Friday, 6 September 2013

Plexi-Drive with Trimmers

Yup. Most of you who know me know that i've had more than enough trouble with JFET biasing on some fixed drain resistor designs... This one also has the input cap and pulldown resistor at the input. Already verified by me. I found the best gain to be with drains at ~5V, but now you can tweak them to the voltage you want. Used 20K pot for tone. 50K should be fine too.


Posted by at 21:37
Tags: , , , ,

118 comments:

  1. milkyBK3706 September 2013 at 21:56

    Anyone know a good source for J201's?

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    Replies
    1. Unknown6 September 2013 at 22:46

      Tayda has them for $0.38 a piece. So 5 would be $1.90 plus shipping.

      Delete
    2. mirosol7 September 2013 at 09:16

      Tayda has $5 minimum on orders..

      You should check eBay too. Sadly the good deals are gone. You could score 100 piece bag in march for ~$15 but not anymore.
      +m

      Delete
    3. Unknown8 September 2013 at 19:42

      The ones Tayda sells are chinese fakes! Try Smallbear. They should still have some real ones.

      Delete
    4. mirosol8 September 2013 at 20:25

      This peaked my interest.. How can you tell that they are fakes?
      +m

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    5. Ross8 September 2013 at 21:25

      I don't think they're fake, but I believe the batch Tayda has are really out of spec, as they've never biased correctly in any build I've ever used them with.

      Delete
    6. Equinox22 September 2013 at 16:03

      Nah. I got a couple hundred from Mouser of the Fairchilds, but there are obsolete now and I'm not selling my stash. Sorry.

      http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/J201/?qs=sGAEpiMZZMvAvBNgSS9LqkIvdxYjVaKX

      Delete
  2. glabrescens6 September 2013 at 23:41

    Made 2 plexis before, no joy, 40 j201s, no joy. Now you've answered my prayers! Cheers mate, can't wait to give this another go.

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  3. glabrescens6 September 2013 at 23:42

    Made 2 plexis before, no joy, 40 j201s, no joy. Now you've answered my prayers! Cheers mate, can't wait to give this another go.

    ReplyDelete
  4. onthetundra7 September 2013 at 01:41

    I used J113's and Im not getting a ton of gain. I can hear the Marshall-like quality to the tone but its more of a light light OD right now. Guess I need to get some 201's.

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    1. mirosol7 September 2013 at 09:03

      For some reason, my builds with J201s are not as distortionish as i remembered this would be either. Those are good though..
      +m

      Delete
  5. krzabe7 September 2013 at 07:06

    Ahh this is great! I tried Plexi-drive before and I could never get it to sound right. The plexi-drive is going to be back in the build list now for sure! Thanks alot!

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  6. Doron Barness7 September 2013 at 07:42

    Thanks Mirosol for this, unfortunately I already built this one without the trimmers but now I might just go ahead and change that.
    Why change the 1N4001 for the 1N5817? any difference in practice?

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    Replies
    1. mirosol7 September 2013 at 09:14

      The polarity protection here is in series instead of original parallel configuration. 1N5817 is used because of the way lower voltage drop when compared to 1N400*. Original parallel configuration will burn/explode the diode when wrong power supply is used. This however, won't break anything - it just won't work with wrong polarity. The con to series polarity protection is the voltage drop, but with 1N5817 the drop will stay so low that it won't affect the operation in any way.

      BTW. I think i'm going to build a 18V voltage doubler for mine before boxing..
      +m

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    2. Doron Barness7 September 2013 at 09:26

      This comment has been removed by the author.

      Delete
    3. Doron Barness7 September 2013 at 12:51

      This comment has been removed by the author.

      Delete
    4. Doron Barness7 September 2013 at 12:52

      This comment has been removed by the author.

      Delete
    5. Doron Barness7 September 2013 at 19:36

      What do you expect the 18V would give? more headroom or better crunch? I might just put in a DPDT to choose between 9V and 18V using the charge pump which worked so well for the Mu Tron III and the ROG Supreaux Duex.

      Delete
    6. mirosol7 September 2013 at 20:52

      I don't expect anything. I know it gives out more headroom and the overall sound is a bit harder/colder/harsher due to that increase in headroom. Sort of like the highs of Klon.

      Finished two with voltage doubler today.

