SOLVED Aztek Sunn // Acapulco Gold too much gain?

Fama

Fama

Well-known member
Hello!

I built the Moonn Aztek Sunn which is an Acapulco Gold with apparently the Sunn Model T EQ stack (well, you can build it with one knob, two knobs or 5 knobs). Here's the build doc with the schematics https://www.dropbox.com/s/pm2pr5tf7ezz8uh/Aztek Sunn Doc V2.pdf?dl=0

My issue is that it seems that the circuit has too much gain. It gets blown out easily, and although I can coax some usable sounds from it in certain pot configurations, if I roll my guitar volume down a bunch it seems to act like it "should". I think it also oscillates when the volume and gain are full and treble is pretty high up? Or at least there is a whistling sound that changes frequency with the guitar volume or treble knob. I also noticed that I pick up some foreign Asian radio if I have my guitar volume set to 0 but I'm not grounding it (not touching the strings).

I can't show a pic of the solder side (well, I could, but it would be useless since the pots are in the way).

I used LM386N-1's since that's the only one Tayda sells. Could this be the issue? I only just read that there are different variations. There's also a small chance that one of the resistors is bridged with the ground wire - but I'm fairly sure that's not the issue, and I've been wary of reflowing it because it's right in between of two different capacitors and I don't want to melt those.

I also bent the legs of one of the LM386's trying to get it into the socket, but I think I got them straightened quite well and they are securely in the sockets now.

Here's a sound example with clean guitar, then the Aztek Sunn on two different settings, and finally some radio and background buzz because I thought it was funny.

https://soundcloud.com/user-913671490%2Faztek-sunn-example%2Fs-LdwlwecynfG
 

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I noticed another weird behavior - with gain and volume at full, if I play and stop playing, the sound cuts out for a bit after I stop before it resumes. So sort of gating I guess? But it doesn't gate when I'm not playing like a gating fuzz would, just for a split second when I mute a note for example - the sound then resumes while nothing is playing.
 
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PJS said:
I am not keen on the soldering of the volume pot or the footswitch
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I think I'll re-do the volume pot - I'm a bit wary of soldering a footswitch full on (especially with round holes), because I've soldered one on the wrong side before and had to re-do it which is a huge pain (plus I only have thin solder right now), but I can also fix that up if you think it might help?
 
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The volume looks more problematic than the switch. Personally I don't use boards for footswitches because they are more hassle than they are worth IMO. The switch can be easily checked for continuity to make sure it is connected properly with the solder that is there.
 
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PJS said:
The volume looks more problematic than the switch. Personally I don't use boards for footswitches because they are more hassle than they are worth IMO. The switch can be easily checked for continuity to make sure it is connected properly with the solder that is there.
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I re-did the volume and gain pots (plus the ground wire for power jack), they're good now but it didn't help.

Edit: Also touched up the mids pot and switched to new LM386's but no dice.
 
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FWIW I used LM386N's from Tayda (I think they're LM386N-1), which didn't seem faulty, but googling more about this issue it's a common thing people run into with this build and exactly LM386N-1's. Apparently JRC386BD's would be better, but those seem to have been discontinued? Alternatively LM386N-4's have worked better too.

I happened to also have LM386L's from Tayda, and switching both IC's to those fixed my issues. No oscillation, no dropout/limiting effect (which is the "after you play a note and mute it, the sound cuts out for a moment before coming back" I mentioned), and it overall just sounds much better. So for anyone else who might run into the same issue with any Acapulco gold builds, avoid LM386N-1's.

I'm still not 100% happy with it since I only really liked the sound with the bass pot turned up full and treble at almost zero (mids works nicely though), but then again I was testing just with a low output strat, so I'll try with other guitars - it could be that the controls work much better there. I also have to desolder the treble and bass pots anyway since I'm hoping I can make them fit in the enclosure the other way around since I made a mistake in the print files, so I'll try to wire them up - I could do some mods there too to change the ranges if needed.
 
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Fama said:
FWIW I used LM386N's from Tayda (I think they're LM386N-1), which didn't seem faulty, but googling more about this issue it's a common thing people run into with this build and exactly LM386N-1's. Apparently JRC386BD's would be better, but those seem to have been discontinued? Alternatively LM386N-4's have worked better too.

I happened to also have LM386L's from Tayda, and switching both IC's to those fixed my issues. No oscillation, no dropout/limiting effect (which is the "after you play a note and mute it, the sound cuts out for a moment before coming back" I mentioned), and it overall just sounds much better. So for anyone else who might run into the same issue with any Acapulco gold builds, avoid LM386N-1's.

I'm still not 100% happy with it since I only really liked the sound with the bass pot turned up full and treble at almost zero (mids works nicely though), but then again I was testing just with a low output strat, so I'll try with other guitars - it could be that the controls work much better there. I also have to desolder the treble and bass pots anyway since I'm hoping I can make them fit in the enclosure the other way around since I made a mistake in the print files, so I'll try to wire them up - I could do some mods there too to change the ranges if needed.
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I can’t speak for Moonn (I’m actually looking at making a first purchase with them shortly, the Space Is Fun pcb). I did just build a couple of the Acapulco Tone’s from PCBMania and they’re pretty awesome. It’s a four knob version with EQ and a Clean Blend. I will say, however, that you have to be careful with PCBMania though. Their pcbs don’t always perform the way they should, or at all in some cases. I can confirm the Acapulco Tone does and it’s pretty sweet. As mentioned prior, I’ve used the LM386n3’s and JRC386D’s with no issue. Not so much with the LM386n1’s. Hope that helps!

pcbguitarmania.com

Acapulco Tone - PCB Guitar Mania

Inspired by EQD Acapulco Gold + Clean blend & Baxandall tone stack.
pcbguitarmania.com pcbguitarmania.com
 
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I built the full tonestack version of this with no issues using LM386-1 ICs.

One thing I'd like to add is that this circuit might work better with a 500K volume pot as amp style tonestacks like to go into a larger load than 100K usually. Else it will be pretty bright and lacking bass unless you crank it.
 
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jesuscrisp said:
I built the full tonestack version of this with no issues using LM386-1 ICs.

One thing I'd like to add is that this circuit might work better with a 500K volume pot as amp style tonestacks like to go into a larger load than 100K usually. Else it will be pretty bright and lacking bass unless you crank it.
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Thanks for the info, I did find that it was really bright and lacking bass unless I cranked the bass. It did sound good with (almost) cranked bass, but I'll try it.
 
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