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Saturday, 20 January 2018

Jext Telez White Pedal

"A boutique pedal homage to the unique onboard overdrive circuit in vintage solid state Vox Conqueror amps that George Harrison used on the White Album and other Beatles recordings. The White Pedal has four knobs that control volume (overdrive), gain (fuzz), treble cut, and a bass cut knob that acts as a mid-boost, while a fifth knob (the Yoko knob) selects the midrange frequency to boost for a parked wah sound"

Original FSB thread and schematic available here.
Schematic should be correct but it's not verified yet. 


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100 comments:

  1. Unknown20 January 2018 at 20:25

    This actually sounds really neat.

    ReplyDelete
  2. Hozy3123 January 2018 at 17:41

    Does anyone know if i can use a Fasel cup core as the inductor as I have a spare. Can't seem to find any info on its inductance.

    ReplyDelete
  3. plonkster24 January 2018 at 07:41

    Alex, you can't believe happy you just made so many people...
    Hoping to verify this soon, just waiting for the inductor to arrive !

    ReplyDelete
  4. Marc24 January 2018 at 13:56

    I once gutted a dunlop wah to put in a Area 51. Is the inductor in the Dunlop fit?

    ReplyDelete
    Replies
    1. Alex24 January 2018 at 17:41

      I think the original uses a Whipple Wah inductor.
      Need to test others to see.
      They need to measure 500mH (more or less).

      Delete
  5. Unknown24 January 2018 at 16:21

    Thanks a lot ! Can you confirm C1 is 300n as in the schematic ? (currently ordering some parts needed).

    ReplyDelete
    Replies
    1. Alex24 January 2018 at 17:43

      The guy that reverse-engineered the pedal has measured 300nF.
      The original amp schematic states 1uF.
      Not sure which one is correct but I would go for the 300.

      Delete
    2. Unknown25 January 2018 at 11:07

      Ordered both. I will socket this in first time. Thanks again.

      Delete
  6. passaloutre24 January 2018 at 21:31

    Hey I'm the guy that traced this. Anyone who builds one, let me know if you run into any problems and I'll see if I can confirm on the original pedal (I still have it disassembled).

    ReplyDelete
    Replies
    1. Unknown25 January 2018 at 11:06

      Speaking for a lot of people, I would say : THANK YOU !

      Delete
    2. Iago26 January 2018 at 02:46

      Thanks for the effort and sharing, Michael.

      Delete
    3. Fever van Roode26 January 2018 at 20:43

      Micheal: Thanks for sharing.... can you check the Gain pot connections compared to your schematic? Just noting the difference in this Vero board and your schematic as I am looking to make up a PCB layout.

      Delete
  7. Unknown26 January 2018 at 01:16

    Thanks so much for this one!

    ReplyDelete
  8. Fever van Roode26 January 2018 at 06:01

    Are the gain pot pin connections reversed? Pin 1-2 should go to the cap/resistor and pin 3 to the BC538?

    ReplyDelete
    Replies
    1. Fever van Roode26 January 2018 at 15:15

      * BC548*. :)

      Delete
    2. Alex26 January 2018 at 15:17

      That's based on the schematic but the board connections looked reversed.
      Easy to swap anyway.

      Delete
    3. Fever van Roode28 January 2018 at 19:38

      You're correct. I looked at the schematic and it doesnt show the PIN numbers ... the usual pins are reversed (3 to right of the sweeper) on the Gain, Treble and Level Pots. Bass is normal pins.

      Delete
  9. KDMR28 January 2018 at 04:02

    awesome. been looking for the schematic for a while now and this is the next best thing.

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  10. Fever van Roode28 January 2018 at 19:36

    The trace cut at coordinate Y10 should be one row lower at Y11.

    ReplyDelete
    Replies
    1. Alex28 January 2018 at 22:32

      Thanks but I'm not sure which one is Y10 (no cut). I've found an extra cut that wasn't supposed to be there under the 220R resistor (L/25).
      Layout has been updated.