      Why i use the pumps? Because i can.
      +m

      Delete
    7. Doron Barness9 September 2013 at 18:52

      thanx

      Delete
  7. JaviCAP7 September 2013 at 09:22

    Great! I built the original one without trimmers and was a pain in the ass to bias. With this board it has to be a pretty easy build. The only problem is how to fit it in a 1590A :P

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    1. JaviCAP7 September 2013 at 16:26

      Just finished this build.... 30 seconds to bias the jfets :) really wonderful sound without wasting hours with the J201s :)

      As I supposed with the previous build, the jfets of the batch I purchased time ago, did bias at about 4,8v with a resistance of ~5k, but this time I had not to try a hundred values of resistor.

      Finally I'll be able to offer this pedal at a reasonable price, it gets built in a couple of hours instead 20 :P

      Great layout, Miro!

      Delete
    2. Doron Barness7 September 2013 at 19:34

      So your trimmers where set at about 5k to get the right bias?
      What voltages did you end up with?

      Delete
    3. JaviCAP7 September 2013 at 21:15

      Q1 D 5,06v S 0.54v G 0v
      Q2 D 5.02v S 0.48v G 0v
      Q3 D 5.40v S 0.34v G 0v

      Delete
    4. Doron Barness9 September 2013 at 11:14

      Thanks

      Delete
    5. Doron Barness9 September 2013 at 11:16

      Thanks

      Delete
    6. JaviCAP11 September 2013 at 23:20

      1590A friendly (as it should be :P) Hope you like it:

      http://imageshack.us/a/img713/3943/f3jv.jpg

      Delete
    7. mirosol12 September 2013 at 06:41

      :)
      +m

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    8. Alltrax7412 September 2013 at 08:31

      Amazing !

      Delete
  8. sleeping_for_years7 September 2013 at 14:27

    I must have gotten extremely lucky with my Plexi-drive. I used Tayda's suspect "probably not actually J201s" and it sounded exactly like the demo videos with the first two random ones I dropped in. Never went back and checked the voltage, maybe I'll do that at some point today.

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  9. chadster8 September 2013 at 03:51

    Awesome , been planning to build some wampler amp pedals , building paisley drive and ecstasy next week and if they work out I'll be trying this one and the black 65 , a layout with trimmers for that one too would be awesome.great site:-)

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    1. Iago9 September 2013 at 00:00

      + 1 for that "Black 65" with trimmers!

      Delete
    2. Alltrax749 September 2013 at 09:32

      Biasing without trimmers is pretty easy and fast actually.
      You just have to socket the drain resistors and try different values. If bias is too high then increase the value and vice versa.
      It took me 5 minutes for the Black 65 to have the 4 drains at +5V +/- 0.2

      The plexi drive was for my to do list for a while, thanks for this great layout Miro

      Delete
    3. Alltrax7410 September 2013 at 08:07

      Finished it this morning before work, I just had 5 minutes to test it at bedroom level but really like what i heard !

      Delete
  10. Unknown12 September 2013 at 02:28

    Hey everyone, I posted in open chat with no response. Any noon guides on biasing with the trimmers? Haven't biased before.

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    1. Unknown12 September 2013 at 02:29

      Noob! Stupid autocorrect. :)

      Delete
    2. drdFX12 September 2013 at 06:53

      Measure the voltage on the drain of each transistor while you adjust the trimmers. First adjust them so that the drain voltages measure approx. 5V. From there you can use your ears to fine-tune your settings.

      Delete
    3. Unknown12 September 2013 at 16:36

      Simple enough. Now, if I'm working on a layout without trimmers, would I use a pot to find the desired resistance, measure the resistance, and then replace the pot with the proper resistor?

      Delete
    4. Geezer13 September 2013 at 01:04

      Eric....yes, that technique will work

      Delete
    5. drdFX13 September 2013 at 07:10

      Or you can use trimmers in that case too, just connect them to your build with wires. Once you have the value replace with a fixed resistor of the right value. I usually do that too. If you have pots lying around those are ok too. Trimmers are atually variable resistors too like pots, just pots are more durable and are available in different tapers while trimmers are always linear.

      Delete
  11. onthetundra20 September 2013 at 00:29

    The pedal sounds soo much better with the 201's I had J113's and they sounded terrible.

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  12. Kramer8830 September 2013 at 11:36

    This comment has been removed by the author.

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  13. Unknown5 October 2013 at 14:50

    Maybe noob question here...

