Monday, 5 July 2010

MXR Dist +


76 comments:

  1. Hi,

    I'm wanting to give this one a try but the 1N270's are hard to come by and pretty expensive in the UK

    Can I use any other germanium diodes? if so, any recommendations?

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    1. Hi
      I think 1 N 34 A sounds cool or Try red leds they sound cool in this circuit ...and gives it a lot more output

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    2. Hi, Yep I put 1N34A's in and they do improve the sound, a little more organic sounding :)

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  2. Try whatever you can get hold of. I've bought 1N34A and 1N60 off eBay at quite reasonable prices. Or you could even try a Schottky diode like a BAT46 or 1N60P. They have a similar forward voltage and so will get you in the same sort of ballpark.

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  3. Ahh cool, I've seen 1N34A's on the bay.. Just bought some BAT46's for when I try the Purple plexi so I'll throw them in :)

    Also that Karaoke has grown on me... sounds really good as a dirty channel boost... It doesn't thin out like Ts9 types do..

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  4. My 1uf's are radial, what would be the orientation?

    Thanks

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  5. The right hand one is negative to bottom row (ground), the one just to the right of the IC is positive to pin 6

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  6. Super fast! cheers Guv'nor :0)

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  7. Just put this together and I get very low distortion right up until the very end (of turning gain knob) then full gain when gain knob is at max?

    I have used a 1m linear... (B1M)

    The only difference is that I used BAT46's

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    1. Sounds like reverse log may be better suited to the gain control. It's definitely linear in the schematics I did this from, but I've just had a quick look in a couple of threads and there are some people who have suggested reverse log.

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  8. Ok what value of reverse log would you suggest?

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    1. I've got 3 schematics for it, 1 calls for a 1M, and the other 2 say 500K. It's probably that they're both right and both values have been used over the years.

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  9. Just to add, there is little to no volume boost either, which I see on the threads is common.

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    1. Germanium diodes and Schottky have a low forward voltage and so a lot of the signal is dumped to ground. Silicon diodes or LEDs should make it louder. Hmm just read something that suggested log rather than reverse log. Do you have any log pots you could test it with?

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  10. I've just put a C500k for gain - Much better.. seems to reduce highs a little when lowering but that may be just the nature of the distortion.

    I have some 100k logs, maybe try that for volume?

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    1. Yes still try the 100K log just to see what you think. I've seen someone else suggest 100K is a good value anyway so it would be interesting to see what you think

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  11. Ok, The 100k log seems to make no or very little difference? ... You get just of unity when the volume is of full... still a gradual volume sweep though...The pedal does sound good! and I don't see it as an issue as this type of pedal should be cranked anyway.

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    1. Sorry, should read 'You get just ABOVE unity....

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    2. Thanks for the info Vince

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  12. No worries, thanks for the layouts :0)

    I've been looking at a few demo's and I think what I have now (100k & C500k) sounds pretty typical of this pedal so it's all good.. as with this demo, he has to push the volume up to get unity and the sound he gets is spot on to what I'm getting..

    http://www.youtube.com/watch?v=_y21D8OHSKY

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  13. Hello,

    I was wondering if you could tell me exactly how i could attach a sp3t switch and also and led to the circuit.

    I am in the process of building a synthesizer and I would love to be able to have this as an on-board effect but would only be suitable if I could have the effect bypassable.


    Hope you can help,

    Jordan

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    1. Sorry, I meant spdt.

      Jordan

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    2. Sorry I missed your post. Well you could switch the effect with a SPDT switch but it would mean that the input wouldn't be switched and so always in circuit which isn't ideal (although MXR and I think Dunlop still do exactly that sometimes). Ideally you want a DPDT switch to bypass the effect, then both the input and output can be switched for a true mechanical bypass of the circuit. If you want LED indication as well then ideally you would want a 3PDT switch and you'd wire the switch as shown here:

      http://tagboardeffects.blogspot.com/2012/02/offboard-wiring.html

      You could use a DPDT switch with LED indication if you use the milennium bypass way of switching. That can be seen here:

      http://i76.photobucket.com/albums/j6/IvIark_2006/Layouts/Vero/MilleniumBypass2.png

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  14. Just finished this one. First i built it to the specs on the layout, but with those i got really poor control and even with two pots, only decent sound came out with both of them maxed.

