The ' Little Gem ' - Mini Amplifier / Guitar Amp -

This is a mini guitar amp based on the Little Gem amplifier, found at runoffgroove.com.  The unit produces only 1/2 a watt, if you want to produce a full watt to drive a 12" speaker, then I suggest building the Little Gem MKII (PDF layout attached).   The amp sounds pretty dang good for what it is, and clips can be found at the site I just mentioned above.

Listen to it here

What I want to show you (conceptually) is how to use one of these as a portable mini guitar or practice amp that already has some good sounding distortion.  

My last instructable (attempted) to do this, but I think the sound quality of that amplifier doesn't compare to this one.   The distortion tone is a huge improvement,  and the same concepts (switchable tone capacitors) can all be applied to this as well. 

You can build this with or without a Volume pot, I chose not to since it doesn't get extremely loud to my ear after playing through a Fender SS tube amp (last pic).  So I mean this isn't going to 'take over' as your main rig, and you won't be able to play to 500 people - but it's great for taking your electric guitar camping. Seriously. Try it.  It's fun, be a guitar geek.  Blaaaack Beauuuuuty is my main axe ; I hope you like ooogling her as well. 

Step 1:

Comments

[jajer]

Would it be possible to embed this amp into the guitar itself?

[Bulantuy]

i build this in a past few days but my amp wont work properly i mean it sound but in very weak and distorted sound i don't put 10 uf cap in pin 1 and 8 in my country lm386 it's don't look lm386 in radioshack i live in phil

can any one help me to figure it out the problem

[iamtoats]

That sounds pretty good.
You should try running it into your Fender's speaker. (not the input, the speaker leads.....)

[capth00k]

Might try that, but with an Little Gem MKII (1 watt) , since the Celestion Vintage 30 that's in there is 60 watts I think ; and I don't see it making a lot of noise... well, not what I am used to anyway. For a practice amp with a smaller sized 4ohm speaker, this rocks. From what I understand you can run 16 ohm 2 x 12's at just above conversation levels with this Little Gem 1/2 watt. Tried running a 4ohm , 8" subwoofer speaker (35 watts I think?) from another project and it sounded O.K., but that one sounds a hell of a lot better being driven with a 30 watt head.

[bennay]

HiYa capth00k, sorry for the newb question but I'm finding it hard to find the correct "gain" POT, can i just use any 5k linear pot? ebay just confused the hell out of me with ever-so-slightly different versions :(

[croberts17]

hey friend, i'm trying to do this same thing with another couple of op amps i found, 4558 chips, i have attached an image of the circuit i drew, i haven't tried it out but wanted to know if you have any advice for my circuitry :) i'm not sure what these chips can actually handle but i would love to try this. :) i've got 2 power supplys and 4 chips lol

[emihackr97]

how can I add a Headphones jack????

[smash10101]

try putting it where the speaker would go, or add on on/on switch where one goes to the speaker & one to the headphone port

[login721]

Hello , can i use a 470uF instead of 220uF capacitor at output ??

[LkArio]

I connected this to a single 4 ohm speaker, it sounded better, pretty much. Better than the two 4 ohm speakers on series that I had before...

[mmeeker]

you guys should all check out the tube reamer effect at http://runoffgroove.com/tubereamer.html

[mmeeker]

Man i had to unsolder my board once but i finally got haha i couldn't figure out where you were going because you didn't list a - on the layout but i got it now it sounds great

[capth00k]

Ohhhhh, your ground connections. Gotchya.

[mmeeker]

oh i'm sorry man i don't know much about this kinda stuff at all this was my first project but i thought the LM386 had a V+ and V- but it only has a V+ lol like i said my bad. Now that i know how to do this it has helped me with other projects i've been working on like a LM3886 Amp and a couple of pedals.

[capth00k]

Right on man. What did I forget to list ?

[LkArio]

Hehe, I did it. It was a lot louder than I expected for the LM386N-1 version, and it seemed to drain 1V off my battery after about 20 minutes. The distortion is awesome. Nice instructable.

[capth00k]

Right on man. Enjoy. I like this Little Gem design for the same reason - distortion sounds great! Just enough, and not too much :)

[LkArio]

Nice instructable!
Would it be possible to have good distortion with the LM386-3 or LM386-4 version of this chip?

[black_dot]

hi , im new to electronic so i have no idea how to do this , how do i connect the components together if im not using the volume control

[reginaron]

Hi. Mabye your'e the right person to ask.

I have a cheap AC/DC, 2 speaker set ,that can be used either trough a PC, or a CD player. Amplified system.
This ( main speaker unit), has a 1/8","mic" input on the front and a 2nd on the back.
So I attached an 1/4f -1/8 m,adapter from my guitar,and cord to the " mic ",in the front,and back. ZERO sound.
Power / Vol all good. Is a preamp neccessary?
Thanx for any suggestions.

RJ

[emmett1989]

i cant find 0.047uF in my nearest store? can i change this value?

can i use 10k pot for the volume pot and gain pot?

[warfighter]

what are the values of the resistors. pls use like nF or pF or uF
because im dutch and i cant find by these names

[capth00k]

10 ohm

[capth00k]

The Only resistor in the Little Gem layout is :

10 OHM - (brown, black, black, gold)

not to be confused with a 10K

hope this helps.

[capth00k]

Capacitor Values:

0.01 uF
0.047 uF
220 uF
100 uF

[green_emi]

Noob question:
are all the capacitor values on the MK2 diagram in uF aswell? its a bit confusing when some of them have units but not others

[emmett1989]

Hi capth00k, can use this project as pre-amp?

[capth00k]

Sure, but I would (personally) build something like an Alembic Stratoblaster for that. A really simple tag board layout is attached of the Alembic. Great for screaming guitar tones or mild overdriving of amp (depends on how set)

[PieMaster777]

Your Black Beauty is Beautiful, and the amp is nice too!

[capth00k]

Thanks mate, have to gloat a tad and show off the gear for all us gear slutZ. I still can't believe they're all mine .... ! lots of hard work !!

Peace, Capt :)

[da animal freak]

great instructable. what was that little tune you played on the amp? i really like it! if you have the tabs please post it on here, thanks!

[capth00k]

The clip wasn't me, it was actually from the makers of the Little Gem MK II circuit which I used to assemble the portable amp.

[da animal freak]

oh nevermind then, but still thank fo the instructions!

[Schober]

I'm building this mini amp on a self etched circuit baoard and was wondering how you went about bypassing the Volume pot. and if you could show me how to do so on the circuit diagram found in the PDF. I was also wondering how the amp sounds without the pot.

[capth00k]

I decided not to run a volume pot because it doesn't get too loud anyway, and I just turn the gain down. You can run the Little Gem PCB output straight into the + of a speaker - - instead of soldered to the pot, then off the pot and to your speaker.