    Would this design also accept 2n5457's instead of j201 since you can tweak the trimpots anyway ? And if so what drain voltage would you recommend ?

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    Replies
    1. Unknown5 October 2013 at 17:56

      nvm, has already been answered on the non trimpot version. 2n545x should work fine

      Delete
  14. drdFX9 October 2013 at 10:09

    Guys, asking here because it uses 25k pots too: do you have a good source for them? Tayda doesn't have them, only 20k pots. Thanks!

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    1. mirosol9 October 2013 at 10:43

      http://www.taydaelectronics.com/potentiometer-variable-resistors/rotary-potentiometer/linear/b25k-ohm-linear-taper-potentiometer-round-knurled-plastic-shaft-pcb-9mm.html

      I've used 50K for this layout and it works well.
      +m

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    2. gogiche9 October 2013 at 11:06

      Excellent pots, I have tried them they work grate.

      Delete
    3. drdFX9 October 2013 at 12:25

      Ok, I wasn't clear enough... Tayda indeed has the linear 25k pot in plastic housing, but only linear. I'm looking for the usual metal enclosure pots if possible. But if everything else fails I'll probably stick with these from Tayda. Thanks anyway.

      Delete
    4. mirosol9 October 2013 at 12:39

      They have metal shaft ones too. Those are Alpha, so on the surface they should feel and work exactly the same as 16mm base pots, even though those are with 9mm base. Inside europe you could check out banzai and musikding, but you won't find anything at the same price as tayda.
      +m

      Delete
    5. drdFX9 October 2013 at 16:16

      True, banzai has them for about 1.5x the price :( I'll try how the linear ones feel instead of the log ones, though in this case I'm a bit surprised to have a log one for tone, those are usually linear...

      Delete
  15. Kramer8819 October 2013 at 10:56

    Hi all!

    I built this pedal three times already, sounds great, but never seems the original pedal. I set all of drain voltages to 4,8V, that’s OK. It sounds like the original pedal but with much less gain.. If i set gain pot to 12′o clock, the sound is still clean, not crunch as we hear at the original..
    Does your pedal works so? or have you any idea how can i increase the gain?
    Thanks!

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    Replies
    1. mirosol19 October 2013 at 16:38

      Try tuning the trimmers by ear. The voltage may not tell you if it's biased for maximum gain.
      +m

      Delete
    2. drdFX19 October 2013 at 18:27

      As miro said, try to set the trimmers by ear. Also after checking the original's inside (only on pictures from the web) it seems that one electrolytic cap is missing. Most probably from the source of one of the stages Q1 or Q3 to ground. I tried both, adding a 22u-47u cap from the source of Q3 to ground gave me the best result. However it is only possible on this layout if you have some components crossed above each other. You can relatively easily add a similar cap (22u-47u) from the source of Q1 to ground, and that will also increase the gain, but not that much. If you want you can try adding both caps, but to my ears that was a bit too much. Someone from a Hungarian forum also reported that adding a 47u cap from source of Q1 to ground plus lowering all three source resistors from 1k to 680R or even to 330R gives a good result too.

      Delete
    3. mirosol20 October 2013 at 14:27

      Tweaking the source resistors may be a good idea.

      Only bypass cap shown on the schematic is the 47µ from Q2 source to ground... There may be two electrolytic filter caps on some original units.
      +m

      Delete
    4. drdFX20 October 2013 at 20:52

      Check the original demo by PGS I think, there are some shots from the guts. Here is one picture (taken from that demo): http://members.upc.hu/dudas.csaba5/original_pcb.jpg
      I assume the fets are Q1 to Q3 from the upper right corner to the left at the bottom. Now if you check the upper right fet, there is an electrolytic above it. The biggest one on the left is the 470u filter cap (which is substituted with a 100u in your layout), the one in the middle is the 47u source cap on Q2 and I think the upper right one is a source cap on Q1 or Q3. From the size I'd say it is 10u or 22u. I could imagine that Brian changed the schematic a little, say a v2 maybe. Or maybe I'm completely wrong, but anyhow adding a source cap to Q3 and/or Q1 definitely helps.

      Delete
  16. Kramer8821 October 2013 at 09:06

    Thanks! :)

    ReplyDelete
  17. Billstein9 November 2013 at 07:59

    Hi all. Trying to get into this whole vero thing and built this up tonight. It works but sounds really fizzy. It biased fine, and the resistors are correct. Any suggestions where to look?

