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.





13 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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  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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