Thursday, 2 March 2017

Earthquaker Devices Black Eye

From the source:

This ll discrete, MOSFET based circuit provides nearly 30db of unadulterated clean gain boost with a minimum amount of tone coloration. Note that you can also use this as an attenuator by turning the Boost knob counterclockwise away from the noon position. It can also be used as a powerful buffer with an input impedance of around 5M Ohms and an output of around 1K Ohm, best used after your effects chain. This device does not create distortion or overdrive on its own. However, it can be used to drive your favorite amp or pedal into singing distorted sustain. Simple, yet effective. Top notch components and circuit design assure that your signal arrives to its destination in a truly pure state.

When you look at the circuit you can see it's basically a modified SHO.





33 comments:

  1. The 2.2m resistor should be connected to the input. Unless I'm missing something.

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  2. Yep. Its not doing much where it is.

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  3. yea. i was moving stuff around to try and shrink it to 10 columns, and give the trimmer enough space to sit flat and forgot i moved the input cap, and needed to move the 2.2M. nice catch guys. also realized both diodes were labeled D2, so fixed that too. should be good to co now. layouts been updated.

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    1. we could delete the F stripe, couldn't we? :D

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    2. Yea you can totally remove the "F" row and move the components and wiring from the bottom up 1 row making it slightly smaller. I personally left the extra row for a reason, space. By moving the bottom up 1 row it puts the trimmer just ever so much closer to the transistor, which I don't like. I prefer to give trimmers a little extra space so nothing gets in its way.

      With that being said you could also remove the last column on the right and move the trimmer and links under the trimmer over to the left 1 column. It's up to you.

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  4. Stupid question i'm sure but what is the trim pot for? Should it be set at anything certain?

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    1. You can just pull it out and run a jumper from source to ground to run it flat out, I prefer the tone of my SHO's flat out. Or you could replace the trimmer with a pot to control the gain externally. Basically the boost knob is really a volume knob and the trimmer is actually the boost/gain knob.

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  6. Works like a charm! Will end up in a box together with Freppos Sonic Reducer, couldn't get enough sustain without whining out of my build. Chers!

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  7. Would a 18v power supply, through a charge pump or so result in more headroom?
    I'm thinking of sticking it as a soloboost into my Rockerverb 50 Mark 1.

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  8. Hiya. I've been lurking on this site for some time, and it's about time I put in my two cents....

    I like this circuit, and it IS a version of a ZVex Super Hard On. That said, I believe that these diodes are not doing their job. They aren't polarity protection and they should in no way affect the sound of the effect. These are protection for the FET in the case of a static shock. You see this on commercial designs because it's cheaper to protect your 25-cent FET with 1-cent diodes rather than have to have the device returned for repair. One diode should be between ground and input, and the other from input to the power rail, though this schematic might be slightly different, that's what these diodes should be doing one way or another. You'll see this in the SHO schematic, and you can use just about any diode to do this ... I've seen zeners, IN400X, and IN4148....whatever is on hand and whatever doesn't affect the tone.

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    1. Like many things in circuits, there's more than one way to skin a cat. Early versions of the SHO used 2 diodes in the configuration you're referring. Later versions of the SHO, many other designs using MOSFETs, and what EQD did with the Black Eye use a diode between the source and gate (cathode to gate) to protect the MOSFET from static shock. I actually traced this pedal myself, and it's the first time I've seen a 1N4001 used to protect a MOSFET. Generally a zener is used and an LED also works for this function (see the Run Off Groove Peppermill). I would assume EQD used 4001s because they already had a ton of them they used for basic polarity protection (which is what the 2nd 4001 is for in this) in all their pedals. So, much like you said, cheaper to use a 1¢ diode you already have on hand then order a whole new diode. But also like you said, the diode you use to protect against static shock shouldn't affect the tone of the circuit.

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  9. Can't get my amp working. Been checking over and over + building it a second time without success. I'm not sure how I put in the 100n capacitor: does it really connect with line 3 and 4 seen from top (can't see any blue dots here)? Thanks for help!