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  18. Jimijam19 November 2013 at 18:58

    I see FSB has the Velvet Fuzz schematic dissected so am thinking about using this as the base of that pedal and see how it comes out... Great Layout mirosol and hopefully a Velvet Fuzz will come up soon that fits inside at least a 125b enclosure :)

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  19. Unknown23 November 2013 at 19:35

    Mine doesn´t sound right. Mostly clean, only a little bit of distortion. Biased at 4,8V...

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  20. Unknown24 November 2013 at 17:01

    Wrong resistor, damn. Now it sounds as it should! But it´s too clean!

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    Replies
    1. mirosol24 November 2013 at 19:16

      Try to bias them by ear and with gain maxed.
      +m

      Delete
    2. Unknown25 November 2013 at 19:15

      will do, hope it´s hoter then...

      Delete
  21. Anonymous27 November 2013 at 10:24

    Did this and it sounds better now. But the trimmer from Q3 (in the lower right corner?) doesn´t change anything when trimming. There must be something wrong, have to check this. But perhaps I need a booster. Which one to choose, must be a linear one, want that sound but more distortion. Or I try the cap from Q3 to ground...

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  22. Iago26 March 2014 at 05:55

    Just finished this one. Sounds awesome. Biased all the trannies @ 4.5V. One the best OD's I've ever played with I'd say. I guess I'll just leave the "bass" switch engaged all time tho. Really liking the fatness. Gain is ok, probably just like the demos (I haven't checked them in a while)! It can do low gain quite well, up to a medium, compressed, plexi-esque (duh) OD. Not something you'd play metal with but for Classic Rock it's a killer. Thanks, Miro!

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    1. GeSi26 March 2014 at 10:31

      why not make the "bass" as standard and test some other caps to switch to?
      maybe something that gives nice sound with high volume on amp with rolled back volume on guitar and neck pu?

      i deffo gonna build this one!! cheers for the trimmers!! they sure give us more hope to score with our builds :)

      gotta love this place :P

      Delete
    2. Iago28 March 2014 at 03:41

      Yeah, the "bassy setting" might as well be my "stock" setting. I wouldn't add anything more to it though, the pedal sounds great like it is, maybe use a footswitch to change from bass mode (lead) to the actual "stock mode" (for rhythm). ;)

      Delete
  23. GeSi26 March 2014 at 10:20

    will we win anything by matching the fets for this circuit?

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    Replies
    1. IvIark26 March 2014 at 10:47

      Shouldn't really make a difference, the trimmers will allow you to bias unmatched fets as easily as matched. It's really things like phasers where matching is much more important.

      Delete
    2. GeSi26 March 2014 at 19:47

      thanks!

      i am almost done with this PlexiDrive, but lacks the 1N5817 :(
      any substitutions for that one?
      i think i'll jump over to the Fuzz Master until stuff arrives :)

      i can't see you guys making any money from this site!??
      you all should!! this place rocks! :P

      get some affiliate with Tayda or something and i'll support it :)

      Delete
    3. IvIark26 March 2014 at 19:59

      Try a 1N4001 or really any silicon diode will do, even a 1N4148. The site will never make anyone a millionaire but if you click on ad links or buy a kit from bitsbox or the soon to be announced US kit seller then we will get a contribution for that :o)

      Delete
  24. Iago27 March 2014 at 19:17

    This comment has been removed by the author.

    ReplyDelete
  25. Iago27 March 2014 at 19:18

    I decided to play with the trimmers a bit. Biased Q2 @ 3V or so. Sounds killer with the extra gain. This circuit really impressed me. Might make the bass switch a footswichable feature one day. Cheers!

    ReplyDelete
  26. GeSi3 April 2014 at 22:15

    i got only two J201 that bias 4,5V at 15K, third best biased 3,56V at 15K so i used the trimmer to get it up and gave it the Q1 position. many of my J201's needed 4,7K to get to 4,5V and that gives not a clone of the plexi-drive. in next Tayda order i order some more J201's. the pedal sounds VERY much like a JTM-45, it beefed up my Blues DeVille 410 on clean, so... it's gonna get boxed soon, killer sound :P

    next pedal to be built is MXR Distortion + :)

    thanks all at tagboardeffects, cool project!!

