GUITAR BOOSTER AMP

This tiny unit acts not only as a practice amplifier, allowing you to listen to your guitar through headphones, but it functions also as a pre- amplifier so you can connect to any sound system that has auxiliary input. Small enough to fit in your pocket but it allows really big sound at minimal cost as you don’t have to buy or lug around a heavy guitar amp. It is based on an LM386 integrated circuit amplifier circuit, hence the small size.

Materials:

There are lots of Instructables featuring LM386 amplifiers. Most would work here. I built this one instead as all the parts are supplied, it’s cheap and it comes with a printed circuit board:

- Mini Electronic DIY LM386 Amplifier Module Kit- (Available from Amazon for about $8 CDN)

9V Battery clip

9v battery

hook up wire

on/off switch

1/4” male monaural audio jack

1/8” female monaural audio socket

washers to fit jack and socket

transparent project box (3”x 2,3/4”- snap lid food container)

1/4” male to male audio cord-6 feet (optional for connection to external sound system)

Epoxy glue

Double sided tape

Tools: Soldering iron, fine electrical solder, needle nose pliers, wire cutters, strippers, Drill with step bit.

Lay out all the parts from the kit. Discard the included sockets as you will be soldering the power, input and output directly to the board.

Assembly is easy as the circuit board is clearly marked with actual size icons of the parts with proper polarities. Make all solder connections quickly to avoid overheating the components.

Work in stages: Begin by installing and soldering the potentiometer and IC socket in place.

Next install the electrolytic capacitors, solder and snip off the excess wire. Watch the polarities- they are well marked.

Install the LED. Short lead is negative. Solder and snip.

Install the disc capacitors next, then the resistors. (Be careful, one resistor is different. Watch the values on the board.) Solder and snip.

Last step: Solder the 1/8” socket leads to the “SPKR” terminals, the 9V battery clip to the + and- terminals and a piece of hook up wire to each of the AUDIO terminals.

Plug the LM386 module into its socket. Match the notches.

You may run a test by temporarily soldering the audio wires to the jack terminals. Attach the battery, the LED should light. Plug into your guitar, attach the headphones, turn the pot to max. Strum your guitar. If you don’t hear anything, check your solder connections.

Drill the hole for the jack off centre in the bottom of the box. Drill holes for the switch, socket and amplifier in the lid of the box. Remember, you need room for the battery so locate the components strategically.

Install the amplifier with its included nut and washer. Install your switch. I glued the jack and socket in place with epoxy and reinforced with washers so they would be solid against the thin plastic.

Cut the red wire from the battery. Strip the ends and solder to the switch terminals. Strip and solder the audio input wires to the jack terminals. Attach the battery clip to the battery. Attach some double sided tape to the battery and stick it to the bottom of the box where it will not interfere with the other components. Replace the lid then switch on and test. The red LED should be visible through the transparent box and remind you the unit is on. Plug the amp module into your guitar, plug the phones into the amp. Switch on and you should hear great audio. Plug a patch cord into the output and connect to your stereo if you want everyone to hear it.