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Friday, December 22, 2017

EarthQuaker Devices Erupter

Merry Fuzz Friday, everyone! Here's EQD's latest fuzz offering, the Erupter. Essentially it's a JFET buffer into a pickup sim (the transformer) into a Fuzz Face-esque circuit. The Bias control controls the amount of voltage going to Q3 and is a center detent pot (though a regular B10k pot will work just fine). This one might benefit by adding a volume control to the output. Should fit in a 1590B just fine. The 2N497 transistor might be hard to source, but other low gain transistors should work. Schematic can be found here.


28 comments:

  1. Transformer arrives today from Mouser. I'll try to verify over the weekend.

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  2. if i want a volume what pot should i use ? is there any good remplacement for 2n497 ?

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    Replies
    1. Probably an A100k or maybe an A500k since it's so similar to a Fuzz Face.

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  3. There is one original version of the Erupter that uses a 100k trimpot as an output volume control.

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  4. Any substitute for the pf5102?

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  5. Does it have to be that transformer or can a similar one be used?

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    Replies
    1. A similar one could probably be used, just compare datasheets.

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  6. What kind of part is represented by the blue box with the 5K on it?

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  7. I just finished the circuit and tested it without success. Any tips on debugging or common mistakes with this board?

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  8. Any suggestions for the 2n497? they're $22 at mouser, yikes!

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    Replies
    1. That section of the circuit is essentially a fuzz face, so anything with lower-mid hfe gain will probably be fine.

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  9. good morning, any suggestion to replace 2n497, I live in Brazil and here is so difficult some transistor...Please help me

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    Replies
    1. Low-medium gain NPN silicons will work just fine. 2N2222A, 2N2369, 2N5550, etc.

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    2. For Q1 can i use an 2n7000? I cant find the j201 and 2n5457 in my town :( any other replace??

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    3. The 2N7000 is a MOSFET and isn't a direct replacement for the J201 or 2N5457. You'll need some sort of N-channel JFET. Comparing datasheets of what you can get to the J201 is probably your best bet.

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  10. Ok thanks... one last question, what kind of think do the trimmer? I need to regulate or something like that,?

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    Replies
    1. The trimmer is there to set the minimum amount of voltage supplied to Q3 by the Bias pot. It's something you'll need to adjust by ear. I'd start by setting it half way and making sure the the circuit works at all rotations of the Bias pot. Then adjust as necessary

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  11. Hello,
    Is there any gerber file and pcb specifications for this pedal?

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  12. Built it but getting really bad oscillation at any bias below 6v - any ideas? Cheers!

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  13. IM also getting oscilation unless my bias pot is over 85% clockwise. Woud this be due to the transistors? i used pn2222 and have checked the pinout. I also used a pf5102 for the jfet

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  14. The transistor is 2n4970, not the 497...in case you're having trouble finding them/cheap

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