TDA2822M Stereo Speakers with bass boost

This build was originally done in winter 2009 and I took them to the apartment the company I was working for in Geneva had let me use. There wasn't much in the way of funiture in the apartment, certainly no hifi, and a really old TV (with all programs in French or German anyway).

In the evening (after using my expenses to enjoy local restaurants), I like to listen to music without headphones and laptop speakers couldn't cut it. For a while I used my prior TDA2822M stereo speakers but I wanted a bit more of an upgrade.

The objective was to remain portable, but improve sound quality. Since I had smaller speakers, this meant I could go a little bit bigger and heavier without a problem. Unlike a hotel where I had to take everything with me when I leave for the weekend, I could leave these speakers in the apartment.

The speakers were used in the evenings frequently, and came in use once again when my company sent me to Tokyo to do some work for 4 months. This time I brought my wife with me (so no music use), but they came in handy for wathcing TV catchup in the evenings with her. The sound from these speakers is much clearer than many TVs, especially hotel (or apart-hotel) ones!

For a while they were used as speakers for the TV in the small room of our flat, so I could go there and watch Formula 1 on my own. I later upgraded that system though with a PAM8610 and some bigger speakers, so these now sit unused.

The TDA2822M was used because the TDA7052 was already getting harder to obtain and I wanted to experiment and build a bridge version. In bridge mode, the TDA2822M has double the power output, which means to stay stereo, two TDA2822M chips are needed.

Above shows the current view of them. There is an unfortunate design flaw that I've not solved properly, and that is because the boxes are fairly tall and the front screws are only in the corner, the front panel bends outward due to the pressure of the innards. This pressure is needed as without it, the box vibrates at loud volumes, pariticular with male speech. The cheap solution is to wrap tape around it.

The rear shows the connections. From left to right, a standard 3.5mm stereo jack input, a standard 2.1mm DC jack for the power input, and a small mono 2.5mm jack for the output to the second speaker. The second speaker can house batteries and thus has a 2.1mm DC output jack, and the single 2.5mm jack speaker input.

Inside are the speakers. The tweeter is overkill for the job really (and isn't particularly needed either), but was rescued from some old speakers so cost nothing. The Visaton FRS 7 S woofer is a 2.5" full range speaker, which has good performance for its size.

Inside the case is the TDA2822M bridged amplifier, based on the datasheet version. Some stick on heatsinks were applied to help dissapate heat when the chips are pushed hard. On the middle right is a bass boost circuit, described in this bass boost article. It's the single supply inverting version I used here, and this certainly helps the speakers sound more 'full'. A small board was built for the power and speaker out jacks, with a 1000uF capacitor to smooth out the voltage from cheap PSUs better, and ferrite bead to reduce noise from the same.

Looking closer at the amp, you can see the various connections - and a design flaw where I forgot to bear in mind the size that LED power switch takes, so had to adjust a capacitor and heatsink a bit!

The underside of the board shows the PCB layout I used. You can feel free to copy that if you like. It is not based on the datasheet as I wanted all connections to be on one side of the board for access, as well as have the stereo volume control on the board (as I can use it to mount the board to the box).

These speakers have done me well over 9 years but now unsued (I've built too many I think!) until they were replaced by the PAM8403 speakers. I would like to trasplant these to better boxes when I've a use for them, but for now, I hope someone will find this read of some small interest!