Thursday, 1 March 2012

BJFE Model H

Great sounding pedal designed to emlulate a HiWatt amp, and so one for you Who fans out there.  Again this was an awkward one to keep the width down, but it will fit nicely in a 1590B.

Video of Geiri's build of this layout:



Update (23rd March 2012): Missed cut, use this latest layout


52 comments:

  1. am i going to be the first one to make this? i love this pedal

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    1. Depends if you get started before my workshop is ready. :o) Chances are you will though, I've got a ton to build and it's about time I started verifying some of these myself!

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    2. ha i have this bad habbit of starting another pedal while im waiting on parts to finish another. on my bench right now is deep blue delay with the tap, the hearthrob trem, another klon, and this haha

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    3. Cool. I've got so many to get through when I'm up and running again that it isn't funny. On the bright side it means that I'll have an in-progress board permanently in a PCB vice with all my components within easy reach and soldering irom always setup and ready to go, so I can be doing little bits all throughout the day (or at least whenever I nip to my workshop for a crafty cig! :o)

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    4. haha between the solder fumes, paint fumes, and the cigs i hope to finish all these pedals before its too late hahaha

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  2. Buulding this next week. 21st birthday funds going to my new addiction to building pedals ha thanks again for the awesome layouts and detailed help to all my newb questions. Learning a ton and improving my tone. Couldn't ask for more haha :)

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  3. Ah, so it's not just me then! I swear that the goofs at Golden Virginia must laugh their cocks off when they see you've posted a new layout on here, their sales increase ten fold! Smoke em' if you've got em'! :0P

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  4. Do it while you can still afford to more like. Any more budgets like that and I'm going to give up and cost the government a fortune in the tax they won't get off me any more! :o)

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  5. You can mark it verified friend. Sound amazing. The only thing I noticed (which could be my mistake) but the drive pot is reversed. As in turning it down increases the gain. Again that may be my bad. But the pedal sounds amazing. My new favorite overdrive. It's so punchy and responsive and smooth. Thanks for the awesome layouts man!

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    1. Excellent, thanks mate. The drive is probably me not you, unfortunately the pot numbering isn't always mentioned on the scheme so I end up doing the best guess. If you swap the 1 and 3 wires around it should reverse that for you.

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  6. Yeah tried that last night. Fixed the problem. Everything works and sounds really good. Absolutely my new favorite overdrive/distortion. The thing just sounds downright mean :)

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  7. Great website! I need help with this one though. I checked and double checked. All parts and solder joints are fine. I noticed that when engaged, the volume is bairly audible. When audio probing it, the volume drops significantly at the end of the 47nf that joins with the gate of the N-JFET at the bottom of the board. I did replace all the 2N5952's with 2N5457's because I didn't have the 2N5952's on hand. Is that the problem? Are the 2N5457's not a good replacement?

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    1. The pinouts of the 2N5457 is different from the 2N5952. They'd all need turning 180 degrees.

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  8. I did that already. All flipped.

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  9. I did that already. All flipped.

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    1. I am a bit biased about the JFETs, but they never seem to bias correctly with me. If you have more than 6, you could try to swap & probe 'till you find the ones that work together..
      +m

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    2. Edmund, did you get it working somehow? I have the same issue(s): very low output and no distortion, but the pots are doing what they´re supposed to do. 2N5952 are on their way.....

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  10. The JFETs for this circuit need to be matched?

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    1. I don't know whether they're matched, I haven't seen any measurements, but I will say that JFETs seem to be much harder to just replace with another type of JFET than people may be used to with bipolar silicon transistors. There are differences in the specs between the 2N5952 and the 2N5457, and so they may not be biasing correctly. We know the layout is verified, so if everything else looks good then the JFETs would certainly be something I would consider a likely culprit.

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    2. I didn't mean that they should be mathed. It's just that the cutoff voltages may vary so much, that some may cut off with the voltage that is meant to pass throught them. If your JFETs just cut off too early, there's no signal travelling through them at all. Cutoff voltage isn't normally an issue with bipolar transistors. JFETs are not as stable on the specs as bipolar transistors. And then they need to be biased correctly for operating the right way.. Geofex' article explains this a bit:
      http://www.geofex.com/article_folders/fetmatch/fetmatch.htm

      Matching is usually necessary when using JFETs as variable resistors, like in 45 and 90 phaser.

      In my experience, only time i didn't have any problems with JFETs was the time i built Ruby Red booster - i used matched set from musikding in that one. All the others.. Even with verified layouts, i couldn't get some to work untill i measured and swapped the JFETs around for a very long time. I'm no expert in these, but this is how they have worked for me so far...