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    1. Hey man. Yes it connects to rows C&D. I'm not sure what blue dots are you talking about? If you're talking about double links there aren't any in this layout. Are you sure you've got the transistor oriented correctly? Did you adjust the trimpot to set the bias?

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    2. Damn - broken cable in the off-board-wiring. Now I've got two brilliantly working amps. Great Job + thanks!

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  10. Very very cool pedal! Thanks Zach.

    Just wondering for the next one:
    The original says 9-18v...would this circuit be able to take a 9v to 18v charge pump in front of it? Will this introduce more clipping, or will the pedal be even louder?

    And what should i do, if i want the boost knob to be 'boost' only. Because now from noon to zero, it's cutting the signal. I would like unity gain to be at zero. :)

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  11. Whether or not you can power this at 18V depends on the voltage ratings of the caps that you used.

    Generally higher voltages result in more headroom and volume, so in a sense, it will probably sound cleaner at 18V, but may have more gain to get more dirt out of your amp.

    To make it so the volume knob doesn't cut the signal, you could use a resistor or trimmer between boost 1 and ground

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    1. Thanks a lot Travis!! This is very good to know!

      I will go nuts on this little circuit with these tweaks :)

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  12. Hi, I'm new to DIY pedals and I have some questions, could someone be so kind to help me?
    Here they are:
    -what are boost 1, boost 2 and boost 3 exactly?
    -where is the output cable?
    -how do I properly connect input and output jacks?
    Sorry if these questions sound stupid, but I'm a beginner...

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    1. Hey man. No worries about the questions, and i think this is a good layout to start off with as a beginner. So let me address them 1 at a time.

      1 - the wires coming off the board are labeled based on where they go. So input is the wire coming from the input, +9V is the wire coming from the power source (DC jack), etc. So the wires labeled boost 1, boost 2, and boost 3 are going to the boost pot, and the number tells you what lug of the pot. So boost 1 goes to lug 1 of the boost pot, boost 2 to lug 2 of the boost pot, boost 3 to lug 3 of the boost pot.

      2 - if you look in the notes below the layout it says boost 2 to output. So you will have a wire from lug 2 of the boost pot that will go to the output.

      3 - to wire up the input and output jacks, as well as the switch is known as offboard wiring. If you look at the top of the site there is a tab labeled "offboard" here you'll see how to wire the jacks, switches, and board together, as well as how to number the pot lugs.

      http://tagboardeffects.blogspot.com/2012/02/offboard-wiring.html?m=1

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    2. Thank you so much, I never thought about offboard wiring. That makes a lot of things clearer now... thank you again!

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  13. I really like this pedal, it works very well. Great design, small and easy. But i have some questions regarding the biasing.

    Because if i bias one for a Strat, i get a strong amount of boost and no clipping at all.
    But as soon as i start biasing for a Les paul. I have to dial the bias waaay back to get no clipping. And now the boost is far from strong.

    And with clipping, i mean that annoying little background noise/rattling in the sound.

    Is there a way around this annoying rattling? Component choice, transistors or maybe some mods?
    (strat pickups around 5.8Kohm and les paul at 7.8Kohm)

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  14. do you think it will be a good idea if I wire this inside the guitar as a buffer and gain control instead of using a clapton mid boost?

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  15. Hi everyone,

    For those who have used the trimpot as an external pot, does it crackle like the SHO ?

    Thanks !

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  17. Hey guys,

    This is my first pedal build, I've done a couple amps. For whatever reason, it sounds like it's gated. I click it on and it takes a second for the signal to come through and it's weaker then the dry signal... as if I had a noise suppressor on max and it just killed the saturation and everything. The only difference is that I couldn't get a 2.2M resistor and only had a 2M.

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    1. I had the BS170 backwards... I'm an idiot. Ahaha

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  18. Wooo! Just finished this, my first working build. Tried two different SHOs that failed, bought some small 3pdt pcb boards, tried this and.. voila, its ALIVE! So excited. Now that I know I can do this I'll probably go crazy building pedals... Thanks so much for this layout and this site!

    Cheers!!

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  19. Just boxed one of these little gems up with a pixel and it works great.

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