The challenge is that good quality NPN germanium transistors like the AC127 have gotten pretty hard to find and are consequently quite expensive--$20 to $30 for a tested pair is about the going rate. If you go this route, be sure to deal with a reputable party; not a good idea buying these on eBay, unless the seller has a ton of positive feedback. Stick with tested pairs--these transistors often have high current leakage and low gain, since many stocks have been "cherry-picked" for the best examples. I'd suggest trying Small Bear Electronics
, a source well known to be trustworthy.
Alternatively, you can modify an ESV Fuzz build to be positive ground so that PNP germs can be used. These are more readily available and about half the price. The downside of a positive ground pedal is that you have to power them either with a 9V battery or dedicate a "wall wart" to them. If "daisy-chained" with a negative ground pedal (the vast majority of effects pedals are this type) on the same power supply, a power short to ground is created, and neither pedal will work. The build modifications are pretty simple to make the ESV Fuzz positive ground--you have to modify the wiring to be like the positive ground ESV 2-Knob Bender
, and the 22uf electrolytic cap and LED need to be mounted with the opposite polarity.
One more option of note if you decide to go with a positive ground configuration: our pal Brian over at Madbean Pedals
sells a nifty little PCB called the "Road Rage" that will convert normal +9V voltage supply to (among other things!) -9V, which can then be used to power a positive ground ESV Fuzz without all the wiring changes. This makes a positive ground pedal power-compatible with negative ground pedals, so no dedicated PS is required. I just finished an ESV Fuzz kit night before last built exactly this way, and it works like a charm. Used a pair of tested & matched PNP germs that I bought from another forum member here, and the pedal sounds fantastic. I have a wiring diagram for the ESV Fuzz/Road Rage combo if you (or anyone else) needs it.