Acapulco Gold & Glass Jaw Fuzz

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:

Glass Jaw vero layout designed for minimal off-board wiring

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:

Glass Jaw perf layout designed for 1590A (mini) enclosure with internal controls

Here are a few pics from my own builds for both of these:

1 thought on “Acapulco Gold & Glass Jaw Fuzz”

  • Thanks for sharing! I built this using the 1590B layout. A few things to note if anyone is interested in building it. Also, Daniel was very helpful in clearing these things up.

    1. The polarity protection diode needs reversed. It is shown in series with the 9V connection, so it must flow from positive to negative. I used a 1N5817 because the forward voltage drop is low, so I didn’t lose very much voltage putting it in series. You could also put a 1N4001 from 9V to GND (anode at GND, cathode at 9V). This is how the 1590A layout is wired. I generally prefer the diode in series method since it offers better protection.

    2. Lug 2 of the CLEAN pot must not connect to the board. Just solder the output wire to the lug.

    3. Pin2 and Pin3 of each LM386 on this layout are reversed from the typical LM386 application, and all other Acapulco Gold and Glass Jaw schematics/layouts online. I asked Daniel about this and he said he had a batch of LM386s where these pins were reversed (manufacturing error), so he made his layouts to accommodate this. I reworked the layout for pins 2 and 3 to be wired correctly, and my build works fine, so apparently my batch of LM386s are not reversed.

    4. Input and output pull down resistors would be a good idea to make sure there is no pop when switching (1Mohm should be fine).

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