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    Replies
    1. Iago4 April 2014 at 22:43

      It's still a clone no matter the bias settings. Don't let Mr. Wampler fool you ;)

      Delete
  27. hangingmonkey17 April 2014 at 09:14

    Is it important to use matched 201's for this. What's everyone else doing?

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    Replies
    1. mirosol17 April 2014 at 09:57

      No. The trimmers are there to disable the need for a matched set. Each JFET can be biased separately with the trimmers.
      +m

      Delete
    2. hangingmonkey17 April 2014 at 10:49

      Thanks

      Delete
  28. hangingmonkey2 August 2014 at 04:29

    Wasn’t sure where the best place for pics are, Ive built a multi with 5 vero circuits from layouts from here with a relay switching mechanism from TH Customs with a 1 of X function. 1 of the circuits is the Plexi so I thought I’d post it in this thread. The others are MXR Dist+, TS9, catalinbread Rah and midifi fuzz gun
    .
    Anyway, heres some pics:

    https://www.dropbox.com/s/7d0lh6ou9m1nk1i/IMG_6029.JPG
    https://www.dropbox.com/s/kj892yoypwgkdxq/IMG_6036.JPG
    https://www.dropbox.com/s/ezppt8fhokqh7wz/IMG_6037.JPG
    https://www.dropbox.com/s/z35f9lxx821xoqj/IMG_6039.JPG
    https://www.dropbox.com/s/lnnchkh5dikfym7/IMG_6040.JPG
    https://www.dropbox.com/s/gxxsm8mlbp25k6y/IMG_6044.JPG
    https://www.dropbox.com/s/cayge6pxft1zei0/IMG_6046.JPG
    https://www.dropbox.com/s/tknok2p5cmjd2jz/IMG_6047.JPG
    https://www.dropbox.com/s/f0xxu2iko0vzqr8/IMG_6050.JPG

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    Replies
    1. Doron Barness2 August 2014 at 08:37

      INSANE !!!!! man.....in a good way...!!!

      Delete
    2. IvIark2 August 2014 at 11:03

      Awesome, great build

      Delete
    3. MAO3 November 2014 at 23:09

      Fantastic!
      How do you mount those LEDs without a bezel? Glue?

      Delete
  29. Unknown21 August 2014 at 11:55

    I have big crackling or "horn" noise here. I tried to bias by ear, 4 - 4,5 - 4,8 - 5. I cant make this one sound like it should. I always have big noise. Please help me... i'm working by 2 days. I'm goin' mad. I double and triple checked everything!

    ReplyDelete
    Replies
    1. IvIark21 August 2014 at 13:56

      It could be anything based on your description, we always need all pin voltages so we can see if something looks amiss.

      Delete
    2. Unknown21 August 2014 at 15:35

      Ok... I have this readings from left to right upper couple first, then the lower one:

      D 4.50 S 0.32 G 0.00
      D 4.56 S 0.37 G 0.01
      D 4.52 S 0.27 G 0.00

      https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-xpa1/t31.0-8/10620065_778718858837808_8846163737579090255_o.jpg

      Delete
    3. Unknown21 August 2014 at 15:46

      THE ABSURD AND INFAMOUS thing is that after i took these readings for you I closed the pedal, plugged it and it played perfect. After a minute of playing it began to crackle as crazy. Now if I open it i'm quite sure i'll find all the readings totally different from before.

      Delete
    4. IvIark21 August 2014 at 18:07

      Your voltages look ok and judging by the fact it started working and then stopped again it strongly suggests a bad solder joint or connection somewhere. You're really going to have to go over it with a fine tooth comb, reflow solder if necessary and make sure all the connections are true

      Delete
    5. Unknown21 August 2014 at 18:13

      I spotted something wrong on the switch. I used a SPDT as SPST. Now... when I engage it the voltage raises to about 8 volts. So... i cant get what's wrong. All the solder are good and i have no false contacts.

      Delete
    6. Unknown22 August 2014 at 16:47

      no ideas?

      Delete
    7. IvIark22 August 2014 at 17:03

      I've given my ideas. If it works intermittently then it has a bad connection somewhere or possibly an intermittent bridge that makes an occasional unwanted connection, but it's something that we can't diagnose for you unless we had the build in front of us.

      Like I said this is something that you have to go over with a fine tooth comb. Sometimes cold joints aren't obvious and so reflowing the solder may be necessary, especially around any connection that doesn't look perfect.

