Friday, 1 March 2013

Maxon OD808 Reissue

Info about the Maxon reissue:

Originally released in 1979, the Maxon OD808 was one of the first tube-amp overdrive simulators to hit the market. Its smooth, creamy crunch tone caught on quickly, and helped to launch a long line of predecessors as well as imitators. Today, the OD808 design is without a doubt the most used, most imitated and most lauded overdrive circuit of all time. The reason for this is simple ­ tone. Simply put, the OD808 provides the natural, mild overdrive of a tube amp without sacrificing your guitar's original tone. In addition, it can be used as a clean booster to provide increased gain without compromising the sound of your amplifier.

The secret behind the legendary "808 tone" lies in the amplifier section of its circuit. Rather than having an amplifier stage followed by a clipping stage, the Maxon OD808 uses a signal-distorting diode (Panasonic #MA150) that is located in the amplifier stage's negative feedback loop (which also contains the JRC4558 IC chip). Therefore, the Maxon OD808 distorts signal in the amplifier circuit itself which yields a smoother, milder, more natural sounding distortion than a separate clipping stage. This is also the reason that the IC type used in the circuit has such a large impact on the unit's tone. Maxon developed this unique design more than 20 years ago, and while it is commonplace nowadays, back then it was an industry first.

It should be noted that the Reissue Series OD808 uses different output resistors than the original version. After the unit's initial release it was discovered to have a high susceptibility to noise due to static electricity buildup. To improve performance, the positions of the output resistors on the reissue OD808 were reversed and their values increased in order to reduce noise levels. This circuit change has no audible affect on the sound of the unit, save for reducing the noise levels.

Whether it's used as an overdrive or a booster, the Maxon OD808 is the closest you can get to the classic sounds of 1970's rock guitar in a compact effect pedal.







Geiri's build of this layout:





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26 comments:

  1. Definitely going to build this. Played one and loved it. Classic sound of course, but classic for a reason..!

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  2. Is this circuit the same as the Ibanez Tube Screamer? It looks like it to me.

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    1. It's almost exactly a TS9, but it was requested so thought I'd do it anyway :o)

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    2. Thanks Mark :D I really need to build the two versions to compare them.

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  3. You can do a mod with a DPDT to switch the 2 resistors that are different, no need to build a whole new pedal.

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    1. No, the original OD808 is different. It has two ICs rather than one IC and two transistors. Both versions are on here

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  4. This ones good to be tagged! Thanks for this one, I had just had a request from a friend to build him a Tubescreamer style pedal so everything seems to have come together nicely :D It's going in a box with a dirty boost I've been trying to 'design' and I use that term incredibly loosely.

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    1. Excellent cheers matey

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    2. No problem, to be honest the first TS clone I built was a Lovepedal Eternity and I could never really see what all the fuss was about, I'm glad I was forced into this one because it sounds excellent. Is this maybe because of the buffer, or just the component changes? If it's the buffer, I wonder what swapping it out for a Klon or Cornish buffer would sound like? Hmmmm.

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    3. The buffer means that signal hits the gain stage in a predictable way no matter what was before it in the chain, the Eternity and similar pedals that just removed the buffers have to be more inconsistent because the way they behave is then determined by what is before them in the chain. The Klon buffer in particular has its own colouration and so there may be some differences if you used one in place of the transistor buffer, but I don't expect the differences to be too extreme.

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    4. Ah, thanks for the explanation, maybe I'll try it at some point in the future and find out. Perhaps that's what helped it to play nicely with the booster I've tried in front of it, mainly I was just surprised at how well it gelled with my amp when it was pushing it, I find with the Blues Junior it doesn't really like being pushed too hard, I've tried quite a few boosters and they seem to come out too muddy when the pre amp volume is set too high, with the Maxon circuit I can crank the pre amp to full to give a nice bluesy distortion (it's still pretty mellow, not like a cracked Marshall etc.) and the TS works really well with it, the Eternity never seemed to work that well and suffered from that muddiness. I never really bought into the whole Tubescreamer as the holy grail of tube amp boosting but maybe I've been a bit harsh.

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  5. I just finished this one, and it is very low-level, and I can't hear it at all unless I aim my amp to 8 of 10 level.
    I already tried the faults manual, but haven't found anything suspicious.

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    1. Maybe try checking the resistor values, that's what it usually is for me if I've got too little gain/volume.

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  6. hello guys, i tried to build this but i get nothing but silence and a little heat from the IC and some capacitors.
    can you help me debug my circuit?

    http://www.2shared.com/photo/1Sx8LHTy/_DSC2392.html
    http://www.2shared.com/photo/aZ0E2i2m/_DSC2394.html

    i also don't know if i did something wrong with the dpdt to jack connections

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    1. If you measure the transistor and IC voltages that will give us a good clue

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    2. i had the capacitors in wrong polarity because they were marked on their negative marker. i changed them and the IC too. but its still the same. it kind of works but on really low volume

      on what voltmeter settings to I measure the transistors?

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    3. Well the voltages should be between 0 and 9VDC so whatever your appropriate DC setting is.

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    4. i put it on DC voltage, at 2 it just said 1 so I put it on 20v.
      upper left transistor from E to C 4,84v - BC 4,05
      the other transistor gives 5,13 and 3,11

      i don't know how to measure the IC i put the red cable to the right side and the black to the left, checking the opposite legs it gives 4-5.8 volts. and it also heats up to some level when the circuit is on.

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  7. Does the 100u,is a filter cap? If not, where is the ground (i mean near the 9V)?

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  8. Thank you guys! allways wanted to built one of those.
    Sounds very very nice!

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  9. Hmm build this and everything works except for the gain knob. I checked the wiring and the vero for shorts. Tone and Level seem to work fine but gain does nothing at all... some ideas?

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    Replies
    1. Having the same problem as you, did you found any solution tho this yet?

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    2. I just build a new one which worked from the start... Don't know what the problem could have been :/

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  10. This comment has been removed by the author.

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  11. I received this kit and it came with the 2 prong DC power jack. Which of the two prongs is positive/negative? Is the long prong positive?

    thanks

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  12. The Tone control for the most part is too dark and at 4-5 oclock cleans up. Although I tried a lot of different pots (B20k, A20k, B100k, A100k) I did not see any difference, tone control for the most part is too dark. Can someone help me spot the tone circuit on the vero so that changing some values would work? Thanks.

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