Pocket Sized Mobile Phone Amplifier !!!!

Even though I do not know from experience- (as I do not play the guitar)- I have heard from many of my friends that 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. Thats not a problem with the Milli-AMP!

Product pitching aside, this is a pretty neat project for somebody with beginner's electronics skill that can follow a schematic. I will state now that the circuit is not of my own design, but is a modified Little Gem Mk II circuit from runoffgroove.com. I would recommend checking out the site for some other pretty cool music-related schematics. Even though the circuit is not mine, the design of the enclosure and the charging circuit is of my own creation.

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, which provides about 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 pocket able 2.25 by 3.5 by 1 inches (roughly). Volume is controlled by the volume pot on the guitar, and this adversely controls distortion as well. For an idea of what it sounds like, see the last step of this instruct able .



PART 1 (Material Required) 

The Milli-AMP uses readily available parts, most available at just about any electronic component retailer. The list of parts below includes the part numbers for allelectronics.com, which is one of my go-to suppliers of components. The list of parts is as follows, and is not only for the Milli-AMP, but for the charger as well:

Perf board: PC-1
1/4" Mono Jack: PHJ-S
12.5 VDC Wall Transformer: DCTX-1285
2.1 mm Coax Power Jack: DCJ-21
2.1 mm Coax Power Plug: DCSID
9 Volt Battery Snaps: BST-3
Black Plastic Case: 1951-MSBK
SPDT Toggle Switch: MTS-542
Miniature Full Range Speaker: SK-408
9v 250 mah NiMh Battery: NMH-925
LM386 Amp: LM386N
500 ohm Trim Pot: TPS-500
LM317 Volt Regulator: LM317T

Also needed:
MPF102 Transistor: Radio shack part# 276-2062
BC327 Transistor: I had one of these lying around. An equivalent transistor can be substituted
10 ohm, 10K ohm, 1.5M ohm, 240 ohm, 1.5K ohm, 470 ohm Resistors: Scavenged, or purchased from Radio shack/ All Electronics.
0.22 uf, 100 uf 16v, 10uf 16v (x2), 0.05 uf, 1000 uf 25v capacitors: Scavenged, or purchased from Radio shack/ All Electronics.
Hookup wire
Case for the charger circuit: I used a case from an Ipod Nano.


A note about some of the parts: The speaker listed is the only one i would recommend for this project since it has a resistance of 8 ohms (Nothing lower should be used) and can handle 3 watts. It is also about 1.5 inches wide. Unless you can find something that meets these specs, stick with the speaker listed. Also, I cannot guantee you will receive LM386N-3 amplifiers. The last number after the dash signifies power output level, with 1 being the weakest and 4 being the most powerful. While different amplifiers will lead to different performance, as long as they both have the same last digit, they can be wired into the circuit without modification. 

STEP2 (Schematics) 

 

 This is Amplifier Circuit and Can be easily Constructable and adjustable due to its compact Size 

 

 

This is the Charger Circuit.
  

SOME SCREENSHOT OF THE ASSEMBLED PROJECT