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POCKET SIZED GUITAR AMPLIFIER |
One of the biggest pains of an electric guitar is the need to hook it up to an amp to hear actual electric guitar sound. That's not a
problem with the milli-AMP! The milli-AMP uses a bridged ML386N-3 amplifier circuit to produce in the neighborhood of two watts
output power. It runs of a rechargeable 9 volt battery that provides an hour of full volume play per charge. At two watts, the milli-AMP is
more powerful than any commercially available amp (that I know of) of its size; its size being a very pocketable 2.25 by 3.5 by 1 inches
(roughly). Volume is controlled by the volume pot on the guitar, and controls distortion as well.
Experience Level: Intermediate | Time Required: 3-6 hours
Required tools and parts:
Case for the charger circuit: I used a case from an Ipod Nano.
Bill of Materials:
IC LM317
Transformer
Capacitor, 10uF
Battery,8.4 V
Toggle Switch
DC Power Plug, female
Plastic Cases
Prototype board
Capacitor, 1000uF
Resistors, 1.5 K
Transistor
Potentiometer, 500 OHM, single turn
Resistors, 470 OHM
Step 1 – Schematics
JAMECO PART NO. 2170521
ICLM386
Capacitor, 0.22uF
Capacitor, 0.05uF
Audio Connector
Capacitor, 100uF
DC Power Jack, male
Battery Snaps
Solid wire
Resistors, 240 OHM
Resistors, 1.5 M
Speaker
Wall transformer
Resistors, 10 OHM
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Summary of Contents for Jameco 2170521
- Page 1 POCKET SIZED GUITAR AMPLIFIER | JAMECO PART NO. 2170521 One of the biggest pains of an electric guitar is the need to hook it up to an amp to hear actual electric guitar sound. That’s not a problem with the milli-AMP! The milli-AMP uses a bridged ML386N-3 amplifier circuit to produce in the neighborhood of two watts output power.
- Page 2 The first schematic is for the amp. It has been modified from runoffgroove.com to allow for a switch and the charging jack. The original schematic can be found on the runoffgroove.com website. The second schematic is of the charger. The transistor in the charger schematic is the BC327 or equivalent.
- Page 3 1. Make sure nothing is touching here Once the circuit is built placed it in the enclosure. The battery goes at one end, with the two jacks next to the battery opposite each other, and the switch and amplifier circuit mounted underneath the speaker. Since the speaker has a relatively shallow mounting depth, there is enough room for two small heat sinks to be placed on top of the amplifier chips.
- Page 4 1. Closeup of how speaker fits above amplifying circuit 1. Heat sinks 2. Ports Step 3 – Amp: Finishing Touches - Optional I chose to add a clip from an old tape measure to the back of the amp allowing the amp to be clipped to the strap on the guitar. For a more professional appearance, the front of the amp is covered in grill cloth from an old pair of speaker grills.
- Page 5 1. Hole made for screws 1. Red dot to mark ON position of switch Step 4 – Assemble the Charger After following the schematic provided in step 1, hook the charger up to the battery in the amp. This may be easier to do with the battery removed.
- Page 6 Image Notes 1. 12 volts DC in 2. 9 volts DC out 3. The image above shows (2) 120 ohm resistors were used in the place of the 240 ohm resistor. Step 5 – Completed Project Before you use, there are a few notes about the use of the milli-AMP: Do not turn the amp on without a guitar already plugged in.