      Delete
    2. Fever van Roode29 January 2018 at 03:04

      Use letters for the columns and numbers for the rows - starting from upper left corner.

      Delete
    3. Fever van Roode29 January 2018 at 03:14

      and yes... that was it.

      Delete
  11. Hozy3129 January 2018 at 17:01

    If i use a 2 pin inductor does it go across the two left pins of the one shown in the diagram?

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  12. Hozy3129 January 2018 at 17:23

    Ok, i tried that and it works using my Fasel cup-core inductor. The only problem is the volume is way, way below unity. Could this be my choice of inuctor? Checked the usual culprits and all seems fine.

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  13. Hozy3129 January 2018 at 18:03

    I was wondering about the two 150nf and 56n capacitor. They are not in the schematic?

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    Replies
    1. Fever van Roode29 January 2018 at 18:12

      These are summed capacitance as the layout uses a SPDT mini toggle switch. The original used a rotary switch and could switch the capacitor values directly. Alex did some magic here and used capacitors connected such a way to work properly.

      Delete
    2. Hozy3129 January 2018 at 18:48

      Awesome! Thanks for the explanation. Still not sure why such low volume then. I have some large axial 250mH inductors that i would like to try, how would i connect, in series or parallel?

      Delete
    3. Fever van Roode29 January 2018 at 18:49

      series

      Delete
    4. Hozy3129 January 2018 at 18:50

      Sorry, should have looked it up, same as resistance.

      Delete
    5. Fever van Roode30 January 2018 at 07:06

      Do you have the same volume issue when the tone selection switch is in difference positions?

      Delete
  14. Anonymous30 January 2018 at 14:40

    Hi all. I wrote a note at FSB about this circuit. I modeled it in LTSpice and compared it with the original Vox Conqueror preamp. There is, I believe, an error in the schematic - the 20K/22K bias resistors on Q3 should actually be 11K and 2.2K and the collector resistor upped to 1.1K. Based on my LTSpice simulations, it should work with 10K/2.2K for the base of Q3 and 1.2K for the collector resistor. There are some other differences with the original Vox preamp, but this change should at least get you a healthy output signal. Let me know if this fixes the problem. I have an idea of how this could be implemented at 18V (and model the actual preamp better) rather than the starved 9V supply of this pedal, but I'll need to break out my breadboard for that. ;)

    ReplyDelete
    Replies
    1. passaloutre30 January 2018 at 16:19

      Hi Frank, thank you for your thoughtful reply and circuit analysis. Please see my response at FSB.

      Delete
    2. Hozy3130 January 2018 at 17:23

      Thanks for this Frank. So i changed the 22k for a 2k2, the 470R to a 1k2 and the 20k to a 11k. Unfortunately the volume level stayed the same. I reckon there must be something else amiss.

      Delete
    3. Alex30 January 2018 at 17:30

      Hey Gavin!
      From the pictures the previous values seem correct.
      Try reversing the 10uF cap in the top left corner...

      Delete
    4. Hozy3130 January 2018 at 17:55

      Just tried that again no difference. I was just audio probing and i'm losing signal around the 1k resistor, i think. I'll keep on probing and let you know more.

      Delete
    5. Anonymous30 January 2018 at 18:04

      Thanks for trying that Gavin. I still think the 2.2K is correct, and there may be something else going on. Try audio probing the collector of Q3 and lug three of the treble pot. There should be a healthy signal coming out of the transistor preamp/distortion stage before it hits the tone stack.

      Delete
    6. Hozy3130 January 2018 at 18:05

      I'm getting sound up to the right hand 2N4125 and i am getting it to the base of the 1k and the 47k, not getting any signal from the next 47k or any points on the BC548. Sorry if some of these aren't in the audio path my knowledge is still quite limited.

      Delete
    7. Hozy3130 January 2018 at 18:17

      Getting good signal from Q3 especially the collector and treble lug 3 is good as well.