    So, i swapped LM741 with LM301 and that gave the distortion more strenght. I'm starting to understand why LM741 is not very highly valued in any electronics communities... :)

    For controls, i swapped A10K volume pot for C10K, and B1M drive pot for C500K.

    Might say that it's a bit modded, but it's good basic distortion.

    Thanks Mark once again.
    +m

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  15. Which way are the diodes facing? is the white band the cathode?

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    1. Yes the white band is the cathode in that symbol, but as there is one in each direction it doesn't matter which is which.

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  16. Would it be possible to add Mark Hammers "Stupidly Wonderful Tone Control" (http://www.muzique.com/lab/swtc.htm) to this? and if so, could someone help me out. I'm a newb and having trouble understanding how this would work.

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    1. Check this to determine component values of your filter - there is a paragraph called "High and Low pass filters":
      http://www.generalguitargadgets.com/richardo/distortion/index.html

      Let's assume that you have 4K7 for R1, 220nF for C1 and a B10K pot.

      Take the wire that goes from board to volume 3, cut it from the middle and solder that 4K7's other lead to the board side of the wire. Then solder that other lead to the B10K pot's lug 1. Next, solder B10K's lug 2 to other lead of 220nF cap - other lead to lowest row of the board, the right hand side. Then the B10K lug 3 to volume 3. And finished.

      I strongly suggest using breadboard to find out suitable values for R1 and C1. Article above has the formula for caltulating the frequency points...
      +m

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    2. Thanks, already built one, gonna do another one with a different op amp, diodes, and probably a tone knob, see how it comes out.

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    3. You'll get much louder effect with silicon diodes like 1N4148 or 1N914. Or try red, yellow or green leds for heavy distortion. As for opamp, in my opinion, LM301 sounds much wider and heavier in this. And don't forget rev. log pots for better control.

      And if you experiment with tone control, let us know the values you used :)
      +m

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  17. One more question, could I use 1n914's in this? and if so how might that change the outcome?

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    1. Yes you could use them no problem. The output will be louder with silicon diodes and it will change the character of the distortion. It's one of those where you really want to maybe socket and test for yourself to see which type you prefer.

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  18. Ok so I'm waiting for a few parts and keep having ideas for mods. I'm thinking of using both germanium and silicon diodes and switching between the two via a DPDT switch. So where on the board would I take the in and out leads to the switch?

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    1. Not a bad idea..

      Use the right hand side, seventh and ninth rows.

      And if you do that SWTC, please share your values for cap, resistor and pot.
      +m

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    2. Ok, so I went ahead and just breadboarded the whole pedal. I'm using a TL071 op amp because I had a few lying around, sounds pretty good to me, then I used the c500k for the gain and a a10k for the volume, seems like I get a lot more volume now. As for the tone control, my best results have been with a 10k pot, 68n capacitor, and a 560ohm resistor. It definitely cuts out some of the high end right off the bat, but it also takes some of the self noise with it which is nice. I'm using 1n34a's for the testing. if anyone else try's the tone control let me know what values you use.

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  19. mmmm i build this proyect and sounds like treble boost i change a couple caps and the resistor 4k7.. I found a schematic, original layout and still the same sound some body to gimy some advice or wiring the pots or some information i use a UA741CP IC i change the pots for 500k drive...50k vol...mmmm the same sound like treble boost,,I like the soud but not for distortion +.. help please......

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  20. built this exactly to the layout and experienced a condition described on earlier posts where the gain would jump significantly within the last couple of degrees of right rotation. Based on the discussion above, I substituted an A500K for Gain, and an A100K for Volume. The A500 was wired in reverse for reverse taper and it works and sounds much better.
    Another forum suggested that the MXR Dist+ was the best circuit for using a wide variety of diodes or LED's. Consequently, I built a Diode/LED Ferris Wheel using a 12 pole rotary switch, socketed the diode pads on the board and plugged into the sockets. With this setup, I now have 12 different combinations of distortion, sounds great! It is not in a case yet, but here is what it looks like on cardboard mockup.
    http://s786.beta.photobucket.com/user/petevig/media/IMG_1876_zpsb84039cd.jpg.html

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  21. Built this to spec last night. Yeah that gain knob is pretty useless. To be honest I think it could be removed because flat out is where this pedal comes into its own anyhow. Great old school distortion though and worth the build for any 70s rock fans.

