Wednesday, 4 June 2014

Diefet - Diezel VH4S Simulator

With 7 pots this was never going to be put in a 1590B anyway and so I wasn't so concerned about keeping the size down, although I bet it could fit in a 125B and would be very impressed if someone did it. :o)  I think most people will opt for a 1590BB though.

This is a project from techniguitare which has gone through a number of revisions over the years, with this version based on their 18V version of the circuit.  Use the trimmers along the middle of the board to bias each JFET drain to half the supply voltage.  The bottom right trimmer seems to alter the frequency of a high pass filter after Q3, and so will cut some low end.  This wasn't in earlier version of the schematic which instead just had a 100K to ground, but I can't speak French and so maybe someone could tell me the reason for its inclusion.






42 comments:

  1. I quickly read a few pages of the thread at techniguitare.
    Basically the original version had a fixed 330k resistor instead of the 470k trimmer.
    The pedal sounded great at low volume but way too bassy at high volume, the trimmer is supposed to correct this as you desire.
    Here is an nice sounding sample :
    http://www.techniguitare.com/projets/DieFet/Diefet-V1-21-ThruVoxengoBoogexAmplitube.mp3

    Thanks for the layout ! :)

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  2. I missed a cut at the output capacitor, so get the latest version.

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  3. I ordered 4 days ago half a dozen of 125B..... nice :P

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    1. Cool. As you're the person I always turn to when it comes to how many rows and columns you can cram into the different boxes, do you reckon it will fit ok?

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    2. Yes, no problem. 125Bs are very deep, so you can place the jacks "over" the board, no need to save space for the vero, and 7 pots are easy too on a 125B.

      You have room even for a 2nd stomp if you want :)

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    3. Hahah, I was waiting for the Javi challenge. I was hoping he'd dare a 1590B. :)

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    4. Altho i wanted to see you do this in a 1590A ;)

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  4. You can VERIFY this, I just finished it. Deep and Precense goes ccw so just change those so is it ok =) And one more thing, theres no reason to feed it with 9v, it sounds so much better at 18v so I will remove the switch on my build.


    Cheers Mortua

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    1. Wow that was quicker than I was expecting! :o)
      Thanks a lot for verifying matey, I'll make the changes and tag it.

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  5. Nice one Mark, thnk you very much. On my list!
    Vince

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  6. thank you lvlark i have been looking for the right metal tone and this is it for me.does D5 have to be a 9V1 zenner? i only have 5V1 zenners will this work or will it alter the sound too much?

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    1. That's just there to protect the charge pump IC from getting too high a voltage, because depending on which one you use it will only take 10 or 12V. So no a 5V1 won't do because it will drop the input voltage too much and you'll only end up getting around 10V to the main circuit. But it isn't absolutely necessary, so you can omit it completely and the effect will work fine. Just don't put more than 9V into it (or add a 9V1 when you get them)

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  7. What is the 470k trim for just below IC2?

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    1. It allows you to cut some low end so gives you an opportunity to tweak the sound to match your gear if it's a bit boomy.

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    2. I've noticed that in the vid there's also a toggle switch called bright. As for the FET's, I take it they have to be matched as well?

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    3. I'm not sure what that switch is. There are a number of places where you could affect the brightness of the effect I suppose, but I reckon the EQ is comprehensively tweakable without adding anything extra. Maybe something like that would be useful if you used a Strat and a Les Paul, so you can easily switch between the two to get a similar response?

      No you don't need to match the JFETs, they're individually biased by the trimmers and so having them closely matched to each other doesn't give you a benefit. Better to save those ones for a phaser or similar.

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  8. What do you think about these:

    http://www.ebay.com/itm/10-PCS-ICL7660SCPAZ-DIP-8-ICL7660SCPA-ICL7660-7660S-CPAZ-CMOS-Voltage-Converters-/291159968176?pt=LH_DefaultDomain_0&hash=item43ca7c89b0

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    1. They look good to me and I've bought all mine as eBay cheapies. You're so well protected as a buyer on eBay that there really no risk in buying. Just stick them all in a socketed effect or charge pump you've built to test when they arrive and you'll know if they're all ok.

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    2. Anyone build this with success? Verified?

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  9. Just built this tonight and can confirm that this is a freakin beast. Also confirming that the presence and deep knobs are backwards.

    Another thing that I noticed is that unity gain for me is at around 2-3 o'clock. Don't know if going to a 250k level pot will fix this or not.