      Delete
  15. Anonymous30 January 2018 at 18:49

    OK! Is the signal full and crunchy at treble lug 3? This should be the "raw" signal coming off the preamp/distortion. If that signal is good, then the trouble lies in the tone stack/MRB.

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  16. Hozy3130 January 2018 at 20:53

    Yes.

    ReplyDelete
  17. Fever van Roode30 January 2018 at 21:49

    Gavin: Double check your trace cuts (assuming you are on the Veroboard)... the original post Alex did had a cut under the 220R resistor that was not needed there. If you made that cut - reestablish the trace.

    ReplyDelete
  18. Hozy3130 January 2018 at 21:52

    Thanks Fever, i did build it prior to that discovery, fortunately i did notice and amend.

    ReplyDelete
    Replies
    1. Alex31 January 2018 at 11:41

      Hey Gavin!
      I put this on hold while Frank and Michael try to sort out the schematic.
      If you wanna try something in the mean time:
      reverse the second transistor from the right (2n4125).
      On the first transistor from the right (BC548) add one 1K5 resistor going to ground and one 2K2 going to the same row of the 20K, 47K and 1K (V+)

      Delete
    2. Hozy3131 January 2018 at 18:47

      Alex,you haven't mentioned from where next to the BC548 to place these resistors. From collector?

      Delete
    3. Hozy3131 January 2018 at 19:21

      Just seen Motters post on FSB collector it is. I'll try in a bit.

      Delete
    4. Hozy3131 January 2018 at 22:55

      Ok, that made no difference in volume. I think it made the whole thing nicer as it was a bit harsh. I'm using a boost after it and amp up high so i can actually make out whats going on.

      Delete
  19. 0friendsrecordings2 February 2018 at 20:13

    I've been checking in with this since it was initially posted, as I have a wah with fasel inductor that I want to do something more interesting with. Reading this and the thread over at FSB - looks like this one is still yet to be fully verified. One thing, while I'm trying to assemble components - the dark brown caps are all labelled with n but usually those oval brown caps are for the ceramic pF values. Can someone confirm whether the 68 / 100 / 47 / 150 dark brown caps in the schematic are nF or pF values?

    ReplyDelete
    Replies
    1. Iago3 February 2018 at 16:39

      Go with what's written. Visual representations might not be the most accurate every time.

      Delete
    2. Alex4 February 2018 at 09:37

      The values are correct(nF). The type of capacitor (as long as it's not polarized) doesn't matter. I always use the brown ones when the cap spans two rows because they are easier to read.

      Delete
  20. Iago3 February 2018 at 16:37

    Schematic updated @ FSB! Seems they've sorted out all of the problems now.

    ReplyDelete
  21. Strewel Peterson15 February 2018 at 22:08

    I'm pretty sure that the link grounding treble 2 shouldn't be there: think there should be a track cut between the 220u electrolytic -ve terminal and the 100n cap on its right on row 7, and the ground link moved to somewhere on the left hand side of this new cut. Otherwise aren't you just grounding most of the output with the treble pot acting like a volume control?

    ReplyDelete
    Replies
    1. Alex16 February 2018 at 08:46

      Well spotted. Link needs to be moved and it needs and extra cut.

      Delete
  22. Unknown15 February 2018 at 22:51

    That looks like perhaps Gavin's issue regarding the low volume. The circuit does not have Pin 2 connecting to ground.

    Gavin: Have you resolved your low volume issue yet?

    ReplyDelete
    Replies
    1. Hozy3116 February 2018 at 08:50

      No Haven't resolved yet. Will give this a go when i get home later.

      Delete
  23. Hozy3116 February 2018 at 14:42

    Good news, that did the trick! Works, but i need to roll back some changes i did during debugging.

    ReplyDelete
  24. Highsmith17 February 2018 at 08:07

    So, Mr. Horsburgh, is this verified?

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  25. Hozy3117 February 2018 at 11:12

    Yes, as long as you make those changes. Hopefully, Alex will update the layout. I changed quite a few parts during debugging which i think has changed the overall sound. I'll roll these back later today.