      If they didn't sound as good as they do, i wouldn't even try to build anything with them :)
      +m

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  11. Any idea on where to add another pot for the "treble" in the 4 knob version?

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    1. There's lots of ways and places you could add a simple high pass filter (a pot followed by cap to ground before the Volume control could do the job) but I haven't seen the guts of the 4 knob version or a schematic so I don't know the exact way Bjorn has done it. I'll keep my eyes out though and if I can get a decent gutshot that I can interpret from, or find a schematic for it then I'll add a new layout for that version.

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    2. In this link http://3.bp.blogspot.com/-A61n73ryRjM/TxHtk2yZ9BI/AAAAAAAAAiA/8GBs9JPfJ_E/s1600/bjf_Model-H.png there is a layout from Freestompboxes with the treble modification. "Replace R15(1.5k)with 5K pot/trimmer for the treble control".

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    3. I thing that it's the resistor (1.5k) on the left of the third transistor...

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  12. I built this one today. the drive pot is shown backwards on Mark's vero. lugs 1&2 should go to ground and Lug 3 to the circuit board. also when mine didn't work at all I realized that the 2N5952's all had to be rotated 180 degrees from Mark's diagram. that fixed everything and it sounds awesome.

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  13. BTW, the DSG labels on Mark's vero are correct, it's just that a 2N5952's flat face is the opposite of the diagram.

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  14. Done!

    pics:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BJFE/ModelH-01.jpg

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/BJFE/ModelH-02.jpg

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    1. Thanks John, I'll correct the layout

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  15. I can't seem to get this to work - I've built dozens of pedals, but this one has low output and tone doesn't seem to work. Also seems to be slightly mixed with dry signal. I've checked all components, grounds, circuit seems correct, layout, etc. Do I need to match my 5952s? I'm a bit stumped -

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  16. Hi guys,
    is it normal to have the led on the left (D1) always on when the IC is connected?

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    1. Sometimes they light sometimes then don't depending on the voltage through them, so it's nothing to worry about.

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    2. Ok here's my update; I've breadboarded the original schematic (which is the same of this layout), and what I've figured out is that if I any cap from 47pF to 80nF connecting pin 1 and pin 8 of the IC, the overall sound produced by the circuit is veeery noisy and oscillating; this noise decrease once the capacitance increase.... I've found the 220nF is the correct cap (between pin 1 and pin 8) to cease any unwanted noise, but the sound is muddy...
      I'm using the BF244 instead of the 2N5952... but i don't think this could make a difference like that!

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  17. Could I use 180k or 220k resistors instead of the 200k resistors?

    If so, which value would work better?

    Thanks

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  18. Just finished building the Model H tonight and to my great surprise it fired up for me the first time! That hardly ever happens, especially on a complex circuit like this.

    I made sure to use all of proper resistor values, using some metal film resistors where necessary (my metal film resistor assortment had, for example, the 200K value whereas my carbon film assortment did not). I also used 5mm LEDs with about 1.8 V forward voltage from Radio Shack. I didn't have an second C50K for the tone so I used a B50K - you definitely need the reverse log, but the linear will do for now.

    I played it for an hour and it sounds REALLY good (and loud) - definitely one of the best amp like distortions I've built. I noticed that it still has some grind on the lowest gain setting, but that's OK - this is rock and roll pedal for sure. The distortion/breakup is really smooth too, not grainy like some op amp-based pedals. I think the Marvel Drive just got some competition!

    This one is will be boxed very soon...thanks again for a great layout.

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  19. I've built it and when turning the drive knob up it starts making this loud squeal.

    Any idea what's wrong?

    Thanks

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  20. Mine works perfectly (and will work more perfectly when I get some C50K pots from Small Bear :).

    Tell us more about the squealing. How far do you have to turn the gain knob until it squeals? Anything else not seem right (e.g. excessive noise)?

    One thing to check is the orientation of the diodes. The layout has a minor error in that it shows a "stripe" (indicating + side) on the LEDs both on the same side, although the + is marked correctly as being on opposite sides. Make sure your two LEDs have + orientation on opposite sides as indicated. This along with 100 pF cap should keep it from squealing (and I assume you're using the correct chip, a CA3130E).

    If that's not it, then you'll have to post voltages.

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  21. The LEDs and chip are correct. The squealing starts when you turn up the Gain about a quarter.
    When it's bellow that everything is fine with no noise or anything like that.

    Where should I check the voltages? The chip or the transistors? And on which pins?

    Thank you for your help :)

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    1. Try moving the wires about in the box, especially creating more separation between the input and output wires. Just see if that affects the amount of oscillation you're getting.

      For voltages check all transistor and IC pins, measure DC voltage between the pins and ground and post the list.

