The Acapulco Gold by Earthquaker Devices—relative to its low parts count, this pedal is an absolute monster. A loud monster. I’ve built it quite a few times, and have learned a lot from it, as it is an interesting circuit. Two power amps in series, each pretty much straight out of the LM386 data sheet, with some frequency and gain manipulation on either side. One knob for loudness. Cleans up nicely with your guitar’s volume knob. And it works great for bass. There are plenty of layouts readily available on the web—I myself have had good experiences with those up on the Tagboard and EffectsLayouts blogs, so I’d recommend you go check and those out if you’re into building the original version of this circuit.
However, know that the AG is really moddable, which is exactly what Alec over at Mask Audio Electronics has done with his Glass Jaw Fuzz. I first encountered the layout and schematic over at the EffectsLayouts blog. It’s an AG preceded by a dual buffer—one going to the AG, and the other to a clean channel which is blended back in with the dirty AG signal at the end of the circuit. In between the two LM386 power amps you’ve got a Baxandall tone stack, giving you separate treble (Glass) and bass (Thud) tone controls. I’ve made two layouts—one for the fully featured circuit, and the second is a simplified one-knobber with internal trimmers.
The first layout is for 1590B-style enclosures with the four external knobs:
The second layout is on perf board, fits in a 1590A-style enclosure, and includes a single external knob for the Clean control, as well as three internal trimmers for Loud, Glass, and Thud. But theoretically, you could easily modify the circuit so that any one of these controls can be switched out for an internal trimmer or external pot. I haven’t tried it myself, but you’re more than welcome to. Anyway, here’s the perf layout:
Here are a few pics from my own builds for both of these: