Wednesday, 16 May 2012

Maxon OD820

Klon killer?  Some people think so, but whatever it's certainly a great sounding overdrive.

Info about the original from Maxon:

While many consider the OD808 to be the greatest overdrive ever created, Maxon is not a company to rest on its laurels. Instead of basking in the glowing praise, Maxon has focused on the user's feedback to come up with an all-new overdrive circuit that addresses the key shortcomings of other units - the result is the OD-820 Overdrive Pro.

The OD-820 was designed to provide a wide range of tube-amp overdrive tones as well as a transparent, hi-gain clean boost. As the name implies, the OD-820 was intended for use by professional guitarists with advanced playing techniques. The OD-820's expressive tone reproduces fingering and picking nuances with haunting precision, making the best use of any guitar or amplifier's character. With a full-frequency response, minimal compression and zero tonal coloration, the OD-820 won't mask a player's performance weaknesses like other overdrives can.

One of the key ingredients to the OD-820's amazing sound lies in its power section. While the OD-820 accepts 9 volts coming in, it then uses a DC-DC voltage converter (#MAX1044) to bump this up to 18 volts. This higher voltage allows for a more accurate, full-frequency reproduction of the input signal than other units can provide. This higher voltage also allows for more balanced powering of the circuit, providing stabilized positive and negative DC voltage to the overdrive, blend, and tone sections of the circuit.

Overdrive and Blend? That's right ­ the other secret weapon of the OD-820 lies in it's blending of distorted and non-distorted signal to create its massive tone. The OD-820's Drive knob does double duty, controlling both the amount of gain and the balance between distorted and non-distorted signal. Note that we said non-distorted signal rather than dry signal ­ this is because this signal is still processed through the tone section of the OD-820's circuit before reaching the output. So, at the lowest Drive settings only non-distorted signal is sent to the output, providing the OD-820's stunning clean boost tone.

Like the OD808, the OD-820 distorts signal in the amplifier section of the circuit rather than having a separate clipping stage, which provides a smoother, more realistic tube-like overdrive than other methods. The higher voltage supplied to the amplifier section provides slightly more clipping than the OD808 or OD-9. The OD-820 uses only JRC4558 op amps for the warmest overdrive tone possible.







And a version using a modified gain pot arrangement (described in the comments below), using two independent pots for the gain control, now labelled Gain and Clean and put together by John.  Increasing the Gain pot to 500K will give you quite a bit more dirt out of this version.



123 comments:

  1. i cant find any 2sk246 in my area. any alternatives?

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    1. I thought they may be hard to find, I bought 9 a while ago but don't think I've seen any since. But this is just an input buffer so use any JFET with the same pinout. The 2SK117 or 2N3819 will do the job (turned 180 degrees).

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  2. On the pedal description it says the voltage doubling circuit is from a MAX1044. but the layout lists an ICL7660. For some reason I bought a bunch of max1044's a while back. Can I sub the icl7660 with a max1044? I've tried looking around for this, but cant seem to find anything about it. what do you think?

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    1. Should be safe to use ICL7660. They should be equivalent.

      http://www.musikding.de/Active-parts/Transistors/Voltage-Regulators/ICL7660S::1132.html
      +m

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    2. You can. I'm wary of using the MAX1044 because the absolute maximum voltage is 10V which is too close to the supply IMO, especially with my daisy chain which puts out 9.5V. The ICL7660S is rated for 12V and so gives a little more capacity. Having said that, there is a diode in series with the supply to the voltage converter chip in this circuit which I assume has been put in to shave 0.5 to 0.7V off the supply just to give the MAX1044 a bit of a helping hand. So yes use that, but I'd suggest looking at the ICL7660S in the future. They're cheap as chips on eBay (I paid about 20p each for my last batch) and give you a bit more peace of mind.

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    3. The Musikding one is exactly the one, but if you get them from anywhere else never use an ICL7660, make sure it's the ICL7660"S" version. The one without the "S" has an oscillator that runs in the audio frequency range, which is why a lot of people had problems with high pitch squeals in their Klon builds.

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    4. pennies for the 7660s? really? i paid like $2 a piece for all these stupid max 1044s. do you have any layouts for making a voltage doubler for the max1044 or know any other circuits I can build to use these extra 1044's I have?

      Thanks a bunch!

