Amplifying your computer audio output

While using online conference applications like Adobe Connect or Skype sometimes we find some people who do not have a good microphone or do not know how to configure the audio options properly. It becomes a nightmare specially when I'm in my group classes at Englishtown or, even worse, when we are in a interview for a job application, as I did a few weeks ago.

Versão em português desse artigo: Amplificando a saída de áudio do seu computador.

Trying to solve this issue I started to search at internet for some audio amplifier devices, when I found a lot of expensive ones used by professionals and other cheaper ones being sold by Chinese people on ebay, whom I supposed to be not reliable due to how some of them replied my messages. Well, when I was almost giving up, I finally found a solution what made me to have a lot of fun dealing with.

The TDA2822M is a two channels amplifier that can be supplied directly from a 5v USB power. The related datasheet is easy to understand and comes with useful applications examples. I just picked one of those and adapted to my scenario.

Schematic and board layout

In order to build the new device it's needed the following components:

• 1x TDA2822M dual low-voltage power amplifier;
• 4x 100uf electrolytic capacitors;
• 1x 10uf electrolytic capacitor;
• 2x 100nf ceramic capacitors;
• 1x LED 3mm;
• 2x 4R7 resistors;
• 1x 470R resistor;
• 1x 10k dual-pot;
• 2x stereo phone inputs;
• 1x power jack connector for PCB;
• 1x enclosure box (PB-050 Patola Box);

To be able to use the device the following accessories will be also needed:

• 1x Stereo patch cable (easy to find assembled);
• 1x USB power cable with a jack connector (I had to build by myself).

Here is how the we've got the schematic:

Once the schematic were done, I worked in the PCB layout:

The full Eagle content, schematic and layout, can be downloaded clicking here.

The assembled device

Here is how the board looked after assembled:

In the enclosure box:

And, finally, the needed accessories:

Final considerations

Someone trying to build this device may have some difficult to find the stereo phone inputs as well as the enclosure box. I tried to find at Internet some days before going to a local components store.

It's not this post's subject to describe how to create PCBs as I already done it before (Arduino Volt-Ammeter - Final Part - Printed circuit board). But for this project I used 0.7, 0.8 and 0.9mm drill bits that made the smaller components fits much better. The Dremel's 0.8mm collet holds them perfectly for a more precise work. I also used a dimmer to decrease the minimum RPM and protect this new drill bits.

This project also has a kind of "bug". The applied dual-pot pinout inverted the volume control making it to increase when turned to counterclockwise. It was not a problem for me, but someone may want to fix this behavior.

This amplifier turned my headset volume to very high levels, so it's good to turn it totally to low before starting and then increase the volume gradually as needed.