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LM3886 Chip Amplifier

LM3886 Chip Amplifier

Posted on by George Czabania

Building a Chip Amplifier

In preparation to this project, I built a LM380 chip amp, which was cheaper and easier and makes for a good weekend project.


Project Goal

I want to build an amplifier. Mainly because I need something to connect an iPhone to a set of speakers.

Warning: This project requires working with mains supply voltages, which can be lethal if you don’t take the proper precautions.

My original idea was to use a LM386 IC and $20 worth of parts to make a 0.5W amp powered using 12v, but now I’m thinking I need to make something with a bit more oomph.

Then I discovered the gainclone amplifier, which appears to be quite popular in the DIY audio community.

After researching different circuits and variations, I settled on the kitset from chipamp.com. I chose the Non-Inverting LM3886 stereo kit, which included a ‘snubberized’ power supply board, and was also on special.

However, the kit supplys only the parts for the power supply board and the two amplifiers. There is still quite a lot you need to do.

The Chipamp Kit

All the parts meticulously laid
out

The Full Bridge Rectifier

This converts AC to DC using a bunch of diodes in a clever pattern. I’m going to go for the ‘snubberized’ version.

The circuit is based on one developed by Carlos Machado, which allows it drive more difficult loads without adversly affecting the midrange and top end sound. More information here.

There are two identical circuits, each with a full bridge rectifiers. The dual circuits are for the left and right audio channels.

Parts list (included with kit):

2x 10000 uF 50v Panasonic TS Capacitors (35mm x 30mm low profile)
4x 0.1 uf film caps
8x MUR860 On Semiconductor Diodes
2x 2.2 kohm 2w metal film resistors
2x 1 ohm 2w metal film resistors
1x blue LED
1x 1N4004 diode
1x 10 kohm 0.5w compact metal film resistor
1x 10 uF Panasonic FC Capacitors

Amplifier

Parts list (included with kit):

2x LM3886TF
4x 22 kohm 0.5w compact metal film resistors
2x 10 kohm 0.5w compact metal film resistors
2x 1 kohm 0.5w compact metal film resistors
2x 680 ohm 0.5w compact metal film resistors
2x 2.7 ohm 2w metal film resistors
6x 100 uf 50v Panasonic FC
2x 47 uf 50v Panasonic FC
6x 0.1 uf film caps

The Power Supply

This is pretty important. You don’t want to just use any old power supply, because it will likely introduce a humming sound to audio output. I decided to use a toroidal transformer.

225VA 2x25V AC Toroidal Transformer

Recommended reading: Decible Dungeoun - Building a PSU.

Required Components

Preamplifier

Preamplifier Power

Trying it out

The Box

Installing Components in Box

Complete

Bonus Shots