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    5. They have the same pinouts as the ICL7660S, so you can use any of the charge pump layouts on here. Personally I'd consider using a 9V1 zener diode or a 9V regulator with it just to make sure you're not going to reach the 10V limit.

      Here is where I bought my last lot of ICL7660S from:

      http://www.ebay.co.uk/itm/251005037298

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    6. so if I used your layout for the voltage doubler would I use the 1n400x diodes shown on the layout and add to it the zener diode. placing it in series with (is it pin 5?) of the max 1044?

      Sorry for the need to have it spelled out!

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    7. Sorry I missed this post. No just put something like a 10 ohm resistor in series with the supply to the board, and then the 9V1 zener between the supply and ground rails with the cathode to supply, like this.

      http://www.reuk.co.uk/OtherImages/zener-diode-voltage-regulator.gif

      Then any voltage over 9.1V will be dumped to ground. You could even plug in an 18V power supply and know only 9.1V of it would be reaching the circuit.

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    8. Awesome! thanks for the help... just found this post again. So the resistor and zener needs to be the first thing the 9v rail hits? Like I could just add an extra column on the left side of the board... or maybe even put the zener/resistor on a piece of perf between the dc jack and the main board?

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    9. It doesn't have to be the first thing the supply hits, anywhere between 9V and ground will be fine, so yes if you have room for an extra column then that would do the trick, as would a perf daughterboard with the supply and ground daisychained from the main board.

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    10. I've been wanting to do this for a while... but now I've recently found that Zener Diodes are supposed to have the opposite end go to ground, or the schematic is opposite or something like that... with that diagram which side does teh end of the zener diode with the band around it go to? I wish I could just order some ICL's but I have like 10 max1044's to use!

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    11. Cathode goes to supply. Remember with a zener it allows current to flow in the reverse direction if the voltage is above its voltage rating (the breakdown voltage), so if you use a 9V1 zener with cathode to supply it will dump to ground everything above 9.1V

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  3. Hi...what you mean with gain 2-3...2-2 etc?
    Gain pot has only 3 points

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    Replies
    1. A dual pot has 6. Like this:
      http://www.ebay.com/itm/250983095772

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  4. Any successful builds? I tried it last night and no luck. I gave up and went to bed but Im going to comb through it again today.

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    1. Post the voltages you're getting on each IC and fet pins, and post a high res front and back pic if you can. I want to get this verified so I'll check it over and double check the layout. Cheers

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  5. Here are the voltages:
    IC1
    1-8.69
    2-8.12
    3-3.35
    4-3.95
    5-0
    6-3.31
    7-8.74
    8-9.49

    IC2
    1-8.75
    2-3.47
    3-0
    4-3.94
    5-8.74
    6-8.72
    7-8.72
    8-9.49

    IC3
    1-8.73
    2-2.10
    3-0
    4-1.5
    5-3.57
    6-0
    7-8.04
    8-8.73

    JFET (2n3819 with its legs bent to match the layout)
    S-.14
    G-4.40
    D-9.49

    Pictures soon

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    Replies
    1. Just had a quick look over your voltages and something is immediately shown to be amiss. Pin 5 of IC3 should be the negative of the supply on pin 1 and so should be round about -8.73V. That in turn via links should put very close to -8.73V to pin 4 of both the other ICs. So that to me looks like you've got a faulty IC3 converter chip.

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    2. Oh and just to mention, it could also be the caps connected to that IC, most notably the 10u between pins 2 and 4 and the 10u at pin 5.

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  6. not trying to hijack this or change topics but you might be able to help considering this uses a dual gang pot as well. just rebuilt a klon and when the gain is all the way down its muffled, but as soon as i bring it up from 0 the slightest, its clear again. what do you make of that?

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  7. You may have mis-wired it. The dual gang pot is used to turn one thing up and another down at the same time. Or two things up/down at once.

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    1. I wasn't sure of the gain pot layout because the schematic didn't show the lug numbering, but I based it on the PCB layout shown on FSB which has the 560R on lug 3 and lug 5 and 6 to IC1 pin 1. Are you getting something out of it and does the problem seem related to the gain pot or is it totally silent?

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  8. Hey man! How could i do a circuit to convert the 9DC from a boss transformer to 9VAC? That's for a Whammy.

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    Replies
    1. You'd need some sort of power inverter which I suspect woud be a lot more trouble than it's worth.