      Delete
  30. motterpaul13 September 2014 at 05:08

    I built this circuit and had a fair amount of success - but not complete so I hope people will bear with me on some questions. I thoroughly tested the circuit for layout, cold solder joints (did find two & fixed them) - slivers, etc.

    I am able to bias the J201s to 4.24 v. - But I am getting no gain.I get "tone" and can hear the pots and switch working, but its a clean guitar tone, no gain at all. So, two questions.

    1) I believe some of my J201s came from Tayda which I have heard are ?able. If they are not good, would I still be able to bias them. Since I can bias then, can I assume they are good? Or not?

    2) The 1uF Cap with no polarity. I do not have such a cap. (Ironically I just bought one to make the test box from last week). But I only had one. That box will be done by Monday, I hope. How critical is this cap spec? I tried using an electrolytic, tho I don't know which way to orient the +/-.

    I tried both ways and it makes no difference, still no gain.

    I know when my audio probe is working I make have better luck with this but if anyone can answer my questions now I would appreciate it.

    I also saw some people recommending tying some sources to ground with caps, but in those cases it was when they could not bias a J201. I am not having that problem. There was one guy who said he had the same problem as me - but if he fixed he did not come back to report how it was fixed (something that people should try to do).

    Thanks for any help at all.

    ReplyDelete
    Replies
    1. mirosol13 September 2014 at 07:40

      4.24V sound a bit low. Try tweaking the trimmers by ear instead of any particular voltage.

      1µ cap - plus side down.
      +m

      Delete
  31. motterpaul13 September 2014 at 19:57

    Just got this working a cold solder joint in first 1M R (sometimes you see them at different angles when you turn the board). Found it with an audio probe.

    Great circuit. The tone does not do a lot for me, the switch does far more. Together they give some variation. Varying the bias does more for the tone than anything. Lower V seems to mean more gain & noise, so it is a trade-off in there. But this is an ear-bleeding circuit just like a real plexi - one the best yet I have personally built from here.

    ReplyDelete
  32. motterpaul13 September 2014 at 20:53

    By the way, I socketed and just changed the 10n cap (103) to a 47n (473) - and it now works in the manner I would call a tone control. You still get all the highs but also a workable range of tones in between to a very mellow sound.

    ReplyDelete
  33. Doron Barness24 September 2014 at 14:55

    This comment has been removed by the author.

    ReplyDelete
  34. j7 December 2014 at 08:45

    Does the third lug on the tone control get connected to anything? Thanks

    ReplyDelete
    Replies
    1. mirosol7 December 2014 at 15:41

      It's not connected. If you want, you can chain the tone 2 with tone 3. Result will be exactly the same.
      +m

      Delete
  35. Doron Barness27 April 2015 at 19:32

    Great Great layout and a great sounding pedal whether you bias the JFETs at 4.5V or 5V.

    Thanks guys,

    http://fuzzquest.blogspot.com/2015/04/rocking-in-plexi-world.html

    ReplyDelete
  36. moos23 October 2015 at 21:43

    I had high hopes for this build but sadly mine sounds very clean compared to the demos. Wonder if it's something with the BF245As I used, they worked well in the Marvel Drive but not in this one no matter how much I twinkered those trimmers. Maybe a bad FET..

    ReplyDelete
  37. Unknown3 December 2015 at 00:27

    First I want to thank you Miro for this "handy" layout with trimmers. I made this and sound very nice! I didn't get much time to bias JFETs by ear. But i have one question: The original gain is just fine, but i'd like to get a bit more. Is that possible just changing some components? Cheers from Brazil!

    ReplyDelete
    Replies
    1. moos28 December 2015 at 21:36

      There's an aforesaid mod that you can add an electro cap to Q3's source to ground to get more gain, or playing with source resistors.

      Delete
    2. Unknown30 December 2015 at 03:00

      Cool man, it worked! I've tested with several cap values, like 1uF, 10uF, 47uF, etc..., but the result was always the same. I ended up using 47uF and a switch on/off to get the cap connected to ground when i want.

      Delete
    3. moos30 December 2015 at 12:49

      This comment has been removed by the author.

      Delete
    4. moos30 December 2015 at 12:50

      Great! Does it affect the tonality/frequency response? if so, how?