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  26. Anonymous18 February 2018 at 04:31

    I'm to the point of drilling my enclosure and wiring up. Other than the missing cut and re-positioning of the jumper I did not make any changes... so I hope to second that verification soon.

    ReplyDelete
  27. Hozy3118 February 2018 at 15:44

    Ok, I redid the board from scratch and it is now verified. My BC548s from Tayda have the opposite pinout to that in the layout, so be warned. And it sounds awesome.

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  28. Unknown18 February 2018 at 15:51

    Gavin: Which inductor did you use? I have the red and yellow and am interested in how yours sounds - audio links?

    ReplyDelete
  29. Hozy3118 February 2018 at 16:08

    I used the yellow Fasel. I'll try and put a sound clip up later.

    ReplyDelete
    Replies
    1. Hozy3119 February 2018 at 18:29

      This comment has been removed by the author.

      Delete
  30. Anonymous19 February 2018 at 17:53

    Finally finished mine up... worked well on the first try. Sounds good. I'm using a Dunlop inductor (green dot) that I had kicking around, but I anticipate buying a good one and building this again with better components. I only had generic transistors (2N3906, 2N2222) and I'm wondering if it would make any difference if I used spec parts.

    Gavin... what kind of enclosure did you use? I've managed to fit it into a 1590BB but I really could have used a little more depth to make it less cramped (vertically). The original Jext Telez enclosure looks huge. I still need to paint, so I won't have this packed up for a couple days. I'll look forward to hearing your sound clips with the yellow Fasel. I'll try to post some as well.

    ReplyDelete
  31. Hozy3119 February 2018 at 18:16

    Sorry, mine is unboxed. I have templates made out of thin compressed board that i got from packing material. They make great templates for wiring everything up. And i have enough to make them for a while. I just drill the holes for all top panel pots, etc. and judge were the dc and jacks go. Then i can take my time when it comes to boxing. Unfortunately, due to laziness and good old British weather means i have a hell of a lot waiting to be boxed.

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  32. Anonymous19 February 2018 at 20:21

    No worries, Gavin. I was just curious to see if anybody else was crazy enough to box this into cramped quarters. The 1590BB is actually a great size enclosure, but I could use another .2 inches of depth to make things just a little easier. I'll probably get a 1590XX. It has a bigger footprint, but adds that smidge of depth that I want. The alternative is a 1590C, which is just too tall for my tastes.

    Your compressed board wiring templates are a good plan. If I had done that with this pedal, I might have arranged a couple things differently.

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    Replies
    1. Alex19 February 2018 at 23:28

      This layout could probably be modified to fit in a 125B box.
      Around 23 x 24.

      Delete
    2. Anonymous19 February 2018 at 23:33

      Board mounted 9mm pots would really help

      Delete
    3. Unknown22 February 2018 at 05:20

      Hi All, New to the forum. Thanks for all the amazing work, I've gotten up to speed on this addictive hobby in a few months thanks to this site!

      I built this pedal first on breadboard, following the schematic on http://www.freestompboxes.org/viewtopic.php?f=7&t=28772&sid=4a4f0d264874bc888b28e8060fc24696&start=20#p268483, and then on strip board using a modified version of the layout above (my main mod was to put the Yoko switch and caps on a separate small board - since I had a 1P6T rotary, I added three extra options). It is an awesome pedal! I used all spec transistors, but I'm not sure it is necessary.

      I noticed a difference with the FSB schematic is that in the schematic Q7's E and B are linked. To accommodate that on the strip board layout, the cut directly to the left of E would then be moved left by one hole. Also, my inductor (Dunlop) has pins spaced more narrowly than in the diagram, so some people should be aware they may need an extra link and cut to accommodate that.
      I put this into a 1590BB (used Small Bear's white coated, so it looks close to the original!)

      Delete
  33. Alex22 February 2018 at 07:14

    There was an extra cut that shouldn't have been there.
    The layout had been drawn for a Whipple wah inductor.
    Do a Fasel legs need 7 rows instead of 5?