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    2. DC Power Supplies are AC to DC convertors. It would be silly to convert it back to AC. You need to buy an AC power supply for the pedal or install a step down transformer in your whammy and run a 3 prong cord from that to the wall, but as Ivark said, thats too much trouble. Just spend the 20 dollars and get the right power supply.

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  9. It's just the gain pot. Volume stays the same just get super muffled and I have to bring the gain up a tad for it to open up again. It's the Sabrotone Klon vero layout. Pot is wired exactly how the diagram says. Says its verified. But It's got me wondering. Is my gain pot bad? I mean from how it sounds when the gain pot is all the way down its using your signals tone right and the more gain less of your clean signal goes through. So it sounds like its cutting off the clean tone when the gain knob is all the way down.

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  10. Ivark, as far as the 820 goes, the pedal just hisses and none of the pots change anything when its turned on. Tinnedman, you should probably talk to the sabrotone dude about your issue. He might have some insight into his layout.

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  11. Well it was more of a general dual gang pot wiring question. Considering this pedal uses a similar design, just wondering it it sounds like its miswired.

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    1. Not sure to be honest mate, but if you're not sure then desolder and measure the resistance between the wipers and both outer lugs to check the taper looks ok during rotation, and you're getting the right values. I know a few people who have build Harald's layout so it must be good, and that leaves build problem or part failure.

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  12. "the pedal just hisses and none of the pots change anything when its turned on."

    this is the same issue I am having.

    Any luck Writer?

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    Replies
    1. Can you post a front and back pic and the IC voltages

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    2. Sure, first time measuring these things, but here is what I get:

      IC1
      1. 8.35
      2. 8.18
      3. 40.2
      4. -1.5
      5. 8.97
      6. 8.29
      7. 4.05
      8. -0.2

      IC2
      1. 8.09
      2. 8.2
      3. 0.9
      4. -1.7
      5. 8.97
      6. 8.07
      7. 8.07
      8. 8.08

      IC3
      1. 8.09
      2. 4.02
      3. 1.8
      4. -46.6
      5. 8.08
      6. 5.5
      7. 2.37
      8. -0.8

      2SK117
      D. 4.88
      G. 4.08
      S. 8.96

      I used solid wire so I had to removed some from the board to get a good shot of the top.

      Pics:
      http://fearedandloathed.com/Images/BYOC/820a.jpg
      http://fearedandloathed.com/Images/BYOC/820b.jpg
      http://fearedandloathed.com/Images/BYOC/820c.jpg
      http://fearedandloathed.com/Images/BYOC/820d.jpg
      http://fearedandloathed.com/Images/BYOC/820e.jpg

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    3. Are you sure about those voltages? I've double checked your placement and cuts and it all looks good to me, but IC3 pins 1 and 8 are directly connected because there is no track cut between them (as it should be), so I can't see how you can have 8.09V on pin 1 and -0.8V on pin 8. Also the drain of the fet is sat directly on the 9V rail, so I can't see how you could only have 4.88V on it?

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    4. will check it again later today...my DMM sucks...need to get a new one.

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    5. Ok. Problem is me...and my numbering/labeling of the pins :)

      I switched out the 7660S with another just in case too

      Corrected Readings:

      IC1
      1 8.34
      2 8.16
      3 39.8
      4 -1.9
      5 -0.4
      6 4.03
      7 8.27
      8 8.96

      IC2
      1 8.08
      2 8.18
      3 0.8
      4 -1.9
      5 8.05
      6 8.05
      7 8.05
      8 8.95

      IC3
      1 8.08
      2 4.03
      3 1.6
      4 -19.4
      5 -0.8
      6 2.44
      7 5.47
      8 8.08

      2sk117
      S 4.88
      G 4.07
      D 8.94

      pin 3 on IC1 I have checked like 10 times...and its like 10 times higher than Writer's IC1 pin 3.

      Appreciate the help!

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  13. Those IC3 voltages are still so weird. I use that layout all the time to make a negative voltage so I can use a 0V ground with PNP fuzzes, in fact I've got one in front of me now in a Buzzaround, and have never had voltages like that. The only difference in this scheme and the one I use frequently is the diodes to pin 1 & 8 and pin 5.

    I've been over the layout loads of times now and can't see anything wrong, but this is one of those effects that for some reason, despite it sounding really great, I can't seem to find any other layouts and only 1 schematic which I honestly don't know whether is verified or not. I have got a couple of decent gut shots though so I think I should be able to trace it through myself just to see if there is any issue with the scheme. So put it to one side for a while so I can get that done and cross check everything.

