen anything on FSB since the Bomb Boost thread.

      Delete
    3. chumbox 21 January 2015 at 22:45

      Actually apologies that seems to be the pot that moves sides, so my theory is still possible. I think the transistors may be SMD cos I can't see where they connect in the pics?

      Delete
    4. Mike Lambresi18 April 2022 at 11:26

      Exactly - the pot moves sides, the 3 points in the middle are for the jack.
      https://d1aeri3ty3izns.cloudfront.net/media/14/145403/1200/preview.jpg
      https://andertons-productimages.imgix.net/46262-JHS-Pedals-Prestige-guts-C.jpg

      I wouldn't be surprised if the only change he made (for copyright purposes duende) replacing the 1M input pot with a 1M resistor and replace the 100K ouput resistor with a 100k vol pot. Alternatively he could have put a pot on the source of the tran but I doubt it as it affect the bias and this J201s dont have a lot of gain.

      Delete
  15. Unknown5 February 2014 at 13:32

    This comment has been removed by the author.

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  16. Unknown5 February 2014 at 20:45

    Hi, just finished building this and I'm getting some noise that I don't think should be there when the boost is enabled.

    Anywhere between no signal and just below max I get some interference or noise. Weird thing is after the pot is maxed out, giving me the most boost I can get, the noise vanishes but I still get a nice volume boost.

    Any ideas? Any help would be greatly appreciated.

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    Replies
    1. Unknown6 February 2014 at 09:29

      I have adjusted the bias giving me less noise with the effect engaged... but less boost too. Any way I could get more boost and less noise? Ha!

      Delete
    2. Dave6 February 2014 at 12:23

      Try a 100uf dc filter cap, and/or a 47r resistor between the 9v supply and the 9v connection on the board. Those might help to quieten any noise.
      Cheers
      Dave

      Delete
    3. Unknown7 February 2014 at 01:12

      Thanks, will give it a try and report back!

      Delete
  17. farmereffects22 March 2014 at 20:37

    I have had the same problem with really bad ground noise... I have not had radio freq but just this super loud annoying noise when the pot is between 0% and 100%. It is super weird... I tried different filter caps but that did nothing but cut the volume out of the pedal.

    What could the problem be?

    ReplyDelete
  18. Unknown24 October 2014 at 17:18

    this is an effect of a single transistor... this effect does reverse the phase, don't you?

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    1. mirosol24 October 2014 at 18:15

      How did you come to this conclusion?
      +m

      Delete
    2. Unknown25 October 2014 at 04:54

      a while ago I read an article about two boosters of a single transistor (one MOSFET and one pnp);
      I read that the boosters of a single transistor tend to reverse the phase of the signal of the guitar 180 degrees and when to use systems amp stereo the phase is canceled and the sound is very dull or opaque, so I wonder if it happens the same with this booster ...

      Delete
  19. kirshman15 November 2014 at 22:00

    Just wondering if you could add a master volume pot to this with the same instructions on the SHO compact?

    ReplyDelete
  20. Unknown31 December 2014 at 06:29

    Any solution to that noise problem between min and max of the pot??

    ReplyDelete
    Replies
    1. Unknown31 December 2014 at 06:41

      I tried the 100uf cap... lowered the volume a lot. so no luck. also tried 47uf, noise came back

      Delete
    2. Iago25 August 2015 at 03:47

      Did you box the pedal and it is still super noisy? I noticed mine was noisy but then, I didn't box it (I have to check it out later, I played around with mine very little). Often, boxing a pedal kills quite a bit of noise.

      Delete
    3. berna5 November 2020 at 08:00

      prueba con cables de buena calidad sobre todo los que van en el iinput, asi mismo la fuente , yo tube problemas de ruido , lo solucione cambiando la fuente

      Delete
  21. Unknown11 March 2015 at 03:55

    Any tips on how to set the trimmer please?

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    Replies
    1. Unknown25 July 2015 at 13:01

      Try measuring voltage between the drain pin on the fet and ground, adjust the trimmer until it's about 4.5v

      Delete
  22. John Sherrill20 September 2015 at 18:14

    Is there any way to make one of these circuits work with a MPF102?

    I've read that they are technically JFETs, but are meant for other applications. I subbed one in, but it was super quiet. Can I change a resistor or something to make up for the gain loss?