    ReplyDelete
  34. OcularDawn22 February 2018 at 08:07

    According to IVIarks Crybaby layout Fasel inductors span 6 rows.

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    Replies
    1. Alex22 February 2018 at 12:03

      Just wanted to male sure. Gavin or Wad may be able to tell us.

      Delete
    2. Hozy3122 February 2018 at 12:42

      Fasel does span 6 rows. I had to bend both legs in a tad to get it to fit across 5.

      Delete
    3. Alex22 February 2018 at 14:28

      Cool. I guees, if laid down, it should fit in a 125B size box.

      Delete
    4. Anonymous22 February 2018 at 16:39

      The Dunlop inductor I used pretty much fit the 5 rows that are in the layout. I had to bend one pin out a little bit, but nothing major.

      All painted and boxed up now. I'm getting some self-oscillation in the last 1/6th of a turn with the Gain pot. The fuzz is awesome at that point, but it oscillates if it does not have a guitar signal. I'll likely be building this again, source me a better inductor, and use some better parts.

      Delete
    5. Alex22 February 2018 at 18:01

      Have you seen Frank's inductorless version of this pedal on the FSB? (http://www.freestompboxes.org/viewtopic.php?f=7&t=28772&start=40)
      He has made a video and I've already drawn a layout.
      The inductor could still be used but Q2, QD3 and Q4 (from the schematic) are not actually needed cause they are part of the switching system. Does it sound like yours?

      Delete
    6. Anonymous22 February 2018 at 20:48

      This comment has been removed by the author.

      Delete
  35. Anonymous22 February 2018 at 21:10

    I was going to post a video so that we could compare the sound, but after trying a couple different guitars with my build, I figure I need to work out my gain problem. I'm not getting the good fuzz without oscillation.

    ReplyDelete
  36. Chewkey23 April 2018 at 06:50

    Hi all! Did anyone come up with a solution for the oscillation problem? I’m having the same drama... running after a buffer settles it down but loses a tonne of gain. I’d love to figure this one out, it sounds amazing when it’s not squealing like a banshee.

    ReplyDelete
  37. ShortScaleMike4 May 2018 at 16:22

    I'm also getting the oscillation issue if it's not running after a buffer. Mine was built with a Fasel inductor replacement for a Wah

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    Replies
    1. 0friendsrecordings19 August 2018 at 02:33

      I'm also getting the oscillation issue when not after a buffer. Tried a few different transistors but no joy. Got a feeling that the schematic still isn't quite right. Anyone managed to solve this one?

      Delete
    2. Unknown27 January 2019 at 00:57

      Did either of you ever solve the oscillation issue?

      Delete
    3. Chewkey27 January 2019 at 02:00


      No David, I mothballed this one. There is a perfboard layout http://effectslayouts.blogspot.com/2018/03/jext-telez-white-pedal.html?m=1 that I’ll try when I’ve got time, no complaints from that layout but limited amount of feedback given too.

      Delete
  38. Highsmith6 May 2018 at 03:53

    I just built this today, and it sounds pretty cool even ---without---the inductor!

    That doesn't come in the mail until Monday!

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  39. Joseph6 May 2018 at 11:22

    The layout says 'Wha' inductor, but Google's auto-correcting it to 'Wah'... so who's right?

    ReplyDelete
  40. Unknown6 November 2018 at 00:21

    I'm only getting a clean signal outta this thing, tone controls and yoko switch seem to work but no fuzz or distortion at all, whats the blue dot just to the upper left of the inductor? is something missing there? Can someone post their voltages?

    ReplyDelete
    Replies
    1. Unknown9 November 2018 at 00:41

      nevermind, had the transistors in backwards. Works now as it should but it's some real ugly fuzz.

      Delete
  41. Unknown24 January 2019 at 19:52

    This comment has been removed by the author.

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  42. Unknown25 January 2019 at 19:23

    I'm having trouble with this one. Triple checked layout. Voltages at
    q3
    C 7.80
    B7.62
    E7.78

    Same for q1 and q2. Voltage seems too high??