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    1. One thing I will add though is that there is definitely some sort of grounding problem. IC1 pin 5, IC2 pin 3 and IC3 pin 3 are all connected to ground, albeit through different links. But that means there is still solid copper between them and so there's no way they should all be different voltages. That to me suggests there could be a cold solder joint at one of the points of ground maybe. You do have both double links up that left hand link chain don't you? How are you connecting ground with your offboard wiring, and are you getting 0V at all the expected points, negative DC socket, and the input and output sleeves?

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    2. Guess what? FIXED IT.

      Thanks so much man. You got me to look at IC1 pin 5 and I noticed a sliver of copper left in the cut. I went in and cleaned up all my cuts and it fired up.

      Literally did this 5 mins ago, so I haven't used it much, but it sounded good to me.

      I think it's verified :)

      Keep up the great work. Love your site.

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    3. Fantastic. Let me know what you think of it after a bit of playing time. This is definitely next build for me.

      I was reading something about it on a forum before and someone mentioned hissing. If you get some then increase the value of the 20p between IC1 pins 6 and 7. The value used doesn't really do much because it cuts treble way beyond the guitars audio frequencies, but if you put in something like a 220p instead it will cut at a more useful (lower) starting point and should tame any hissing.

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    4. Sounds really, really good. I haven't heard any hissing, but I'll keep that in mind if I do :)

      Here are a few pics:

      http://fearedandloathed.com/Images/BYOC/OD820a.jpg
      http://fearedandloathed.com/Images/BYOC/OD820b.jpg
      http://fearedandloathed.com/Images/BYOC/OD820d.jpg
      http://fearedandloathed.com/Images/BYOC/OD820e.jpg

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    5. That looks awesome, thanks for the pics. This is one of those pedals that I'm actually excited about building and that doesn't happen to often with me. I heard a demo a few years ago and loved it and was very close to buying it a few times but never did in the end, mainly because I use a rack tray and so am limited for space and didn't want a big pedal in there, but also because they're almost £200 here and I always think twice before paying that amount for any pedal.

      The thought of having one in a 1590B makes me happy :o)

      Delete
  14. Hi, i`m still a novice at this so i could very well be wrong but i noticed from DrRJE`s pics that he has a 16v 470 cap in there (couldn`t see the rating on the rest) i thought it was a general rule to use a minimum 25volt rating for caps on builds running from 18 volts, possibly writer`s problems could be down to under rated caps. Just a thought as i said, i could well be wrong.

    ReplyDelete
    Replies
    1. You're right but this doesn't actually run off 18V, it just creates an 18V swing (+/- 9V). That cap sits between ground and -9V and so it would be fine to use a 16V cap.

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  15. Im going to go over mine again or maybe I'll just build another board since Dr. got his working.

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  16. And it was just the transistor. I used a 2n3819 but once I put in an mpf102 it worked. Sounds great. Now I have two since I built a second one.

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  17. are there any other substitutes for the jfet used in this circuit? I dont have any of the ones listed as subs... no 2n3819 (which apparently might not have worked according to above) or the listed ones...

    i do have j201, 2sk117, 2n5457, 2n5854, some mpsa's, bc550... sorry i'm not too familiar with fets still... need to hit the books a lot more before i can really get along in this world!

    Thanks a bunch! I'm gonna start and try to finish this tonight- so if anyone's out there some help would be greatly appreciated!

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  18. Just use the 2N5457. That has a pinout of GSD from top to bottom with the flat side to the right, so you'll need to insulate and twist over the source and gate.

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  19. Oh just noticed you said you have 2SK117's, just use those turned 180 degrees to the layout.

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  20. thanks lvlark! Now I just populated the board and realized the circuit is asking for 250k dual pot. I only have 100k dual and 250k linear regulars. Would a 100k dual work in place with some mod or would 250ks somehow?

    ReplyDelete
    Replies
    1. Well if you used the 100K dual it would work but the problem is that you wouldn't get as much gain out of it. You could in theory use just a 250K pot but the only way you could do it would be if you ignored the Gain2-2/2-3 and Gain2-1 connections completely and instead soldered a 250K resistor between the points on the board where those wires are supposed to connect (IC1 pins 1 & 2). The single 250K pot would then connect to the Gain1-1, 1-2 and 1-3 points and perform the "panning" function between the lower and higher gain paths through the circuit.

