DIY Mini-Amp Goes to Eleven

On the day mini-amps were invented, electric guitar players the world over rejoiced.  No longer would they be house-bound when jamming out on their favourite guitar. It is a doubly wondrous day indeed when an electric guitar-inclined maker realizes they can make their own.

[Frank Olson Music] took apart an old pair of headphones and salvaged the speakers — perhaps intending to replicate a vintage sound — and set them aside. Relying on the incisive application of an X-Acto knife, [Olson] made swift work cutting some basswood planks into pieces of the amp before gluing them together — sizing it to be only just bigger than the speakers. A tie was also shown no mercy and used as a dapper grille screen. Both the head and speaker cabinets were sanded and stained for a matching finish.

The speakers are wired to a simple aux jack and connect to an LM386 low-voltage amp circuit which [Olson] assembled and mounted into the header. In spite of our earlier hype, [Olson] seems to be using an external power supply for this mini-amp; but before you count that as a mark against this build, the music you hear him playing in the build video came from the amp. Pair that with this mini-not-quite-a-Tesla-coil, and you’re ready to jam.

25 thoughts on “DIY Mini-Amp Goes to Eleven

      1. It is loooong in the tooth – over 30 years old at least. There’s a myriad of modern alternatives which offer a better frequency response for a similar price/component count.

        1. What do you think is wrong with the frequency response of the LM386? And how does being old imply it’s no longer suitable? PS you can buy new ones. You can also buy 555 timers and 741 op amps… because they are plenty good enough.

          Please don’t try to convince the man it’s necessary to put mags on a Smart Car, so to speak. The point of diminishing returns has already been reached at the design/capability of the speakers.

          The LM386 is just fine. If you wanted to extend battery power and have a bridged output, you could try a small class-D amp IC. But it wouldn’t sound any better in this application.

        2. The thing with the LM386 is you get a real nice dirty sound when you put a pot on 1 and 8. I haven’t been able to emulate that break up on any other type of chip. The LM386 in my opinion comes the closest I’ve heard to sounding like vacuum tube break up

        3. Go to a hamfest. You will find people asking large boxes full of components of that vintage for almost nothing. Sometimes it really is for nothing, they give it away free.

          Pair that up with the fact that there are so many designs using such stuff on the internet and in old magazines… You can keep building almost forever, almost for free.

          Also, among the old parts there are common favorites. Stock up on lm386, 555 and ne502s… now you can find a design to build almost anything without waiting for shipment. With modern components there are so many to choose from. Which ones do you stock up on?

  1. My high school drafting teacher would not have been pleased with his use of a scale as a straightedge.

    Sounds surprisingly good if it’s really the guitar straight into an LM386 circuit and out those little speakers.

    Probably good money to be made on exact miniature Fender Twin, Marshall, or other classic amps, until you get sued.

    1. Not trying to be that guy but you described a thing I use all of the time for audio gear testing. I use a Marshall MS-1 micro guitar amplifier. It is a great little box. I personally like it for testing because I never have to worry about being connected to the wall, losing hundreds of dollars if it gets blown, and it works fine with guitar or line levels. Even has an output to run into the big boys. Looks like they have had a few releases since mine (yay thrift store). Then again, the article’s circuit is even cheaper to build and does a decent job :) Best to ya
      https://www.amazon.com/Marshall-MS2-Micro-Guitar-Amplifier/dp/B000BVS7WQ

    2. What actual problem do you consider to result from using a scale as a straightedge? Those scale rulers make excellent straightedges IMO because the shape keeps them rigid, unlike flat rulers.

      1. Use the scale for measuring and making marks, but don’t drag anything (i.e. pencil, and certainly not a knife) along the edge to erode the edge and/or markings.
        Back in the manual drafting days that was probably a more important rule than it is now, but old habits die hard. Back then, drawing along the edge of a scale was like pounding in a nail with a screwdriver handle. It works, but not a good idea if you want your tools to last forever.

        1. Interesting. But did you ever see a scale worn down by a pencil? How long would that really take? Seems like a perfectly serviceable tool life, unless the scale is made out of an incredibly soft material.

          1. no… I’ve never seen one worn down and don’t expect to – especially since there’s so little manual drafting anymore.
            ut that’s what was pounded into me back then. A little bit of googling seems to find at least someone that agrees with that mentality:

            From http://www.tpub.com/engbas/3-11.htm
            “Note that your pencil touches the scale only for the purpose of marking a point on the paper. Never use a scale as a straightedge for drawing lines. A typical office ruler has a metal edge; it is a scale and straightedge combined. But a draftsman’s measuring scale is for measuring only; it is not a ruler. A scale properly used will last for decades, but a scale used as a straightedge will soon have the graduations worn away.”
            I have no idea what this site is, but it sure sounds authoritative!

            (by the way, these days I do my best straight line drawing with Autocad)

  2. I made one of these about 6 months ago (although in a mini combo amp style case). They sound surprisingly good, and is great for jamming in the move/camping etc. My wife also uses it to practice bass, obviously don’t get a lot of bass through small speakers but if good enough for practice proposes.

  3. I build cigar box amps all the time using the LM386. It’s pretty versatile and easy to work with for the amateur electronics person.

    Check em out at Facebook.com/scavangedsound

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