      Delete
    5. Unknown30 December 2015 at 13:55

      No at all, it just increase gain and volume a little bit, like a clean booster pushing. No squeal, humming or any other annoying problems. Nice and easy mod. ;)

      I tried add another cap from Q1 to ground, but this time the tonality change becoming too bright, and i didn't like it.

      Delete
  38. moos28 December 2015 at 22:04

    Tried those tiny MMBJ201s and yeah, they woke this thing up quiet much. The bass boost was too much for me and the lows overwhelmed everything so swapping that 2n2 cap to 1n really helped to get a nice tone there and to hear a bit more mids. Thanks for the tip!
    Any more components to change for getting more mids? Thanks!

    ReplyDelete
  39. Unknown8 April 2016 at 16:10

    Hi there, first of all thanks for this great sight. I'm pretty new at this and this site is invaluable. Built the triple wreck and its awesome.

    This build is not going so smoothly. I have breadboarded the above and biasing j201 is proving to be a challenge. The drains are biasing between 4.8-5.0v however the source voltages are very low all three around .09v

    Why would this be? My understanding is that they should be around .5v.

    Source resistors have been double checked and all are the correct values.

    There is no distortion. I have audio probed the drains of each j201 individually and biased until i heard clipping without the farting but it cleans up by the time the signal reaches the output.

    Any help would be appreciated.

    ReplyDelete
  40. John25 September 2016 at 14:39

    Great layout !!! The best diy pedal I've ever made ... sound much better with trimmers... although i adjust them only by ear (these one never lie) sounds very organic.
    It's the firSt time that I put my clean channel on with a smile.
    It's like it was a marshall that I've never had in my room.

    Thanks

    ReplyDelete
  41. John25 September 2016 at 14:41

    Great layout !!! The best diy pedal I've ever made ... sound much better with trimmers... although i adjust them only by ear (these one never lie) sounds very organic.
    It's the firSt time that I put my clean channel on with a smile.
    It's like it was a marshall that I've never had in my room.

    Thanks

    ReplyDelete
  42. Σταύρος21 February 2017 at 21:21

    This comment has been removed by the author.

    ReplyDelete
  43. estiven8 June 2017 at 03:33

    https://www.youtube.com/watch?v=P2LpG-3Rkyg pretty good

    ReplyDelete
  44. Unknown15 January 2018 at 14:14

    I built this thing yesterday and it will work when I first plug it in, then it loses gain until you have to really hit the strings to hear it kinda break through a gate. Any ideas? I spent a long time re-flowing all connections, and scratching out any bridges, I do think I will socket my jfets and try different j201s from the package of 50 i have

    ReplyDelete
  45. Percy Hornickel7 July 2021 at 15:40

    This circuit could be made using 2N5458 jfet and 5K trimmers. My build works perfect using this jfet. Drain bias 4.5V each.

    Later I changed trimmers for resistors (4K, 4.3K, 4.3K) according vth of each one too. Amazing sound.

    ReplyDelete
  46. oshun5 August 2021 at 08:06

    The Gain potentiometer works as a volume. Its like a booster on max and silence on min. What is the problem with my build?

    ReplyDelete
    Replies
    1. Percy Hornickel7 September 2021 at 02:08

      Mine worked the same with the first set of jfets I tried (2N5458), then I found K68A and after setting the bias (4.5V) the gain responce was so better, now I get clear signal with min gain.

      Delete
  47. Bucksears26 December 2022 at 01:18

    Anyone know of any way to adjust/boost the mids? I'd like to implement something like the mids toggle on the Mini Plexi Drive.

    ReplyDelete
  48. pavonepedalfx9 August 2023 at 23:12

    Ne ho realizzati due di cui uno qualche anno fa (e ricordo che suonava benissimo) e un altro di recente. Su entrambi ho apportato le seguenti modifiche rispetto al layout: sostituiti i J201 con 2N5457, sostituito il condensatore da 1uF con uno elettrolitico, sostituito il condensatore da 2,2 nF al centro con uno da 1,5nF e infine sostituito il condensatore da 10nF con uno ceramico. La distorsione generata mi piace ed é abbastanza grintosa. Tuttavia, ho notato che quello di costruzione più recente, mi sembra un po' troppo carente di toni bassi rispetto al segnale dry in ingresso. Qualcuno sa dirmi su quali componenti posso agire per incrementarli? Grazie a chi mi aiuta....

    ReplyDelete

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