      The problem with this is that the transition between minimum and maximum gain wouldn't be as smooth and the dirt would kick in much earlier, but the extreme settings of the Gain pot would sound identical as if you can the 250K dual in place.

      It's certainly worth experimenting with both to see what you think, and you can always order the correct pot later if you want to. I got some from Tayda for just a couple of £s.

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    2. thanks a bunch! I'll try it while I wait for a 250k pot!

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  21. Managed to stuff this one in a 1590B sized box. Didn't realize how tall the dual gang pot was until I tried to fit the board in on top of it... wasn't going to happen. Ended up turning the board upside down, and somehow making it fit in there, but I would never do it like that again. One thing that frustrates me is that even with builds that don't have dual gang pots, both styles of pot dust caps (plastic from smallbear, and rubber from mammoth) stick up too far to allow the circuit to sit on top of them. Have you guys seen any low profile pot covers or have another way of keeping the board from shorting on the pots? Right now I am using half a playing card to insulate between the board and pots in my builds...

    ReplyDelete
    Replies
    1. I use sticky-back velcro on the back of the board and the back of the pots to keep the board in place and have never had a problem shorting anything out. Mounting the board upside down is definitely the way to go with anything bigger than maybe 18 or 19 rows, and also when multiple toggles are being used which can also get in the way.

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  22. anyone got gut shots for an original? I'd like to see the component side so I can use all the correct tants and carbon films for tonezzzzz!

    tonez

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  23. Pics of the original: http://ohzobitobyte.seesaa.net/article/267419858.html

    ReplyDelete
  24. This works for me and sounds really great. Only one complain, and I think it might be just mine, but even with the volume cranked up all the way, it isn't exactly all that loud. This was confusing especially given the charge pump being here. Is there something wrong with my build? If so where should I look?

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  25. just finished mine and I love it. for me, it fit easily in a 1590B. as far as its output level, it's not the loudest pedal that I have but it can go way past unity gain even with the drive set at the minimum.

    pics:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Maxon/OD820-01.jpg

    internal:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Maxon/OD820-02.jpg

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    Replies
    1. Great looking build John, and still one of my favourite overdrives ever!

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    2. thanks Mark. yeah, it's a reeeeeally nice overdrive. some even refer to it as a "Klon killer". ;-)

      thanks for posting it!

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    3. Man! That is super neat!
      How do you print white?

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    4. You can get white on clear labels for many of these labellers.

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  26. I just made this pedal born on 8/20!
    I like how it sounds, it is very quiet and is perfect for what I like in an overdrive pedal - I have a klone and I like this one better. Cannot wait to use this one in the band!
    couple of pics! Thanks lvlark!
    http://i145.photobucket.com/albums/r233/jimijam_photos/820g.jpg~original
    http://i145.photobucket.com/albums/r233/jimijam_photos/820f.jpg~original

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    Replies
    1. Excellent job, thanks for the pics. I prefer this to the Klon as well.

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    2. Thanks IvIark~!
      That 10uF cap that connects to ground and D4 - I originally had it connected to the D4 row and the one just below it and not to ground...
      I was on autopilot by the time I got to that cap and did a 2 row span LOL Fired the pedal up and nada. Quick spot check and I saw the error I made... wooops!

      Delete
  27. Is this a hard build? I've never built a pedal before, but I love the 820. Would really love to have one in a 1590B box. Currently using a Sparkle Drive for my TS tones, but would much rather have an OD-820.

    Should I try this build?

    ReplyDelete
    Replies
    1. You should familiarize yourself with the build method and components first. I think this is a bit big and hard project to start with. Meaning that if you run into problems, the debugging process may be too much.
      +m

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  28. Finally got around to building this today and I didn't expect much as I fell for the hype of the Klon and was disappointed but this thing not only kills the klon but buries it!. Absolutely stunning effect. I was going to do an A/B comparison with an original but they kept stalling on an expected delivery date so I cancelled the order. I wont bother ordering another as this one is perfect... dare I say it even makes my Zen sound lifeless!....

    ReplyDelete
    Replies
    1. Agree with you completely mate, definitely in my top 2 and probably my favourite overdrive. Opinions obviously differ with effects and some work better with certain guitar/amp combinations, but this one just hits that sweet spot for me.

