Little Gem MK2

Introduction

This is easy and interesting project from ROG. I needed simple and very clean amp and there were two 386s lying around so I gave it a shot. Also, having only 15×8 holes perfboard in part box I had to squeeze it as much as possible. It drives my 12″ Celestion Greenback very well, also loud enough for bedroom practice. I tried it with two 4″ 5W speakers salvaged from old Genius desktop speaker set but it sounds terrible, fizzy distorted sound all the time. I needed only clean amp so nothing is connected between pins 1 and 8 (gain control) of 386s for cleanest sound possible. There aren’t any pots or switches, volume and tone are controlled only with guitar pots. There’s no need for them because it will mostly be used as power amp only together with my Tube Reactor preamp.

Build

Enclosure is rather small (about 8x4x2cm) and it’s still half empty as you can see below. Those cutouts are done with laser and I put piece of transparent plastic (cut from CD box) below which is previously sanded for better light dispersion. Then I placed a high brightness blue LED which makes the “u-Amp” logo glow when amp is on – pretty cool, ha? There was a little problem with it since laser melted all edges and it looked really ugly, but spending some quality time with sand paper and a sharp blade I got it to look decent.

I used mix of metal film and carbon resistors found in my part box, one 47nF panasonic poly film cap and one “no name” 220nF poly cap. MOSFET is MPF102 like suggested in schematic.

Update: Since I liked this amp I tried to further improve it by shielding enclosure. I got a decent sized self adhesive copper tape for my guitar project, so lot’s of it left over for other projects like this. It is clean amp, so there isn’t noise anyway, but it might help if used with hi-gain pedal. And I also got rid of that silly tape holding that matte plastic 🙂

Clips

Considering how simple and cheap it is, it sounds pretty good. I’m not a fan of distorted sounds, as it clips kinda raspy. As long as you don’t overdrive it, clean sounds are nice. Below is a clip I recorded with my Ibanez and Mini LP. Ibanez goes first then Mini LP. The last bit is played with the IIc+ preamp making all the distortion, all others are guitar straight into the Little Gem.

Useful links

RunOffGroove.com project article

Comments
4 Responses to “Little Gem MK2”
  1. Rick says:

    Hello,
    I’ve built this on a bread board and it works but I have a lot of hum. Any ideas how I might track this problem down?

  2. Ron says:

    Hi Bane,

    I’m really interested in building a guitar amp myself. However I can’t get grip on some facts. This amp you’ve build here seems like a nice first attempt for me to recreate it.

    Some questions I have:
    I plug my guitar into the ”in” and simply connect a (descent) speaker to the out?
    Can you mail me de schematics of this amp and/or send me pictures or drawings of the layout and the wiring?
    Do I have to consider any about using/making this?

    Kind regards,
    Ron

Leave A Comment

  • About

    The idea behind this site is to share my experience with Do It Yourself approach to guitars, amplifiers and pedals. Whether you want to save a couple of bucks by performing a mod or upgrade yourself instead of paying a tech, or want to build your own piece of gear from scratch, I'm sure you will find something interesting here. Also, this is the home of DIY Layout Creator, a free piece of software for drawing circuit layouts and schematics, written with DIY enthusiasts in mind.