navigationGo.pngQuick Navigation
allprojects32.pngAll projects

favoriteStar32.pngTop projects
Alan numitron clock
Clapclap 2313/1386
SNES Pi Webserver
USB Volume/USB toys
Smokey amp
Laser cutter
ardReveil v3
SNES Arcade cabinet
Game boy projects
Home Presence Detector


navigationMail.pngContact me

3flags.pngWho's Alan?

Rand Nerd Tut
Datasheet Lib
Reddit Elec
Carnet du maker (fr)
ATmel blog (defunct)

Smokey amp vII

kalshagar - Smokey amp vII

Version 2 Info

Based around a LM386 amplifier (in my case a JRC 386), the idea was to make it for a guitarist colleague, and also for myself maybe.
... continued from Smokey amp vI
20101103: worked on the amp tonight on a breadboard. Well, I understood a few more points, by testing and looking at other schemas of smokey-amp like (in the link section):
  • The final cap between output and speaker controls the tone. By changing the value your amp will sound different.
  • Some people use a pull-down resistor (1 M ohm) between input%20 and ground ... don't really hear a difference
  • Using a tiny ferrite on the input doesn't improve the sound much, but if not present there is no sound at all or extremely hashed sound on the breadboard version... wtf?
  • A pot on the gain is not necessary, really, it's like the volumn on the guitar itself
  • A 10 ohm and cap to ground the output pin makes no sound any more on the speaker (but some people have that)
  • On the breadboard version, no much background noise : why ?
  • Sound is really distorted, specially the low tone strings. Playing hard rock/metal is cool with it, playing a ballad or folk is so-so (bass end up so loud and sustained that if completely hides the high tone strings). "Nothing else matters" doesn't sound so good.
  • The "small cap" (22pF) between the input%20 and input- pin is not a killer ... but on the version 1 (not breadboard) it doesn't have that much of bad impact if not really positive. I think I hear less the radio since I put the little cap which can understand since it must eat-away small variations, aka. that faint radio in the back.
20101104: again spent some time playing with the breadboard version, got a few more interresting conclusion
  • VERY IMPORTANT : a big fat cap between the power rails make the sound much better. Indeed, the amp must generate a lot of variations on the power supply and it distorts the sound and make it sensitive to the ambient magnetic noise.
  • IMPORTANT : add a pot for the gain, or at least a little resistor since at maximum level the noise is too low. But just lower it a little, and the sound becomes much much better.
  • Adding a cap between guitar input and input%20 (like a 47uF) make the sound a bit cleaner but I would say with a little less "detail" (sorry, I'm not good at music neither). However sound is more clean. Maybe there is a tradeoff here?
  • A cap between output and ground is not necessary (no big difference). And if you put a resistor, mind that a single 10ohm baby will get burning in a few seconds... make it serial with a cap if you want. Maybe it worth being tried?
Anyway, thanks to all this, I'll make a version 2 this weekend. Hope result will be nice ^^
20101108: made version 2 on Friday evening. No cap on the input, but a ferrite. Is it a crime or something great (or just useless) ? Dunno. Put also a BIG FAT cap (470 uF) on the power rail and that's a killer : barely no more noise and sound is much more clean. Also important. this one has a gain control pot (10k, too big but I have nothing smaller currently) which is very good : full power you still have noise, but if you just lower it a bit, then bye bye noise and enjoy a clear sound that is plenty sufficient for playing at home on the sofa. Schema coming soon...
20101110: found some guy's comment on I copy the guy's comment on a separate page to keep it. Thanks for sharing, that will be most useful I guess.
20101118: well I tried many tricks, tried to implement many alternate Smokey amp like the Smokey Tone Amp of BeavisAudio, variations found on internet ... same : I've got lots of noise. A pot on the gain and a big cap between power rails make things better but no miracle here, I've still got lots of distortion and a background noise. Impossible to get a clear and clean noise.
20101128: it's not because sound is not perfect (hum hum ... far from it in fact) that I should not use it and case it into something. As you can see on the right hand picture, I cased it in a metal "hot lemon tea" can. The plug is in the top cap, and the speaker at the bottom. I tried to fix the speaker with nut and bolts, but to fix the nut to the speaker I soldered it but it didn't stay in place once a little force is applied. Maybe with an arc soldering tool I could, but nothing like that at home, so I will replace it with steel wires, should do the trick.
Only interresting stuff is that now - from power goes to the middle section of the 6.3 mm plug and goes back from the top (not the tip, the other side). Benefit ? Well, no need for a switch, if nothing is plugged in, the circuit is open and battery unused. Got the idea by seing a real SmokeyAmp once.
... continues on Smokey amp vIII


Version 2, with gain pot and tone control (useless)
Version 2, case into a metal can of hot lemon drink.


All content on this site is shared under the MIT licence (do what u want, don't sue me, hat tip appreciated) ~ Formerly known as (AlanFromJapan [2009 - 2018])