      Delete
  29. hi.
    can I use an 18v charge pump, with proper cap values on this build?
    jeff

    ReplyDelete
    Replies
    1. It already has a charge pump and is working with 18V. See your post in the Klon thread.

      Delete
  30. Hi all.
    Are 1n914's ok to use in the 820?

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    Replies
    1. On the bottom strip there is a cap labeled 220n that looks like a ceramic.
      Will a box cap of 220n work or should I use a couple of ceramic values in parallel to get 220n?

      Delete
    2. Use anything ceramic or poly will work fine. I only showed a ceramic cap because that was the best symbol to use in the software for a 2.5mm pitch. Personally I'd use a box cap and bend one of the legs back and out again to the correct pitch.

      Delete
  31. Hi all.
    I just finished this and used 2, 250K lin pots for the ...clead/drive tones and it rocks!!
    The amount of control over the drive tone and clean tone is very detailed. I am probably going to put 500k pots on and see if it gets even better. Very nice build. I have a Maxon 820 OD Pro and this build is in a 125B box and sounds better with the seperate drive/clean pots.
    Thanks for the work Mark.
    Jeff

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    Replies
    1. Thanks for the feedback on the pots. I often think with dual pots performing different functions that you could be missing out on something good by not being able to control them individually.

      Delete
    2. You guys have definitely convinced me to build this after reading your comments. I'm just unclear on the separating of the dual gang into two separate pots. I'm assuming the drive is for gain. From reading the company description above, I'm gathering that the other side of the dual gang is a blend control for clean and gain. Is that correct?

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    3. The first gang of the pot pans between the first opamp stage (a gain stage with diodes in the feedback loop) or bypassing it through a couple of RC filters to the second opamp stage. So yes, when the gain of the opamp stage is greatest, the panning side is directing the signal through that stage. And inversely when that gain stage is at its lowest setting the panning gang directs the signal to bypass the stage and go straight to the second opamp.

      This will be fine for the vast majority of cases, but there are some people (particularly bass players) who like a clean blend with dirt pedals, and so I think it would be useful to separate them because then you could have the gain high in the first opamp stage, but panning 50/50 so you are getting clean signal through too. And the opposite way again, it would be nice in a lower gain setting where the dirt is more subtle, to direct more of the signal through it to make the overdrive clearer rather than bypassing it.

      Separate pots just opens up a few more options.

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    4. That was a very clear explanation - Thanks! Separate pots it will be then. Back to the parts boxes....

      Thanks again

      Delete
    5. Don't necessarily stick to 250K either. If you use a 500K (or maybe even 1M) for Gain2 you'll get a lot more dirt out of the first opamp (if that is your kind of thing). And you often see a 100K pot performing the panning function of Gain1 like in the Klon. 250K may be a happy medium but you may get more out of the pedal when you're not restricted by the dual pot requirement.

      I definitely think I'd go 500K and 100K and I probably will when I build the 4 knob version :o)

      Delete
    6. Well, you certainly won't hurt my feelings with a bit more dirt...or even a lot for that matter.

      On with the separate pots and altered values. Maybe I'll beat you to the build, but probably not.

      Jeff - cheers for the separate pot verification.

      Delete
  32. I just finished building my second. on this one, I used separate pots for the 250K dual gain pot. what's weird is that both of them add distortion (just different 'flavors'). i rewired the new 'clean' control and swapped lugs 1 & 3, and changed the Gain pot to a B500K and now it works properly. i like the pedal even even better than the stock one now!

    here's the modified vero layout of IvIark's:

    http://johnkvintageguitars.homestead.com/Effects/Fuzz-ODs/Maxon/Maxon_OD820-mod.png

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    1. Nice one John, I'll add it to the main post

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    2. Got this one finished yesterday ( 3 weeks later - so slow...). I try to keep my expectations at bay when I finally go to plug in a new build because there is so much hype out there. This one exceeded my expectations. This is not your average TS sound. Full and rich in harmonics. Loads of gain - I used a 1M for the gain pot. Not a ton of volume change with the volume pot so you really can't really use it as a clean(ish) boost. I may have done something wrong but I read the thread at FSB and someone mentioned that there's not a lot of volume boost from the volume control. No complaints though - if I want a clean boost, I'll use a boost pedal. This one just sounds great.