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    2. I rewired the pots and that took care of the problem.

      However, the pedal doesn't have a lot of gain on tap, I noticed the leds don't light up, before with the oscillation they did.

      And the tone knob works like a mids knob, scooping the mids as you turn it. Is this normal with this pedal?

      Thanks

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    3. Here are the voltages:

      Transistors (from left to right):

      D- 6.67 S- 0.8 G- 0

      D- 7.3 S- 6.2 G- 0

      D- 0 S -0 G- Can't get a reading

      D - Can't get a reading S- Can't get a reading G- 0

      IC:

      pin1- 77mv??

      pin2- 4.2

      pin3- 4.1

      pin4- 0

      pin5- 77mv??

      pin6- 4.2

      pin7- 8.3

      pin8- 4.4

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  22. This comment has been removed by the author.

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  23. Hi Dudi - Mine has plenty of gain and the LEDs light up strongly. I'll check my voltages when I get a chance. Don't worry about Q3, Q4 - they're being used as clipping diodes I believe.

    Do you have an audio probe? Maybe you could probe the signal path and see if there is an obvious problem somewhere.

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    1. Hi Frank, just tried probing it, didn't help much... The other weird issue is that I have tons of volume available on the level knob, and in the videos it doesn't seem to have that much volume. I can't turn up the volume past quarter way or it would be way too loud.

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  24. The fact that you have a lot of volume and the LEDs are not lighting up would suggest to me that the LEDs are not working correctly. If they were working the volume would drop as the signal is clipped and you would see the LEDs light up with your signal. Also, Q3 and Q4 are wired as clippers so check those jfets. Make sure they are oriented properly.

    Beyond that check all connections and make sure you don't have any solder bridges or cold solder joints. If you can upload some pictures that would help. Here is the schematic for your reference.

    http://revolutiondeux.blogspot.com/2012/01/bearfoot-fx-model-h.html

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  25. Here are the voltages for my working Model H. Q3/Q4 omitted as they are used for clipping.
    (All values in V)

    Source voltage = 8.8 (battery)

    Q1 D = 3.15, S = 2.27, G = ~0
    Q2 D = 4.48, S = 1.90, G = ~0
    IC
    Pin 1 = 0.066
    Pin 2 = 3.98
    Pin 3 = 3.90
    Pin 4 = 0.0
    Pin 5 = 0.067
    Pin 6 = 3.98
    Pin 7 = 8.00
    Pin 8 = 4.15

    I hope this helps. Looks like your IC voltages are fine but the jfets are quite different.

    BTW - the LEDs actually don't strongly light unless you turn the gain up. But you should see them flash when you play. I have picture of my board if you want me to upload that to the Forum/Chat.

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    1. Thanks Frank! Here are pics of the board:

      https://onedrive.live.com/?cid=EFEF1BBF45E3CCE3&id=EFEF1BBF45E3CCE3%21207&authkey=%21AJc_6KhWbMTWE3k&v=3

      https://onedrive.live.com/?cid=efef1bbf45e3cce3&id=EFEF1BBF45E3CCE3%21206&v=3&ithint=photo,jpg&authkey=!AEibSJxk8oyowps

      I did suspect the transistors so I tried changing them and that didn't help.

      I got them from Tayda, maybe I got some fake ones??

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    2. Dudi - Check your off-board wiring. It looked to me as if lug 2 of the Drive pot (which connects to lugs 1 of Volume and 2 of Tone) did not have a path to ground. If so, add a wiring to ground it to lug 1 of the Drive pot. Hopefully that fixes it. That would explain the funny voltages for Q1 and no gain.

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    3. Hi Frank, it does a path to ground with the blue wire from lug 1.

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    4. (i connected lug 2 to lug 1 on the gain pot)

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    5. OK. Couldn't see it in the photo. Check it for continuity (along with the rest of the off board wiring). You never know where a cold solder joint will show up. If none of that pans out as the issue, then I can only suspect a bad part, solder bridge, or cold solder joint somewhere on the board. I would focus in and around Q1 and Q2. Good luck!

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    6. I did go over the board with a magnifying glass and didn't spot any solder bridges or cold solder joints. Could the transistors be the issue?

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    7. Well, try substituting other jfets for Q1 and Q2 (I doubt Q3 or Q4 are the problem). And I assume you have used your multimeter to do continuity checks? For example, check your track cuts and make sure there is no continuity across any cut.

      When it comes down to it, to debug a circuit, you just have to check everything - components, voltages, continuity etc. Eventually, you'll find it. I probably can't help further beyond this. Hope you can get it to work - it's a great overdrive/distortion!

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