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  22. Is this spec'd to the vintage scrip Distortion +, or the newer Dunlop model? I've tried both and the vintage one sounds MUCH better... hoping I can build it!

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    1. This is the old one. I personally still prefer all/any 250 version(s) over this...

      Some time ago i got a dunlop made one and it just sucked. Which is funny as it is 1:1 with original (germanium diodes, LM741 etc..) Only difference between original and dunlop reissue is the PCB. Original is made like most of the pedals are always made - while dunlop reissue has massive ground fill that seems to run over strips on some spots. Which shouldn't affect it, but i can't see anything else changed in there. I modded my dunlop reissue a bit.. Input cap to 100n and gain filter (47n here) to 220n. Also swapped the clipping germaniums for two pairs of 1N4148. It is now loud and very articulate. Not to mention that it is now a real distortion. It gets over unity with gain at zero easily and the gain pot is now very useful.
      +m

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    2. I actually used to own a script one but it stopped working, and I miss it a lot! How do the 1N4148 diodes affect the tone? I really liked the filthy drive that came out of that script Dist +. Also, I'm relatively new to pedal building and I noticed that this version doesn't have any bipolar caps, can you replace bipolar caps with polar caps and the tone stays the same? Not sure if this is a stupid question...

      Thanks for answering!

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    3. No. It's not a stupid question. And yup. At least some original units have tantalum 1µ caps for vref filter and output. For this layout, you would have positive down on the left one and positive up for the right. However, i do think there won't be any tonal differences between the types - non-polar poly, aluminum electrolytic or tantalum.

      About the clipping.. Well. Standard silicon signal diodes will have slightly different clipped wave form. While they might sound a bit harsher, they will give a lot more output as they dump less signal to ground compared to Ge diodes. You could always take DPDT On-On switch and wire its lug 2 to 7th row and lug 5 to 9th. Then take two Ge diodes between lugs 1 and 4 - and two (or four, two in series and two of those in parallel) 1N4148s between lugs 3 and 6. You could even use DPDT On-Off-On and wire it up the same as above. That way the middle position would act as a diode lift and pass all the gain without clipping it. If you're not familiar how different diode clippings sound, you should definitely try that.
      +m

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  23. Hello I would like to comment on my build. I have tried all the different changes on this page and I get the following:
    - I have tried all the combinatios with 1M and 500K pots for drive and 10K and 100K for volume and I cannot really hear a difference. Is the 1M supposed to give more distortion than the 500K? In my case it doesn't. Also, changing from linear tape to audio taper improves the response very very slightly. In both cases you only get some noticeable effect very near the end of the range.
    - For the diodes: it is true that silicon diodes increase a bit the overall level, but not that much. Using a level meter it was a bit less than a dB, a bit more for 5mm red leds
    - I did find that TL071 sounds smoother than the LM741. At least my 741 is marked as ua741, I don't know if it is the same thing.
    - removing the diodes you get distortion too, which i can imagine is from cilipping in the opamp. The diodes add flavour to this (and more distortion of course), but at least in my case they are not responsible for all of the distortion. I have checked the build and it seems ok, I would like to know if this is the same for more people.

    I have tested this with some high outupt dimarzio humbuckers, not sure if I am feeding too much signal to the circuit and that is why the different change in componentes give me very similar results. I may put somewhere audio clips with the different options if someone is interested

    best

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  24. Hello. Just finished building this one and now I'm having two problems:

    - Distortion is AWFUL, cant play any chords and it sounds more like just playing with a really bad amplifier with gain&vol pots on max -.-
    -Distortion only works at last ~3% of drive pot's range (using same values as in diagram)

    I'm using similiar components/values, though diodes are 1n4148.


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    1. 1N4148 for diodes makes it pretty much OD250 :)

      But those pot values and tapers are wrong. If you have any, try 500K rev. log for gain and 100K lin for volume. I bet those will cure it - and it'll sound like a killer.
      +m

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    2. ...or just solder a 560K resistor between lugs 2 & 3 of the gain pot. That'll help out a lot too.
      +m

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    3. Hello my friend. Thanks for the reply, I'll try different pots and let's see what happens ;)

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    4. Well, soldering that resistor didn't change a thing...

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    5. That's strange.. You did solder it between lugs 2 & 3?
      +m

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    6. Any reference voltages to share ? I was wondering if there's something wrong with my opamp.