      Mark - you mentioned using a 100k instead of the 250k for the clean pot. Can you tell me what effect that would have over the 250k? Getting ready to build another immediately and I might swap that value out depending on the effect...

      Thanks John for the modded layout - that kept me from gooching my gain and clean pot connections.

      Thanks

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    3. The reason I mentioned the 100K pots was because I'd seen that value perform the same function in the past and so would expect it to do the job adequately. I've got tons of 100k pots but not so many 250K so it was more about using something most people will have to hand instead of having to order something in specially. All that pot does really is direct the signal through the opamp for its dirty mode, or around the opamp for clean mode and I think it's one of those functions where the value doesn't have to be precise for it to do it's job as long as it's "big enough".

      It's all thinking out loud really, the real proof of the pudding is in the eating and I haven't tried it yet myself. I'd be interested in hearing how you feel it compares though.

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    4. Cool. I'll check it out. I really like this pedal. I'm not throwing my Gainster and Clay Jones in the bin, but it may be a while before I plug them in again :)

      Thanks for the help as always sir!

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  33. Hi all.
    I have now built three of these with different pot values for gain and clean and I think they're the best overdrive.....hell they're the best tone monster out there. Couldn't use it (one) for metal but it's like Billy Gibbons and the Bixonic..put enough of em in line and you can get anything you want..
    I do have a question. When the tone knob is turned past 80% a noticeable hiss arrives. I used a 50k pot and still got the hiss. Any ideas how to get the full treble range with no noise. It's very usable but I would like to fix it (them). Every one I built does it.
    Jeff

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  34. Have just finished this effect. Sounds GREAT, maybe too bassy for my taste, but I have to admit that is one of the best sounding overdrives that I have listened or played.

    The funny thing comes when i checked the voltages to see if they were correct (+9 /-9) , and have never seen such a weird voltages:
    IC3
    8.88
    4.41
    0
    -4.39
    -8.76
    4.81
    4.47
    8.88


    IC1
    0
    0
    0
    -8.09
    0
    0
    0
    9.55

    IC2
    -0,027
    0
    0
    -8.10
    -0,09
    -0,09
    -0,03
    9.55

    s 7.15
    g 2.40
    d 9.55

    Funny shit. The effect sounds quite well, but the measures are pure crap :P

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    1. That is weird. If I saw those voltages I'd have bet good money they effect wasn't working

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    2. Just gessin'. This pedal uses a +/-9v power supply to generate a 18v potential, instead of a doubler to get 0-18v. So vr is referenced at 0v, ant

      Perhaps this is the reason of my readings....

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    3. Yes very true mate, it has a 0V reference point so it makes sense

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    4. Anyway, I first checked the effect on my Valvestate, and liked what I could hear, but, I've been tryin' it with the Laney, and OMFG....

      Have to give a longer and more in deep tryout, but as someone told before, this little board kills, buries and I would say, rapes the Klon (and i really LOVE the Klon).

      Will have to check John's mod with two pots instead of a dual gang. In the Klon is not a good idea, but I trust John's opinions. Sometimes i like the results, and some others, are not my cup of tea, but always worth a try.

      J.

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    5. I've been taking a look to my Mutron III voltages, as it uses too a bipolar +/-9volts power supply, and can now confirm that my previous measures are correct. The reference pont is 0 volts, so, nothing to worry about.

      After a few hours playing this pedal, I can tell that is really awesome. Not to be uses as a clean booster as many people do with the Klon, but on the other hand, the drive sound, KILLS the Klon's overdrive.

      Have to check both on the same chain, with the Klon pushing and the 820 as main overdrive.

      J.

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    6. Agreed completely mate, I'm not a great fan of the Klon as an overdrive anyway, this one to me just sounds perfect and definitely my favourite overdrive.

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    7. The two knob version really is still one of my favorite builds from here. I used a 1M for the gain pot. I can get anything from cleanish grit to low growl to pretty aggressive OD. And if you are in a place where you can turn the volume control up, it adds sort of a fatter OD to the already driven tone. And with my P-90 equipped guitar, i won't even start....

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    8. Hey, I ordered some B250k double gang (linear), and have received W250K double gang ones (W tape)!

      Didn't even know that it existed, have to check 'em this evening with the 820 with 4 knob that I built!

