DIY Guitar Mini Amps
- Start with a pair of portable speakers (such as those sold for an MP3 player or laptop), a small karaoke machine, or compact stereo with an Mp3 or video input. Basically, any self-contained amplification unit with speakers and an input.
Ideally, find a device with built-in volume control. (Some low-end computer speakers, for example, have a fixed level and rely on the user to control the volume on the computer itself.) You might opt for a battery-powered unit for true "travel amp" functionality, but a unit with a wall plug eliminates the hassle of battery changes. - Portable karaoke machines are great finds, as they have 1/4-inch mono jacks for inputs just like a guitar amp. They accept instrument cables with no need for adapters. Furthermore, they expect a signal from a dynamic microphone (comparable to the output from passive guitar pickups) making additional devices to pre-amplify the signal unnecessary.
Other common inputs are 1/8-inch stereo jacks on Mp3-ready devices or a set of white and red RCA inputs on devices geared towards A/V systems. Computer speakers may have a lead wire ending in a 1/8-inch plug rather than a jack. - The specific components needed to plug in a guitar cable depends on your input. Units with a 1/8-inch "headphone jack" style input will need a 1/8-inch plug to 1/4-inch jack adapter. Computer speakers with a 1/8-inch lead will require a 1/8-inch jack to 1/4-inch plug adapter inline with a 1/4-inch to 1/4-inch "female to female" coupler.
If you can't determine what components you need, bring your project to an electronics store and tell a knowledgeable associate that you need to convert the input to a 1/4-inch mono jack. - If your unit is designed to take a line-out from an Mp3 player's headphone jack, you may find that your volume is low, even with the speakers cranked. Your electric guitar has passive pickups, so the signal is much quieter than the headphone-level output expected by the unit. There are a couple of ways to resolve this.
You can modify your guitar by installing active pickups. These devices require batteries and produce a powered signal. Although this high-gain output is celebrated in heavy metal circles, active pickups significantly alter guitar tones and may sound too hot or "harsh" for some.
A cheaper option (that does not require altering your guitar) is to use an effects pedal between the guitar and the speaker unit. Distortion and compression pedals in particular allow you to boost the overall volume of your signal. (Distortion for your mini-amp is an obvious bonus.) Portability is not an issue because single-effect guitar pedals can operate on either batteries or AC adapters. - With modest technical skills and creativity, you can turn this Frankenstein unit into a slick, one-of-a-kind amp.
Strip the guts out of your base unit until you have nothing but wires, circuit boards, speakers and a volume knob. Eliminate adapters by cutting off the existing input, doing the same with your effects pedal's output jack, and splicing them together. (Your pedal's "IN" jack becomes your amp's input.) Deconstruct the pedal further and swap the footswitch for a toggle or button.
Measure the surface-mounted components (speakers, switches, jacks) and build a new housing that suits you.