    With the deep control, I'm thinking of replacing the pot with an on/on/on switch with 0, 5k and 10k resistors. The knob covers a lot of range, but maybe 3 presets would be easier.

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  10. Does the 7660s mean this runs at 18v?

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    1. Yup. It does. The other reason any circuit would have 7660S is bipolar +/- supply. But in this case, 18V.
      +m

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    2. Thanks Mark.
      Will a (16v) 470u cap work or will it just go poof?

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    3. The 470u will be fine at 16V, it's the 100u next to it and the other 100u's that will need to be 25V

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    4. Done. Very nice. Room for an extra pair of sox in a 125b.

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  11. I finally got this working right with the second build. With seven pots and 5 trimpots - all of them interactive, you have to be sure you have this right. It is a very sensitive circuit - to biasing and pot positions. Even the TL072 - I tried to use an 082 and it changed the whole dynamic - the tone pots were completely different. These opamps are not always interchangeable.

    Anyway - the pedal sound pretty good. The first had very low gain and I don;t know why. This one is a lot better for gain although the gain pot has very little play. The circuit is farty by nature as the guitar dies out, but when you playing loud it sounds tight and very punchy. I would like to smooth out some of the gating effect - maybe a few different FETs will work better. I will report back.

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    1. Also - I just tried some PN4393 fet trannys in this, and it is an improvement. I had a feeling those 4393 were better than J201s - a little more gain (forward voltage?) - and they are available and not that expensive.

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  12. I didn't find this pedal to be farty sounding at all.

    http://youtu.be/f3k_WKAzksk

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    1. Once I finally got it all working it turned out to be crystal clear - no farting. I hasd tried grounding my volume pot to the board (a few different ways) but somehow it never sounded great until I grounded it off the board. Also, once I started the biasing with the 3rd J201 it got better. I don't know if i had other problems along the way but it sounds amazing now. https://soundcloud.com/paulmotter/diefet2

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  13. I love this pedal. I didn't win any awards for compactness in a BB, but sometimes easy to build wins. One thought though as a started doing the artwork for the box, shouldn't this be a VH4 without the S? I think the S is on the stereo model and not on the mono model.

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  15. Is there any chance that someone could trace the signal path here for me? I have been over this one a lot and I am sure that my board was made right and the components are in correctly. I have been probing for a couple of hours now and I am not getting signal past the first gain stage. I have signal through the gain pot and into the 3rd row from bottom up to the 220k beside Q2 but after that I have nothing. Bottom side of the 220K has signal but the other side does not. My circuit knowledge is shallow so I can not see where to go from there.
    Please Help!!!!

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  16. Oh and I replaced the 220K to be sure.

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  18. Hi,
    I have a few questions, on the 18V schematic there are listed 3x10uf 25v and 2x100uf caps, but on your vero schematic you entered 3x100uf and 2x10uf caps.

    Also, on the 18V schematic there is a resistor 10 ohm 2w between Diode 3 and diode 5.
    Could you help please

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  19. also missing is the diode 1N4004

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  20. I just received this pedal on trade and am questioning the bias of the JFEts. What is considered the "supply voltage"? Is it pin 8 of the upper left IC? Should all 4 JFET drains then be the same voltage?

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    1. Supply voltage is 18V.
      So, jfets should be set at 9-10V on the drain.

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  21. Just built this pedal. First time around I got bypass signal but nothing when the pedal was enagaged. Couldn't find the problem so I scrapped it and started from scratch paying extra care to make sure everything was correct. Same result, I get a bypass signal but nothing when the pedal is engaged. I rechecked the board twice, ticked off all the components, jumpers, cuts, pot wiring etc to the vero diagram and all is in order. Checking my input and output cables, when the pedal is engaged I get continuity from sleeve to sleeve but no continuity from tip to tip. I checked the voltages on the ICs and the transistors powering the pedal with a 9v power supply and they look OK (but I am really not sure what I am looking for, I can post voltages if necessary). Checked my switch wiring and that looks OK. Tonight, I tried to audio probe the circuit for a few minutes (as with the voltages I don't really know what I am doing here but I thought I would give it a go). Miraculously when I retried the pedal I suddenly got a signal when the pedal was engaged. But the gain is very low, like an OD instead of full bore like the Diefet is supposed to be. Anyone know what the problem could be?

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