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    9. Mark I'm really glad to hear you love this pedal as much as I do. I'd be tempted to build one, but I bought the real deal many years ago, before I ever got into pedal building. Since the day I brought it home, it's been my all-time favorite overdrive. Heck, I may end up building one, just to have the option of a smaller enclosure (the original is like a cadillac... really luxurious, but the size of a yacht!)

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  35. Hey Mark I'm looking at this and I see a pretty simple way you can improve this layout by moving D3 so it isn't connecting under IC3

    You can swap the jfet and input cap to each other's columns, and then move the diode under the input cap's new location. Obviously you'd have to move the cuts to make it work, but you have enough space to do it no problem

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    Replies
    1. Yes that would make more sense, I'll update it. Cheers

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  36. Ooh nice. And you even gave some extra space between the jfet and electros by moving that 10k :D

    Thanks Mark this layout is a masterpiece!

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  37. Increase the 100k resistor to the immediate right of IC1 for more volume. I use a 220k which gives unity at around 12. I also use a W20k for the tone as it gives a much more gradual sweep. I think the W20k is used in the Tubescreamer, too....

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  38. gotta try out some w20k's. anyone tell me which of those electro's need to be over 18v? does the 220uf need to be? could i sub a 100uf 25v? Thanks!

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    Replies
    1. the voltage rating can be anything, as long as it's high enough not to be fried. personally all my caps are 25V, and up. i try to get the smallest caps with the highest voltage i can.

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    2. There's no 220u :o) If you mean the 470u then it is sat between ground and -9V so even a 10V cap should be ok (but preferably 16V). And yes it's just a supply filter cap so 100u will probably be fine.

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  39. Hey guys, just finished the 4 knob version. Works and sounds nice, thanks for the layout!
    One thing is a bit weird though.. I have to crank the tone pot practically all the way up to get the treble similar to the bypased signal.. If I turn down the tone pot to say 3 o clock the sound gets quite dark.. Is this the way it should work?

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  40. Hey there just curious! If there is an 18 volt charge pump does that mean we need to up the cap volts? Is 16 volts going to cut it on the electrolytics? Thnx!

    ReplyDelete
    Replies
    1. Pump's not used as a voltage doubler, but it produces a +9/-9V swing. So you'll just have both, +9V and -9V present, which looks like 18V through the eyes of the opamp. 16V caps can handle that just fine.
      +m

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  41. Hmm, mine (clean and gain mod) sounds nothing like the video above. It's bassier and sounds more like a fuzz...

    I've substituted a 500kB for the clean, and a 5.6pf (well, that's what it has marked on it!) for the 10pf. I'm also using a 2n5457 with twisted leads. All these subs are because that's all I had around.

    The clean pot is working more like a gain, while the gain doesn't appear to do anything. The tone pot is acting as a volume, cutting it to nothing with less than a quarter CCW turn from max.

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  42. Hey sorry to bring up an old project, but I've recently built this (the gain & clean version).

    I get a high-frequency whine/oscfillation at all settings... could it be that my voltage doubler is wrong?

    I'm using a TC7660SCPA, which apparently is meant to be ok for power... did I order the wrong IC?

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  43. I'm having quite a bit of trouble getting the negative supply voltage to work correctly. I've built this part of the circuit twice now, and I can only seem to get -3volts. I've used different caps, checked all of my orientations over and over, knifed everything that I can, and checked both a MAX1044 and a 7760s. I'm generally a good trouble shooter, but I am rather stumped this time. Any tips from anyone?

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  44. i can't get 20pf capacitors.
    can i use 22pf one instead of 20pf?

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  45. This comment has been removed by the author.

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  46. Just finished mine yersterday, I think the owner will be pleased. Nice pedal! Did the 4 knob version, really tweakable that way. I wouldn't exactly call it a KLON killer, but it's very good, wooly ,plushy sounding. Btw, if some of you experience weird high end fizziness with the tone knob at max, or boosting an already ovedriven amp,almost into oscillations with this, try a number of 7660S-s from your batch,some don't exactly cut it, some are perfect. The pedal works perfectly.
    Here are some pics, thanks again guys! You rock!

    http://hgecontraptions.blogspot.ro/2016/03/maxon-od820-clone-with-clean-and-gain.html
    https://www.facebook.com/hgecontraptions/posts/696165800526239

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    Replies
    1. Here's a sample also: https://forums.rgc.ro/index.php?app=core&module=attach&section=attach&attach_id=259696

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  47. replacing 7660 to max1044 without mods is ok?

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