Half-Hour Hacks - EHX Screaming Bird

IMG_20140809_164748_976 The EHX Nano Screaming Bird is a reissue of a 70s EHX design. Personally, I've not been a fan of mine - it's far too screechy and has dumptrucks full of high-end and not much else on my setup. I found myself kicking about the workshop with a little time to spare, so I decided to do a quick mod I'd read about online. This allows an easy conversion to LPB-1 spec, turning the treble-boosting screaming bird into a more useful flat booster.

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Like most current EHX pedals, it's true bypass, solidly built, and a minor pain to wriggle out of its enclosure. It's also using a fair few SMD components. However, most interesting is the PCB. What's up with those unpopulated pads? IMG_20140809_165457_099

This board is labelled as the "EC-D55 Rev. A". Near the potentiometer, it can be seen there's another set of 3 pads, labelled for a 10k pot as opposed to the 100k installed here. This is noted for the "EC-D56" design, the 100k being used for our "EC-D55" and also the "EC-D12". A quick Google wasn't conclusive, but I'd put my money on EHX using the same board and layout for not only the Screaming Bird, but the previously mentioned LPB-1 (I'm betting EC-D12), and the bass-boosting Mole (I'm betting EC-D56).  On the opposite side of the board, we noted the unpopulated pads, labelled with different model numbers for the slight differences between different circuits. The EC-D55 Screaming Bird and the EC-D12 seem to share the most likeness.

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To push the Screaming Bird closer to LBP-1 spec, simply change the two 2.2n caps (C12 and C13) out for a couple of 0.15uF caps.  I couldn't find two 0.15uFs, and in the spirit of "getting it done", chucked in a 0.15 and an 0.1. The great thing about audio electronics is that this is generally just fine. Worst case, I'll swap it next time. There are also a couple of resistor values different between the LPB-1 and Screaming Bird but they're pretty minor changes - we're just trying to get closer, not exact. It'd be trivial to swap them if you're feeling picky.IMG_20140809_174514_763

Put it all back together and whack a nicer knob on it. I never really liked the basic EHX round one and it was jammed on way too tight anyway. All in all this was a fun little hack that only took 20 minutes, and has given me a pedal I'm much more interested in using! Try it out yourself, or let us know about your own mods in the comments!