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    7. Changed the gain pot to A500K. Distortion works better but is still kind of lousy, doesn't sound like it should at all

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  25. just built it and it sounds awesome! but the distortion knob only delivers distortion on the last end of the pot. i will try different setups when i get more pots from Tayda, then i'll box it.
    kinda like putting Randy Rhodes inside a 1590BB enclosure ;)
    AU741CP gave a more fat sound so i went with that one for now.

    i think the Wampler Plexi.Drive and this one covers a lot so i will go building a fuzz now, Silicon Fuzzmaster from Lovepedal :)

    another great project from tagboardeffects... thanks :P

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    1. Yes you may find you get a better gradual control of the distortion if you use reverse log.

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    2. i did some test without the pot and sent wires to breadboard and swapped resistors just for fun. and the distortion came at 1k ohm and was nice and loud at 150 ohm.... and schematics says 1M (?)

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    3. Yes, that makes sense. The distortion will increase as the value between the top of the 4K7 resistor (connected to lug 3) and ground gets closer to zero. 1M does seem very high but that was the value in the original. Reverse log will mean the resistance between that resistor and ground will reduce more rapidly because of the taper and so should be more useful.

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    4. okey, thx

      i saw, while surfing the web, that AU741CP was in the old script logo pedals, i just swapped in and out of the ones i got and that one sounded absolutely best in my rig, cool :P

      i run my Fender Blues DeVille 410 with 2 matched JAN Philips 7581A tubes, so this pedal becomes a wild beast, bedroom window shakes at volume set at 2 :o

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  26. what kind do you use foot switch sir? DPDT Momentary

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    1. If you mean for bypass, then latching DPDT if there's no need for a LED. If LED is required, then latching 3PDT.

      Also, i'd highly recommend using C500K or C1M pot for the gain. Linear doesn't work very well.
      +m

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  27. tnx a lot sir mirosol for your advice

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  28. Thanks so much for the layout.
    Check this out: I called my version STRAT-O-DRIVE
    I use a 5way switch to switch between different diodes.
    http://mace.nemethmusic.com/strat-o-drive/Strat-O-Drive.jpg

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    1. Thanks :-)
      Next is the LES PAUL-O-DRIVE ;-)

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    2. That's one of the coolest looking pedals I've ever seen!

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    3. Thank you :-)
      Check out my Version of the Dunlop Cry Baby
      http://mace.nemethmusic.com/fx/dunlop-cry-baby-3.jpg

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  29. Wow. That looks great! I really like the little scratch plate piece you used

    Now you have me thinking.. I could probably cut that type of material really neatly with my small router with an angled bit :0

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  30. Hello I rebuilt an old mxr distortion + out of order with most of his original components , following your layout and it sounds pretty good now , but a bit noisy. Is it possible to find a way to tame that noise?
    Thank you.

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    1. I'm guessing you are using the circuit with a power supply and not with a battery.
      You could add two things that will affect the amount of noise. Wire a 100µ (or bigger) cap between supply and ground. Negative lead to ground, obviously. And then take a 100R resistor in series with the +9V supply wire. Those do it.
      +m

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  31. Hello and thank you for your answer.

    I tried 100u ( directly on DC power jack , negative lead to ground and positive on supply ) and 100R in series with +9v supply wire , also with 470u and 470R resistor and it doesn't change nothing. I also tried a +9 battery supply but the sound came strange. Maybe I did something wrong.

    Cheers,

    Dave.

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    1. At that point i would measure the power supply and double check everything on the build. Current limiting resistor should affect noise a lot, as should power filter cap..
      +m

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  32. I found an interesting schematic about you explain :

    http://www.diystompboxes.com/pedals/ps.html

    That might be useful to other users , I'm gonna retry tomorrow .

    Thanks.

    Dave.

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  33. Hi!
    I love the sound of the original layout, well C500K is much better gain control. But I want it louder, any ideas except diodes or booster? And I tried the other IC too, liked the original better.

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    1. external boost circuit was actually very good idea + good reviews :)

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  34. Hi, I would like to know which capacitor changed to give more bass, and the 1u is a 103 tantalum capacitor? can someone help me please? thanks.

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  35. Hi I built this but only the clean signal comes through it seems gain pot not responding, I tried to change it to 500k...nothing happened. My voltages are: 0,01;0,01;1,52;0;0;7,84;7,21;0. Could you please help me? Thanks

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