Earthquaker Devices - Acapulco Gold [schematic]

[toxsyn]

Never mind. He sold the pedal on eBay.

[captain_tango]

Put it on breadboard. The circuit works, but we knew that already. Whether or not it's the same, I can't tell. I only ran it through a Micro CUBE with a cheap headset, but from what I could tell, it had copious amounts of volume, but not a very nice tone (At least going from what we know and just adding different values to the mystery caps). I guess we need more pictures and better analysis and also I should be taking the breadboard down to the studio and feed it through a proper amp. But one thing's for sure and that's that I'll be doing a lot more with LM386 after this! Really cool device! I ended up with one op-amp on my board, 470n in and out of the chip and 47u across pins 1 and 8 and I can't wait to try it on a proper amp! 4 components for amazing distortion?!

[Hexjibber]

Put it on breadboard. The circuit works, but we knew that already. Whether or not it's the same, I can't tell. I only ran it through a Micro CUBE with a cheap headset, but from what I could tell, it had copious amounts of volume, but not a very nice tone (At least going from what we know and just adding different values to the mystery caps). I guess we need more pictures and better analysis and also I should be taking the breadboard down to the studio and feed it through a proper amp. But one thing's for sure and that's that I'll be doing a lot more with LM386 after this! Really cool device! I ended up with one op-amp on my board, 470n in and out of the chip and 47u across pins 1 and 8 and I can't wait to try it on a proper amp! 4 components for amazing distortion?!

Cool thanks for giving it a go and sharing your findings, I'm guessing the 'magic' in terms of the tone is all in those cap values presuming I've drawn out the schem correctly! Need to get myself a breadboard set up and try this one out really! Did you get a distortion sound but just not a very nice one or was it a big ol' clean boost?

[captain_tango]

Distortion. Absolutely. Powered it up in front of a real amp today. It sounds misbiased and farty with a crazy sizzle that seems to lessen a bit when you filter the power. It's just not really nice sounding. Looking forward to trying it with the proper caps if that ever surfaces!

[captain_tango]

Sorry just came to think: does it matter at all which kind of 386 I'm using? Mine is the LM386L, but I see there's an "N" available too and earthquaker are using the JRC386D... Am I on the wrong chipmobile here?

[Hexjibber]

Sorry just came to think: does it matter at all which kind of 386 I'm using? Mine is the LM386L, but I see there's an "N" available too and earthquaker are using the JRC386D... Am I on the wrong chipmobile here?

Possibly relevant;

http://www.diystompboxes.com/smfforum/index.php?topic=94327.0

[captain_tango]

Alright! Maybe I'll try the D, then.

[toxsyn]

I played the original for about an hour. It's not a very versatile sound. It's great for getting a Red Fang tone. you can use it as a preamp and it sounds a little better that way. Definitely fuzzy and farty. The more you turn up that huge dial the worse the sound gets.

[captain_tango]

Tried it with LM386 N-1 and JRC386D now. Both sound quite a bit better. Less flatulent. Ditching the 10uF from pin 1 to 8 also seems to cool down on the craziness, but I still find that using just one chip with caps in and out sounds a whole lot nicer. Softer, surely, but better. So it wasn't for nothing. I think I will cook something nice out of the this chip, but I really look forward to seeing the correct cap values in the future if someone stumbles across them! Try using one JRC386D and go with 100nF from input jack to pin 3, tie pins 2 and 4 to ground and go 100nF from pin 5 to output and strap a monolithic 1uF across pins 1 and 8 and you have a fantastic little Keith Richards Style grind with only four components! Amazing

[Hexjibber]

Tried it with LM386 N-1 and JRC386D now. Both sound quite a bit better. Less flatulent. Ditching the 10uF from pin 1 to 8 also seems to cool down on the craziness, but I still find that using just one chip with caps in and out sounds a whole lot nicer. Softer, surely, but better. So it wasn't for nothing. I think I will cook something nice out of the this chip, but I really look forward to seeing the correct cap values in the future if someone stumbles across them! Try using one JRC386D and go with 100nF from input jack to pin 3, tie pins 2 and 4 to ground and go 100nF from pin 5 to output and strap a monolithic 1uF across pins 1 and 8 and you have a fantastic little Keith Richards Style grind with only four components! Amazing

Thanks for sharing your findings man! I have as yet not got a breadboard so has been really interesting reading your experience with it!

[danndubblewe]

Long time lurker, few time poster. I picked one of these up and just sold it but opened it up and got shots and values, I'll post them later today!

[bigbonedstacks]

Long time lurker, few time poster. I picked one of these up and just sold it but opened it up and got shots and values, I'll post them later today!

[modman]

BOOP

Hope this helps out in some way! I am not good at making layouts/ am a novice at best following schematics but these are the values for certain. The "472" code on the one poly cap was really hard to read, but that's what it was. Should be good fodder for mods? That and I can't wait to build one for my personal collection.



The image at this time seems to be taking forever to upload to my cheap free server, so I'm attaching it as well.

[modman]

that 1uf to the left should've also been 50v

[modman]

Amazing! Thanks a lot Dan!

Here's an updated schem based on Dan's pics;



Still not 100% sure I have the layout correct, specifically the two caps and resistor between the ICs but we at least have the values, if anyone can verify that would be great!

Cheers

[Nocentelli]

I wonder if the 4n7 is connected to ground to roll off some treble before being amplified again

[danndubblewe]

I'm not shipping it until tomorrow, if you guys think of something else you need me to do just ask - you may have to walk me through it but I'll do whatever I can.

Also forgot to mention the pot is A100K, not linear as the PCB would have you think.

[captain_tango]

I'm not shipping it until tomorrow, if you guys think of something else you need me to do just ask - you may have to walk me through it but I'll do whatever I can.

Also forgot to mention the pot is A100K, not linear as the PCB would have you think.

Thanks! Can you possibly take good photos of the traces on the PCB, both sides? That would really help! I'd personally like to know where both ends of that 4n7 are going! Also the 68K. It makes no sense to use a 1uF then a 68K, then a 4n7 between the two stages! I'm thinking the 68K should be at the input. Would make sense as it's supposed to mimic an amp. Amps often have the 68K at the input.

I would guess that 4n7 has something to do with rolling off highs, as previously stated. Also, are we sure the gain cap between 1 and 8 is indeed 10?

So yes, a thorough trace job would be just amazing, but thanks for all your help so far!

[Hexjibber]

Also forgot to mention the pot is A100K, not linear as the PCB would have you think.

I guess the pot taper depends on location, in this case I'm guessing that it's linear as the code in the US is B for that, the pot itself could be the Euro designation of linear though, which is A. Would seem odd to mark the pot as B and then use an A?

[Nocentelli]

Tried it out, and swapped all the visible parts into every sensible arrangement possible. Seems to me the 4n7 should go to ground off pin 3 on the second 386, and the 68k should link the 1u from the output of the first 386 direct to the input of the second. You get a slightly different sound if the 10u is from pin 1->8 on the first or second 386, both are usable.

One thing that seems significant to me, it that even with a 100kA pot, the output is massive. As with most 386 based dirt, the decay is not very smooth, and there is a noticeable fall off as the guitar signal decays below the "headroom saturation level" of the circuit. I notice in this clip, the volume knob is very low (like I had mine so i didn't go deaf):


Link


Whereas in this proguitar shop demo, he has the level knob really high: I am guessing this is massively driving a nice tube amp, and contributes to the smoothing out of the slightly yucky decay (even though, if you watch carefully, he never allows the note to fade out to silence)


Link