    ReplyDelete
  43. Unknown26 January 2019 at 00:16

    Did anybody ever discover how to fix the oscillation issue with this one? Sounds spot on when it's not oscillating

    ReplyDelete
  44. Chewkey27 January 2019 at 02:00

    No David, I mothballed this one. There is a perfboard layout http://effectslayouts.blogspot.com/2018/03/jext-telez-white-pedal.html?m=1 that I’ll try when I’ve got time, no complaints from that layout but limited amount of feedback given too.

    ReplyDelete
  45. Unknown28 January 2019 at 18:43

    This comment has been removed by the author.

    ReplyDelete
  46. Unknown31 January 2019 at 06:49

    I've built this twice now on vero and got the same oscillation on both occasions. Plugging a guitar is results in oscillation. If I plug in a function generation pumping out, say, 600Hz @ 0.3V Sine then there is no oscillation. It would be really good to get this oscillation issue resolved. Is there a grounding problem going on here?

    ReplyDelete
  47. tipco8 February 2019 at 18:55

    I also am getting nasty oscillation on this build, after about 1/3 the way up on the gain. I spent some time looking over the schematics and PCB layouts for this (http://www.freestompboxes.org/viewtopic.php?f=7&t=28772&sid=4a4f0d264874bc888b28e8060fc24696&start=20#p268483) and (http://effectslayouts.blogspot.com/2018/03/jext-telez-white-pedal.html), but wasn't really seeing any problems. I tried adding 1 1M pulldown at input like the PCB shows, but it didn't help.


    So I gave up looking over the schematic, put one of these buffers on the input (the 4th one), and now the oscillation is gone:

    https://tagboardeffects.blogspot.com/2014/08/buffers.html

    It seems to sound the same as it did without the buffer in place.

    ReplyDelete
  48. Nathan Snyder11 October 2019 at 21:09

    Anyone have any luck on this one? I see it's marked verified, but from the comments not many seemed to have success.

    ReplyDelete
  49. tipco2 November 2019 at 05:51

    I'd say it's verified as long as you put a buffer in front (see comment above yours). Can't say why it's needed, but it still works great for me!

    ReplyDelete
  50. Drayve8512 June 2020 at 00:30

    Very-effing-fied! I just had to swap 2n2222’s in place of the bc548’s in positions Q2, Q3, and Q4. Q4 was optional, it would work with or without that one swapped. With the original bc548’s I couldn’t get any real clipping, the signal was just clean With very slight clipping with gain knob turned all the way up. I’m using a 5kB pot for the gain so there’s not any gradual increase on it, it’s practically all or nothing. But, I doubt I’ll use this pedal on anything but 10 anyways. Great sounding pedal!!! Also it worked with or without a buffer in front of it. No oscillation whatsoever. Don’t know if it’s the type of trannys that are being used or what. Thank you for the layout!

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  51. Unknown7 December 2020 at 08:55

    if you remove the 220R under Q4, and do a link instead. The oscilation problem is gone. And you dont need a Buffer.

    ReplyDelete
    Replies
    1. Jorge23 February 2021 at 18:02

      Right on! That damn resistor!

      I built this circuit twice. The second one I was as patient and careful as I could but got the bloody oscillation issue again.
      I went through every forum and post about this build; found some value discrepancies here and there, tried all the alternatives, but it was the jumper instead the 220R resistor that solved the problem.

      I had the original and this circuit is spot on. Pretty much the same; maybe slightly muddier at lower gain settings when used as an overdrive. Great drive tones after some tweaking and of course a terrific fuzz.

      Delete
  52. 0friendsrecordings11 January 2022 at 18:56

    I had occasion to revisit this page and read the comments since I last posted a few years ago - this last one makes me want to have another go at this pedal, since I just could not solve the oscillation issue. Someone has done a tear-down of the original here https://www.youtube.com/watch?v=L01GWNK0Ap0, which reveals a few differences with the layout at the head of this post (e.g. the BC548s should be 547s).

    ReplyDelete