Preface

Fig.1 – The audio power amplifier with LM3886

By using the LM3886 it is possible to build a very small PCB but with the performance of the more complex and expensive commercial power audio amplifiers. Of course I’m not comparing this amplifier with some super ones available in the market, but you’ll remain amazingly surprised listening to how good it sounds.

The basic configuration suggested by the LM3886‘s data sheet works well already but it is possible to change something to make it sound better. For instance adding a few extra components to filter the signals more carefully, or, since a handful of components are necessary, it might be worth spending a little more money to buy some high quality ones.

An amazing power amplifier with the LM3886

Let’s start by listing the main characteristics of the LM3886 from the :

• s/n: ≥ 92dB;
• supply range: from 20V to 94V;
• output power: 68W to 4Ω or 38W to 8Ω (±28V);
• Total Harmonic Distortion + Noise: max 0.1%.

Fig.2 – The audio power amplifier with LM3886’s schematic

That IC is more than the core of the amplifier, it also includes other circuits to protect itself and the speakers. In particular the LM3886 provides:

• an output protection from a short to ground or to the supplies;
• an output over-voltage protection against transients from inductive loads;
• a supply under-voltage protection.

In addition the IC doesn’t get a DC pulse when it’s turned on, that means no pop sound from the speakers and no other circuits required to protect them.

Make the PCB

Fig.3 – The PCB layout

Fig.4 – The PCB mask

The PCB mask and PCB layout on the left, show how simple this project is, for that reason I suggest it to everyone, beginners and not.

Naturally if you want to build a stereo amplifier you need to make two PCBs or make as many as the channels you want.

Here are some hints and recommendations in order to make the PCB work properly.

• L1 is made twisting 12 times a 1 mm enamelled copper wire around a traditional pen.
• Before switching the amplifier on, remember to install a proper heat sink to the LM3886. In the market there exist two different versions of it: the LM3886T is not isolated, so you must interpose a mica insulator between the IC and the heat sink; otherwise the LM3886TF is already isolated so you can install it directly to the heat sink.
• Use a well filtered power supply. For a stereo project, a 100W ±28V should be fine.
• Remember to short the MUTE clamps in order to disable that function. The amplifier should work perfectly from the beginning since no calibrations are required.

 Download the project

Pressing the button below you can download a compressed file with all the necessary material to build this project:

• the LM3886 data sheet;
• pictures of the final project, the schematic, the PCB mask and the PCB layout as shown in this post;
• the schematic and the board files in Eagle format.

If you need some help please do not hesitate to contact me or leave your comments below. Enjoy it!

I have decided to share my knowledge and my projects for free, so I have not inserted any annoying ads on andy-progetti.com. Despite this, if you like my website, please help me in developing it by leaving comments and suggestions, or by making a small donation pressing the button below.

Grazie di cuore, Andrea Dal Maso

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