    ReplyDelete
  23. Benagro16 October 2015 at 13:59

    Hello,
    I was going to build this, but I'm planning to put it inside a plastic box because it's part of a project I'm working on, so I'm afraid it would be noisy.
    I read that the noise problem is mostly with the gain control in the middle positions, so I was wandering if it could be any help to remove the gain control (or switch it with a fix resistor) and put a volume control on the output signal.
    Any advice?

    ReplyDelete
  24. Unknown19 October 2015 at 10:54

    Hi there,
    I would like to do away with the boost pot all together, so it would be on full volume all the time, how would I wire it without the pot?
    Any help would be appreciated!

    ReplyDelete
    Replies
    1. Unknown6 November 2015 at 22:51

      Try to solder the wire "Boost 2" directly to output.

      Delete
    2. moos14 November 2015 at 18:35

      Uh, I mean, input to "Boost 2".
      Adam

      Delete
  25. Unknown30 October 2015 at 19:09

    Hey guys.
    So after building the pedal exactly like instructions are, i have a problem where if the knob is at 0, there is no sound through the pedal. But the sound does come through as I turn the knob, as well as the amount of boost. Any easy way to fix it where the pedal is on and at 8, there is no boost added until i turn the knob up?

    ReplyDelete
    Replies
    1. Unknown25 October 2016 at 02:41

      Do you still need help on this?

      Delete
    2. pouletroti26 April 2017 at 01:15

      I do!

      Delete
    3. Unknown13 August 2017 at 16:47

      I have the same problem. At 0 no sound... I built the pedal with a 2n5457. Any help??? Thanks to all!

      Delete
    4. Unknown13 August 2017 at 17:15

      Ok, I noticed that the pot is a volume and it is not a gain... than I think that at 0 there must be like my pedal does... no sound.

      Delete
    5. mirosol13 August 2017 at 17:20

      Yes. That is a feature. The gate of the FET is shunt to ground completely when the pot is fully ccw. If this is not the behaviour you want, solder something like 10k resistor in series with boost 1 wire. If 10K is not enough, then go higher with the value.
      +m

      Delete
    6. Unknown13 August 2017 at 18:29

      Thanks a lot for your help!!! Fantastic forum!!!

      Delete
  26. Unknown6 November 2015 at 23:15

    Built it with BF245A, cool little circuit. It adds a tiny bit of noise to the signal, but makes my darker sounding amp richer and brings some presence to the tone; it's always on for me.

    ReplyDelete
  27. JSA Effects14 May 2016 at 20:24

    Built this with a 2N5457 and it sounds amazing! Much fuller and more boost than my LPB1. Used a 10k trim pot in place of the 5.1k resistor to bias is. End measurement was 3.5k so swapped in a 3.3k resistor instead of the trimmer. Also tried adding some back-to-back clipping diodes to ground after the output cap (I extended the layout to be 10x5) and got some really nice overdrive tones. Well worth a play

    ReplyDelete
  28. neal gardner17 July 2016 at 09:15

    Just built and sounds fantastic. I've replaced my LPB-1 boost with this. The MiniBomb makes my Strat (96,US Standard, stock single coils) warmer, louder, and with a nice top sparkle.

    ReplyDelete
  29. Unknown18 August 2017 at 15:32

    This comment has been removed by the author.

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  30. Unknown6 January 2018 at 18:34

    I'm afraid this can pretty well run at 18 volts am i wrong??

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  31. Unknown6 January 2018 at 18:34

    This comment has been removed by the author.

    ReplyDelete
  32. Unknown6 January 2018 at 18:34

    This comment has been removed by the author.

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  33. Clay22 April 2018 at 01:37

    Is there any real advantage to firing up these single jfet boosts with more than 9v? I just bought a broken pedal. someone used the vero layouts from here for a maxon od 820 and this mini bomb in one box. I got em both working- but i was thinking I could just tap the increased voltage after the charge pump and run it to this mini bomb instead of just giving it 9v from the jack. is that doable- or worth the 5 minutes?

    thanks!

    ReplyDelete
  34. JoeyBloggs28 October 2018 at 19:48

    Looking at gut shots of the prestige and mini bomb, they use the same pcb. Anyone know the difference?

    ReplyDelete